No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Influence of Viscous, Gravitational, and Capillary Forces on DNAPL Saturation
Abstract
Four dense nonaqueous phase liquids (DNAPLs)—bromoform, chlorobenzene, tetrachloroethylene, and trichloro‐ethylene—were used to investigate the influence of viscous, gravitational, and capillary forces on DNAPL saturation in a natural aquifer sand. The relative magnitudes of these forces are expressed in terms of two dimensionless groups, the Capillary Number (N Ca ), defined as the ratio of the viscous force to capillary force, and the Bond Number (N Bo ), defined as the ratio of the gravitational force to capillary force.
Nondimensionalization of the equations governing two‐phase flow suggests that DNAPL saturation should be a function of a linear combination of the Capillary and Bond Numbers (N Ca /k rw — N Bo ), provided the permeability to water (k rw ) in the presence of discontinuous DNAPL is considered. Experimental studies in which DNAPL saturations were measured over a range of Capillary and Bond Numbers for upward, horizontal, and downward displacement of DNAPL by water corroborate the results of the nondimensionlization. DNAPL saturations generally decreased with increasing Capillary Number and with decreasing Bond Number until N Ca /k rw — N Bo was greater than approximately 1 × 10 ‐5 at which point residual saturation was attained. For the DNAPLs used in this study, with adhesion tensions on the order of 26 dynes/cm and Bond Numbers ranging from 1.3 × 10 ‐7 to 2.4 × 10 ‐6 , residual saturation was attained at Capillary Numbers greater than approximately 5 × 10 ‐5 . These results provide a means of estimating the system conditions under which the DNAPLs studied achieve residual saturation in aquifer material.
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
... 1.62 Dawson and Roberts (1997) μ n (cp) 0.9 Dawson and Roberts (1997) CMC of SDS (mol/L) 0.008 Harendra and Vipulanandan (2011) MW of SDS (g/mol) 288.37 CMC of TX100 (mol/L) 0.0002 Harendra and Vipulanandan (2011) MW of TX100 (g/mol) 647.00 Dm(cm 2 /s) 9.4 × 10 − 6 Wilke and Chang (1955) σ0 (mN/ m) 44 Dawson and Roberts (1997) θ 20 Chomsurin and Werth (2003) Γm(mol /m 2 ) 1.45 × 10 − 6 Karakashev et al. (2008) Knw(m 3 /mol) 3.6 × 10 3 a i can be applied in different porous media and flow rates in order to evaluate distribution of entrapped NAPL blobs and ganglia at similar NAPL saturations (Corapcioglu et al., 2009;Saripalli et al., 1997;Wu et al., 2016). The significant changes in a i at lower NAPL saturations show that surfactant flooding could change NAPL distribution in porous media. ...
In this paper, the dissolution and mobilization of non-aqueous phase liquid (NAPL) blobs in the Surfactant-Enhanced Aquifer Remediation (SEAR) process were upscaled using dynamic pore network modeling (PNM) of three-dimensional and unstructured networks. We considered corner flow and micro-flow mechanisms including snap-off and piston-like movement for two-phase flow. Moreover, NAPL entrapment and remobilization were evaluated using force analysis to develop the capillary desaturation curve (CDC) and predict the onset of remobilization. The corner diffusion mechanism was also applied in the modeling of interphase mass transfer to represent NAPL dissolution as the dominant mass transfer process. In addition, the effect of pore-scale heterogeneity on mass transfer rate coefficient and recovered residual NAPL was considered in the simulations. Sodium dodecyl sulfate (SDS) and Triton X-100 were used as the surfactant for the SEAR process. The results indicate that although surfactants enhance NAPL recovery during two-phase flow, surfactant-enhanced remediation of residual NAPL through dissolution is highly dependent on surfactant type. When SDS ─as a surfactant with high critical micelle concentration (CMC) and low micelle partition coefficient (Km)─ was injected into a NAPL contaminated site, the mass transfer rate coefficient decreased (due to considerable changes in interface chemical potentials) which leads to a significant reduction in NAPL recovery after the end of two-phase flow. In contrast, Triton X-100 (with low CMC and high Km) improved NAPL recovery, by enhancing solubility at surfactant concentrations greater than CMC which overcompensates the interphase mass transfer reduction.
... The correlation between Ca N and residual saturation, rn S , has been widely studied. A typical correlation between Ca N and rn S is shown in Figure 2.16 (Dawson et al., 1997) Figure 2. 16 NAPL saturation as a function of Ca N (Dawson et al., 1997) The Bond number, Bo N , is the ratio of buoyancy (gravitational) to capillary forces and can be expressed as: ...
... The correlation between Ca N and residual saturation, rn S , has been widely studied. A typical correlation between Ca N and rn S is shown in Figure 2.16 (Dawson et al., 1997) Figure 2. 16 NAPL saturation as a function of Ca N (Dawson et al., 1997) The Bond number, Bo N , is the ratio of buoyancy (gravitational) to capillary forces and can be expressed as: ...
... where ρ ∆ is the density difference between the two immiscible fluids, g is the gravitational acceleration constant, R is a characteristic medium size, and σ is the interfacial tension between the two immiscible fluids. Bo N can be also defined in terms of the absolute permeability of the porous medium, k : (Dawson et al., 1997) Actually, viscous and gravitational forces are acting on a trapped NAPL blob simultaneously, such that a trapping number, T N , defined as the vectorial sum of capillary number and Bond number, is used to measure the combined influence of viscous and gravitational forces (Gioia et al., 2006;Li et al., 2007;Pennell et al., 1996;Longino et al., 1999). The trapping number, T N , derived by Pennell et al. (1996) is given as: ...
... Ewing and Berkowitz (1998) noted that the phase diagram relating viscous, capillary, and stable flow regimes should contain a third dimension to account for gravity and buoyancy forces, given by the Bond number N b . The quantitative parameters previously described have also been applied to estimate the mobility of DNAPLs in porous media in terms of temporal variation of DNAPL saturation profiles during immiscible displacements (Pennell et al., 1996; Helen and Paul, 1997; Hunt et al., 1998; Theodoropoulou et al., 2005; Glen et al., 2006). Several methods have been used to study fluid saturations during the immiscible fluid displacement process. ...
... For a high initial TCE saturation in the porous medium (66%), the remaining TCE saturation is only 18% for downward water-flooding against 45% when a upward waterflooding was applied. This result is in good agreement with the findings of Helen and Paul (1997) . In the case of upward waterflooding , the viscous forces are counteracted by buoyancy forces at the lowest water-flooding rates, and a large fraction of the TCE remains in the pores. ...
... Ewing and Berkowitz (1998) noted that the phase diagram relating viscous, capillary, and stable flow regimes should contain a third dimension to account for gravity and buoyancy forces, given by the Bond number N b. The quantitative parameters previously described have also been applied to estimate the mobility of DNAPLs in porous media in terms of temporal variation of DNAPL saturation profiles during immiscible displacements ( Pennell et al., 1996;Helen and Paul, 1997;Hunt et al., 1998;Theodoropoulou et al., 2005;Glen et al., 2006). Several methods have been used to study fluid saturations during the immiscible fluid displacement process. ...
... where v is the superficial velocity of the displacing fluid, μ is the dynamic viscosity of the displacing fluid, and σ is the interfacial tension between the two fluids. Many researchers have examined the relationship of the capillary number (both N C = μv/σ and other variant N C = k r k p/L σ , where k r and k are respectively the relative and intrinsic permeabilities and p/L is the pressure gradient) to the residual saturation, and obtained critical capillary numbers required for initiation and complete mobilization of trapped NAPL in various porous media Chevalier and Fonte, 2000;Dawson and Roberts, 1997;Morrow et al., 1988;Morrow and Songkran, 1981;Ng et al., 1978;Pennell et al., 1996;Wardlaw and McKellar, 1985). Critical capillary numbers (N C = μv/σ ) required for initiation and complete mobilization of trapped NAPL in sandstone are of the order of 10 −6 and 10 −3 respectively, while the critical capillary number for glass beads are of the order of 10 −4 and 10 −2 respectively . ...
... 4. Other variants of the Bond number based on intrinsic permeability (k) are also used in the literature (Chevalier and Fonte, 2000;Morrow and Songkran, 1984;Wilson and Conrad, 1984): N B = k ρg σ . Some researchers have included a porosity term in the capillary and Bond numbers (Dawson and Roberts, 1997). In this case, the additional dimensionless term with a value less than one would change these numbers significantly (Chevalier and Fonte, 2000). ...
... In this case, the additional dimensionless term with a value less than one would change these numbers significantly (Chevalier and Fonte, 2000). The previous formulations are based on a zero contact angle (θ = 0 • ) at the solid-water-NAPL interface; nonzero contact angle relationships are also included by some authors (Dawson and Roberts, 1997;Li et al., 2001;Pennell et al., 1993;Pennell et al., 1996): N B = kk r w ρg (σ cos θ) & N C = μv (σ cos θ ). ...
The frequent use of non-aqueous phase liquids (NAPLs) in cold regions creates serious risks of soil and groundwater contamination. NAPL contaminants can stay in soil for long times due to their entrapment by strong interfacial forces, resulting in a source of pollution caused by their slow dissolution in groundwater over decades. The presence of these contaminants in ice-containing soils creates a four-phase problem, which must be fully understood to design/develop or improve remediation techniques in cold climate regions. In this review, the fate and transport of NAPL contaminants in periodically freezing-thawing and frozen soils is discussed, with emphasis on pore-scale processes. Three topics are identified for future research focus: (i) study of the dynamics of NAPLs during freezing and thawing of soils using non-destructive imaging techniques, and the effect of various factors, including wettability, pore size, consolidation of porous matrix and fluid properties; (ii) investigations of the fate and transport of NAPL contaminants in frozen soils with different wettabilities, and the effect of the spatial distribution of ice clusters on NAPL retention and movement; and (iii) pore-scale modeling of the fate and transport of NAPL spills in freezing-thawing and frozen soils. This will lead us towards a complete pore-scale understanding of NAPL spills in cold climate soils, and their fate and transport over time.
... Immiscible multiphase flows in porous media represent one of the most challenging flow systems to study with optical diagnostics [6]. These flows are central to a range of industrial and environmental processes, including enhanced oil recovery (EOR) [7], ground water remediation [8], water management in fuel cells [9] and carbon capture and storage [10]. Numerical methods to study the pore-scale physics near the meniscus struggle due to the strong instabilities characterising phase discontinuities where capillary forces play a crucial role. ...
... The development of this methodology was inspired by ongoing high-speed µPIV measurements of liquid CO 2 -water multiphase flow in 2D porous micromodels, which is of fundamental importance in geologic CO 2 sequestration as well as EOR and ground water remediation [7,8]. In brief, the goal of such studies is to quantify the pore-scale flow of water and liquid CO 2 as well as the dynamics of the interface between these two immiscible fluid phases in 2D micromodels (For more details on such efforts, the reader is referred to [6, 11-15, 42, 43]). ...
Particle image velocimetry (PIV) is a valuable tool for experimentally studying multiphase flows. In order to distinguish the flow dynamics of each individual phase, proper image segmentation must be performed. In immiscible multiphase flows, the fidelity of phase segmentation is directly linked to the accuracy of the interface detection. This paper reports a novel method for robust phase separation and phase boundary identification applicable to particle images acquired via PIV. The method, which requires a seeding density differentiation between the phases, is based on particle detection and triangular meshing. In this method, tracer particles in all seeded phases are first identified, and the coordinates of the particle locations are then used to formulate a 2D unstructured mesh, where the triangular grids provide the basis for phase separation and the outer edges provide a basis for interface detection. This paper presents a parametric analysis on synthetic particle images to assess the performance of the method and to compare the results to existing approaches. In addition, an application to experimentally generated images is reported. These results show that this method can successfully track the complex interface evolution in a particularly challenging flow system consisting of immiscible multiphase flow in porous media.
... The relative strength of capillary forces are described using the Capillary (Ca) and Bond (Bo) numbers, defined respectively as the ratios of viscous to capillary and gravity to capillary forces. Ca and Bo values were estimated from equations (1) and (2) (Dawson & Roberts, 1997;Herring et al., 2016): ...
... These relationships are only valid for the contact angle range of 0<|θ|<90°. The estimated Ca numbers, using the relationship from Dawson and Roberts (1997), are 6.3 × 10 −5 and 2.9 × 10 −5 for the IW and WW sands, respectively. The Bo numbers, estimated using a relationship from Herring et al. (2016), are 0.14 and 0.064 for the IW and WW sands, respectively. ...
The pore‐scale processes governing water drainage behavior in porous media have implications for geoscience multiphase scenarios including carbon capture and storage, contaminant site remediation, oil recovery, and vadose zone processes. However, few studies report directly observed pore‐scale water drainage phenomena in 3‐D soils. This knowledge gap limits our ability to verify assumptions underlying existing models and develop optimal solutions. This paper utilizes synchrotron X‐ray microtomography to present an experimental pore‐scale examination of nonaqueous phase liquid (NAPL)/water distribution along a primary drainage front as dense NAPL was injected upward into water wetting (WW) and intermediate wetting (IW) sand‐packed columns. Pore‐network structures were extracted from imaged data sets and mapped onto segmented NAPL/water data sets which allowed quantitative examinations of wettability impacts on (a) the extent to which NAPL fills individual pore bodies and (b) relationships between pore size and the phase occupying the pore, with both considered as a function of distance (and capillary pressure) relative to the NAPL front. These results revealed that several hypotheses treating IW sand similarly to WW sands are simplistic. IW systems exhibited a sequence of pore filling that deviated from traditional capillary pressure‐based model predictions: NAPL invades smaller pores, while larger, adjacent pores are bypassed leaving multipore residual water ganglia. NAPL pore saturations were close to 1 and did not change with capillary pressure in IW systems. Overall, the results illustrate how a relatively small change in operative contact angle alters NAPL distribution during water drainage, with important implications for geoscience multiphase flow scenarios.
... Unfortunately, with the rapid development of economic activities such as mining, agriculture, landfills and industrial activities (Bakshevskaia and Pozdniakov, 2016;Cui et al., 2016;H. Liu et al., 2016;An et al., 2016;Shen et al., 2017), more and more contaminants released from human activities are contaminating the precious groundwater resource and subsurface environment (Dawson and Roberts, 1997;Liu, 2005;Hadley and Newell, 2014;Carroll et al., 2015;Essaid et al., 2015;Huang et al., 2015;Schaefer et al., 2016;Weathers et al., 2016). Among the contaminants detected in groundwater, dense nonaqueous phase liquids (DNAPLs) such as perchloroethylene (PCE) and other polycyclic aromatic hydrocarbons (PAHs), are highly toxic and carcinogenic (Dawson and Roberts, 1997;Hadley and Newell, 2014). ...
... Liu et al., 2016;An et al., 2016;Shen et al., 2017), more and more contaminants released from human activities are contaminating the precious groundwater resource and subsurface environment (Dawson and Roberts, 1997;Liu, 2005;Hadley and Newell, 2014;Carroll et al., 2015;Essaid et al., 2015;Huang et al., 2015;Schaefer et al., 2016;Weathers et al., 2016). Among the contaminants detected in groundwater, dense nonaqueous phase liquids (DNAPLs) such as perchloroethylene (PCE) and other polycyclic aromatic hydrocarbons (PAHs), are highly toxic and carcinogenic (Dawson and Roberts, 1997;Hadley and Newell, 2014). When DNAPLs are released into aquifer from underground storage tanks, they will infiltrate through the entire aquifer and form residual ganglia and pools of DNAPLs due to their large densities, high interfacial tension, and low solubility. ...
Groundwater can be stored abundantly in granula-composed aquifers with high permeability. The microstructure of granular materials has important effect on the permeability of aquifers and the contaminant migration and remediation in aquifers is also influenced by the characteristics of porous media. In this study, two different microscale arrangements of sand particles are compared to reveal the effects of microstructure on the contaminant migration and remediation. With the help of fractal theory, the mathematical expressions of permeability and entry pressure are conducted to delineate granular materials with regular triangle arrangement (RTA) and square pitch arrangement (SPA) at microscale. Using a sequential Gaussian simulation (SGS) method, a synthetic heterogeneous site contaminated by perchloroethylene (PCE) is then used to investigate the migration and remediation affected by the two different microscale arrangements. PCE is released from an underground storage tank into the aquifer and the surfactant is used to clean up the subsurface contamination. Results suggest that RTA can not only cause more groundwater contamination, but also make remediation become more difficult. The PCE remediation efficiency of 60.01–99.78 % with a mean of 92.52 and 65.53–99.74 % with a mean of 95.83 % is achieved for 200 individual heterogeneous realizations based on the RTA and SPA, respectively, indicating that the cleanup of PCE in aquifer with SPA is significantly easier. This study leads to a new understanding of the microstructures of porous media and demonstrates how microscale arrangements control contaminant migration in aquifers, which is helpful to design successful remediation scheme for underground storage tank spill.
... Interfacial effects play an important role in governing multiphase fluid behavior in porous media (Neustadter 1984; Tuck et al. 1988). For instance, several dimensionless numbers have been developed to express important force ratios applicable to multiphase flow in porous media (Morrow and Songkran 1981; Chatzis and Morrow 1984; Wardlaw 1988; Pennell et al. 1996; Dawson and Roberts 1997). These force ratios emphasize the importance of interfacial properties. ...
... Total trapping number is the ratio of the summed mobilizing forces (viscous and buoyancy) to the resistive force (capillary). Dawson and Roberts (1997) derived similar equations. The importance of fluid force ratios make knowledge of the fluid-fluid interfacial tension essential when conducting or interpreting experiments on multiphase fluid flow in porous media (Tuck, Discussion of "DNAPL migration through a fractured perching layer" by Daniel B. Stephens, James A. Kelsey, Mark A. Prieksat, Mel G. Piepho, Chao Shan, and Mark D. Ankeny, accepted for publication in Ground Water). ...
Interfacial effects play an important role in governing multiphase fluid behavior in porous media (Neustadter 1984; Tuck et al. 1988). For instance, several dimensionless numbers have been developed to express important force ratios applicable to multiphase flow in porous media (Morrow and Songkran 1981; Chatzis and Morrow 1984; Wardlaw 1988; Pennell et al. 1996; Dawson and Roberts 1997). These force ratios emphasize the importance of interfacial properties. Our objectives are to provide chemical information regarding the dyes commonly used in multiphase flow visualization studies and to show the surface chemistry effects of the most commonly used dye, Sudan IV, in the tetrachloroethylene (PCE)-water-glass system
... Drainage is the process by which a nonwetting fluid displaces a wetting fluid from a porous medium. It underlies a broad range of environmental and industrial processes, including groundwater contamination, oil migration and recovery, gas venting from sediments, CO 2 sequestration, soil drying, and the operation of porous membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Therefore, extensive research has sought to develop ways to predict the displacement pathway taken by the nonwetting fluid [18,19], building on the seminal model of invasion percolation proposed by Wilkinson and Willemsen four decades ago [20]. ...
Drainage, in which a nonwetting fluid displaces a wetting fluid from a porous medium, is well studied for media with unchanging solid surfaces. However, many media can be eroded by drainage, with eroded material redeposited in pores downstream, altering further flow. Here we use theory and simulation to examine how these coupled processes both alter the overall fluid displacement pathway and help reshape the solid medium. We find two drainage behaviors with markedly different characteristics and quantitatively delineate the conditions under which they arise. Our results thereby help expand the current understanding of these rich physics, with implications for applications of drainage in industry and the environment.
... With the development of the social economy and urbanization, extensive use of dense non-aqueous phase liquids (DNAPLs) in the industry has led to serious groundwater environment deterioration, which has become one of the hotspots that attracted attracting global attention [1][2][3][4][5][6][7][8]. When these toxic, carcinogenic, and less easily degraded DNAPLs cause groundwater contamination, the ecosystem and human health are seriously threatened [9][10][11][12]. DNAPLs are heavier than water and usually migrate downward through the saturated zone due to their greater density. ...
Investigation of the change rate for contaminant parameters is important to characterize dense non-aqueous phase liquid (DNAPL) transport and distribution in groundwater systems. In this study, four experiments of perchloroethylene (PCE) migration are conducted in two-dimensional (2D) sandboxes to characterize change rates of PCE saturation (So) and PCE–water interfacial area (AOW) under different conditions of salinity, surface active agent, and heterogeneity. Associated representative elementary volume (REV) of the change rate of So (So rate) and change rate of AOW (AOW rate) is derived over the long-term transport process through light transmission techniques. REV of So rate (SR-REV) and REV of AOW rate (AR-REV) are estimated based on the relative gradient error (εgi). Regression analysis is applied to investigate the regularity, and a model based on a back-propagation (BP) neural network is built to simulate and predict the frequencies of SR-REV and AR-REV. Experimental results indicated the salinity, surface active agent, and heterogeneity are important factors that affect the So rate, AOW rate, SR-REV, and AR-REV of the PCE plume in porous media. The first moment of the PCE plume along the vertical direction is decreased under conditions of high salinity, surface active agent, and heterogeneity, while these factors have different effects on the second moment of the PCE plume. Compared with the salinity and surface active agent, heterogeneity has the greatest effect on the GTP, the distributions of the So rate and AOW rate along the depth, and dM, dI. For SR-REV, the standard deviation is increased by the salinity, surface active agent, and heterogeneity. Simultaneously, the salinity and heterogeneity lead to lower values of the mean value of SR-REV, while the surface active agent increases the mean value of SR-REV. However, the mean and standard deviation of AR-REV have no apparent difference under different experimental conditions. These findings reveal the complexity of PCE transport and scale effect in the groundwater system, which have important significance in improving our understanding of DNAPL transport regularity and promoting associated prediction.
... Drainage is the process by which a nonwetting fluid displaces a wetting fluid from a porous medium. It underlies a broad range of environmental and industrial processes, including groundwater contamination, oil migration and recovery, gas venting from sediments, CO 2 sequestration, soil drying, and fluid transport in porous membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Therefore, extensive research has sought to develop ways to predict the displacement pathway taken by the nonwetting fluid [18,19], building on the seminal model of invasion percolation proposed by Wilkinson and Willemsen four decades ago [20]. ...
Drainage, in which a nonwetting fluid displaces a wetting fluid from a porous medium, is well-studied for media with unchanging solid surfaces. However, many media can be eroded by drainage, with eroded material redeposited in pores downstream, altering further flow. Here, we use theory and simulation to examine how these coupled processes both alter the overall fluid displacement pathway and help reshape the solid medium. We find two new drainage behaviors with markedly different characteristics, and quantitatively delineate the conditions under which they arise. Our results thereby help expand current understanding of these rich physics, with implications for applications of drainage in industry and the environment.
... The flow of immiscible fluids in porous media is a common process in many natural and engineering settings, such as geological carbon sequestration [1,2], enhanced oil recovery [3,4], and groundwater contamination [5,6]. Understanding and controlling the instability of the fluid-fluid interface are beneficial for increasing the efficiency of oil recovery and CO 2 sequestration [7][8][9][10][11][12][13]. ...
The displacement of immiscible fluids in porous media is common in many natural processes and engineering applications. Under quasi-static conditions, the displacement is affected by the geometry of the porous media and wetting condition. In an ordered porous medium, i.e., the pore size is maintained constant in the transverse direction and changes monotonously from the inlet to the outlet; previous works always focused on pore size gradient, but the role of wettability is not well-understood. Here, we investigate the pattern transition in ordered porous media with positive and negative pore size gradients under the wetting condition from imbibition to drainage. We first study the onsets of pore-filling events and then establish a link between these events and the local invasion morphologies at multiple pores under quasi-static conditions. We show that the burst and touch events, previously recognized to destabilize the displacement front, can cause a stable front in the negative and positive gradient porous media. We then link the local invasion morphologies to the displacement patterns, including the compact pattern, taper shape pattern, kite shape pattern, and single-fingering pattern. We propose a model to predict the transitions of these four patterns directly. The model prediction shows that the decreases in contact angles would destabilize the displacement front in the negative gradient porous media and stabilize the displacement front in the positive gradient porous media. We evaluate the predictive model using pore network simulations in this work and experiments in the literature, confirming that it can reasonably predict the pattern transition for immiscible displacements in ordered porous media under quasi-static conditions. Our work extends the classic phase diagram in ordered porous media and is of practical significance for multiphase flow control.
... Immiscible fluid displacement is controlled by capillary force F C , viscous force F D , and the buoyant force F b . Critical dimensionless numbers are the capillary number, the viscous ratio and the Bond number (Chatzis and Morrow, 1984;Lenormand et al., 1988;Dawson and Roberts, 1997;Ferer et al., 2004;Santamarina and Jang, 2011; Patterns observed during immiscible fluid invasion (i.e., nonwetting) fall into domains defined by these dimensionless numbers: stable displacement takes place at large M and Ca; viscous fingering at small M and large Ca; and capillary fingering at large M and small Ca (Figure 7). The Rayleigh-Taylor instability, observed when a lighter fluid ascends through a heavier fluid, develops at large Bond numbers. ...
Single and multi-phase fluids fill the pore space in sediments; phases may include gases (air, CH 4 , CO 2 , H 2 , and NH 3 ), liquids (aqueous solutions or organic compounds), and even ice and hydrates. Fluids can experience instabilities within the pore space or trigger instabilities in the granular skeleton. Then, we divided fluid-driven instabilities in granular media into two categories. Fluid instabilities at constant fabric take place within the pore space without affecting the granular skeleton; these can result from hysteresis in contact angle and interfacial tension (aggravated in particle-laden flow), fluid compressibility, changes in pore geometry along the flow direction, and contrasting viscosity among immiscible fluids. More intricate fluid instabilities with fabric changes take place when fluids affect the granular skeleton, thus the evolving local effective stress field. We considered several cases: 1) open-mode discontinuities driven by drag forces, i.e., hydraulic fracture; 2) grain-displacive invasion of immiscible fluids, such as desiccation cracks, ice and hydrate lenses, gas and oil-driven openings, and capillary collapse; 3) hydro-chemo-mechanically coupled instabilities triggered by mineral dissolution during the injection of reactive fluids, from wormholes to shear band formation; and 4) instabilities associated with particle transport (backward piping erosion), thermal changes (thermo-hydraulic fractures), and changes in electrical interparticle interaction (osmotic-hydraulic fractures and contractive openings). In all cases, we seek to identify the pore and particle-scale positive feedback mechanisms that amplify initial perturbations and to identify the governing dimensionless ratios that define the stable and unstable domains. A [N/m] Contact line adhesion
... Multiphase flow in porous media is ubiquitous in natural systems as well as engineering applications, such as enhanced oil recovery (EOR) (Simjoo et al., 2013), ground water remediation (Dawson and Roberts, 1997), water management in fuel cells (Bazylak, 2009) and carbon capture and storage (CCS) (Huppert and Neufeld, 2014). Notably, the sequestration of carbon dioxide (CO 2 ) in deep saline aquifers is considered to be a viable technology to reduce carbon emissions into the atmosphere as a means of mitigating green house effect (Koide et al., 1992;Gunter et al., 1997;Bachu, 2000;Pacala and Socolow, 2004;Huppert and Neufeld, 2014). ...
Resolving pore-scale transient flow dynamics is crucial to understanding the physics underlying multiphase flow in porous media and informing large-scale predictive models. Surface properties of the porous matrix play an important role in controlling such physics, yet interfacial mechanisms remain poorly understood, in part due to a lack of direct observations. This study reports on an experimental investigation of the pore-scale flow dynamics of liquid CO 2 and water in two-dimensional (2D) circular porous micromodels with different surface characteristics employing high-speed microscopic particle image velocimetry (μPIV). The design of the micromodel minimized side boundary effects due to the limited size of the domain. The high-speed μPIV technique resolved the spatial and temporal dynamics of multiphase flow of CO 2 and water under reservoir-relevant conditions, for both drainage and imbibition scenarios. When CO 2 displaced water in a hydrophilic micromodel (i.e., drainage), unstable capillary fingering occurred and the pore flow was dominated by successive pore-scale burst events (i.e., Haines jumps). When the same experiment was repeated in a nearly neutral wetting micromodel (i.e., weak imbibition), flow instability and fluctuations were virtually eliminated, leading to a more compact displacement pattern. Energy balance analysis indicates that the conversion efficiency between surface energy and external work is less than 30%, and that kinetic energy is a disproportionately smaller contributor to the energy budget. This is true even during a Haines jump event, which induces velocities typically two orders of magnitude higher than the bulk velocity. These novel measurements further enabled direct observations of the meniscus displacement, revealing a significant alteration of the pore filling mechanisms during drainage and imbibition. While the former typically featured burst events, which often occur only at one of the several throats connecting a pore, the latter is typically dominated by a cooperative filling mechanism involving simultaneous invasion of a pore from multiple throats. This cooperative filling mechanism leads to merging of two interfaces and releases surface energy, causing instantaneous high-speed events that are similar, yet fundamentally different from, burst events. Finally, pore-scale velocity fields were statistically analyzed to provide a quantitative measure of the role of capillary effects in these pore flows.
... Multiphase flow in porous media is related to various natural and industrial processes, such as geological CO2 sequestration (Middleton et al., 2012;Pentland et al., 2011), enhanced oil/gas recovery (Lake, 1989;Orr & Taber, 1984), and groundwater contamination by D(L)NAPL (Dawson & Roberts, 1997;Molnar et al., 2020). When a less viscous fluid invades into the porous media to displace another more viscous one, it always causes interfacial instability and generates different displacement patterns. ...
The flow of multiple immiscible fluids in disordered porous media is important in many natural processes and subsurface applications. The pore-scale disorder affects the fluid invasion pathways significantly and induces the transitions of displacement patterns in porous media. Extensive studies focus on pattern transitions affected by disorder under quasistatic or dynamic conditions, but how the disorder controls the pattern transitions from capillary-dominated regime to viscous-dominated regime is not well understood. Here, we combine microfluidic experiments and theoretical analysis to investigate the role of disorder in fluid displacement. We perform drainage experiments with four different disorders under six flow rate conditions and show that increasing disorder destabilizes displacement fronts for all flow rates considered. Based on the scaling analysis of pore-filling events, we propose a theoretical model that describes the pattern transitions from compact displacement to capillary to viscous fingering as functions of disorder and capillary number. The effects of disorder on both capillary and viscous forces are quantified within the theoretical model. The phase diagram predicted by this model agrees well with our experimental results. We further elucidate the role of disorder in fluid displacement via energy conversion and dissipation. We find that increasing disorder enhances the capillary instabilities and induces more energy dissipated in a capillary-dominated regime, with the dissipation ratio increasing from 28.3% to 56.7%. Our work extends the classic phase diagram to consider the effect of disorder and provides a better understanding of the impact of the disorder on flow behaviors by energy dissipation.
... Drainage is the process by which a nonwetting fluid displaces a wetting fluid from a porous medium. This phenomenon is ubiquitous: it arises in diverse settings including groundwater contamination, oil migration, gas venting from sediments, CO 2 sequestration, mercury porosimetry, soil drying, liquid infusion into porous membranes, and oxygen accumulation within polymer electrolyte membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The ability to accurately predict the displacement pathway of the nonwetting fluid is critically important in all of these cases [3,18]. ...
Capillary fingering is a displacement process that can occur when a nonwetting fluid displaces a wetting fluid from a homogeneous disordered porous medium. Here, we investigate how this process is influenced by a pore size gradient. Using microfluidic experiments and computational pore-network models, we show that the nonwetting fluid displacement behavior depends sensitively on the direction and the magnitude of the gradient. The fluid displacement depends on the competition between a pore size gradient and pore-scale disorder; indeed, a sufficiently large gradient can completely suppress capillary fingering. By analyzing capillary forces at the pore scale, we identify a nondimensional parameter that describes the physics underlying these diverse flow behaviors. Our results thus expand the understanding of flow in complex porous media and suggest a new way to control flow behavior via the introduction of pore size gradients.
... Drainage is the process by which a non-wetting fluid displaces a wetting fluid from a porous medium. This phenomenon is ubiquitous: it arises in diverse settings including groundwater contamination, oil migration, gas venting from sediments, CO 2 sequestration, mercury porosimetry, soil drying, liquid infusion into porous membranes, and oxygen accumulation within polymer electrolyte membranes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The ability to accurately predict the displacement pathway of the non-wetting fluid is critically important in all of these cases [3,18]. ...
Capillary fingering is a displacement process that can occur when a non-wetting fluid displaces a wetting fluid from a homogeneous disordered porous medium. Here, we investigate how this process is influenced by a pore size gradient. Using microfluidic experiments and computational pore-network models, we show that the non-wetting fluid displacement behavior depends sensitively on the direction and the magnitude of the gradient. The fluid displacement depends on the competition between a pore size gradient and pore-scale disorder; indeed, a sufficiently large gradient can completely suppress capillary fingering. By analyzing capillary forces at the pore scale, we identify a non-dimensional parameter that describes the physics underlying these diverse flow behaviors. Our results thus expand the understanding of flow in complex porous media, and suggest a new way to control flow behavior via the introduction of pore size gradients.
... Multiphase flow in porous media exists across innumerable natural and engineering systems, and it plays a defining role in a broad spectrum of applications in the energy and environmental sectors, including enhanced oil recovery (Simjoo et al., 2013), ground water remediation (Dawson & Roberts, 1997), fuel cells (Bazylak, 2009), and carbon capture and storage (CCS; Huppert & Neufeld, 2014). Over the past two decades, geological sequestration of CO 2 in saline aquifers as well as depleted oil and gas reservoirs has attracted significant research attention, as it is widely considered a promising solution for the containment of greenhouse gas effects (Bachu, 2000;Gunter et al., 1997;Koide et al., 1992;Pacala & Socolow, 2004). ...
The pore-scale flow of CO 2 and water in 2-D heterogeneous porous micromodels over a Ca range of nearly three orders of magnitude was explored experimentally. The porous geometry is a close reprint of real sandstone, and the experiments were performed under reservoir-relevant conditions (i.e., 8 MPa and 21 °C), thus ensuring relevance to practical CO 2 operations. High-speed fluorescent microscopy and image processing were employed to achieve temporally and spatially resolved data, providing a unique view of the dynamics underlying this multiphase flow scenario. Under conditions relevant to CO 2 sequestration, final CO 2 saturation was found to decrease and increase logarithmically with Ca within the capillary and viscous-fingering regimes, respectively, with a minimum occurring during regime crossover. Specific interfacial length generally scales linearly with CO 2 saturation, with higher slopes noted at high Ca due to stronger viscous and inertial forces, as supported by direct pore-scale observations. Statistical analysis of the interfacial movements revealed that pore-scale events are controlled by their intrinsic dynamics at low Ca, but overrun by the bulk flow at high Ca. During postfront flow, while permeability is typically correlated with total CO 2 saturation in the porous domain (regardless of its mobility), the saturation of active CO 2 pathways in the current study correlated very well with permeability. This alternate approach to characterize relative permeability could serve to mitigate hysteresis in relative permeability curves. Taken together, these results provide unique insights that address inconsistent observations in the literature and previously unanswered questions about the underlying flow dynamics of this important multiphase flow scenario.
... La stabilité de l'écoulement et la régularité de son front ontétéétudiés lorsqu'ils agissent de manière colinéaire l'unà l'autre ( [Dawson et Roberts, 1997], [Méheust et al., 2002], [Løvoll et al., 2005]), ce qui permet d'évaluer les quantités pertinentes pour prédire le piégeage. En revanche,à l'heure actuelle età notre connaissance, aucuneétude ne s'est spécifiquement focalisée sur la dynamique de la fragmentation de phase induite par la gravité ou par la viscosité. ...
Les milieux poreux sont omniprésents dans le quotidien des hommes du 21ème siècle que ce soit par hasard ou par nécessité. Certains permettent le transport d’une ou plusieurs phases fluides immiscibles, une situation à la fois courante et critique dans de nombreuses applications industrielles. Le transport d’une phase mouillante, l’imbibition, a été largement étudiée mais un certain nombre de problèmes restent ouverts. Dans cette thèse, nous nous sommes concentrés sur trois d’entre eux. La fragmentation de phase induite par la gravité dans une jonction asymétrique a été étudiée. La dynamique et un critère d’apparition ont été prédits analytiquement puis confirmés expérimentalement. Ensuite, l’évolution de l’épaisseur d’un front d’imbibition dans un réseau de capillaires a été simulée numériquement. Les résultats ont permis de lever une controverse de la littérature. Enfin, l’imbibition dans un milieu constitué de lames flexibles déformables a été explorée numériquement et expérimentalement. Il a été montré que la déformabilité des lames induit leur coalescence et agit sur la dynamique de l'imbibition.
... Firstly, the quantity B o sin a ð Þ À C a appears in different wetting problems as the relevant dimensionless number [26]. Secondly, it also appears in the porous media literature for blob mobilization in two-dimensional porous media tilted with an angle a [27,28]. Thirdly, in three-dimensional porous media, all values of a are expected such that the quantity B o À C a , named the generalized Bond number, is used to predict the stability and broadening (if stable) of the two-phase interface [29][30][31]. ...
Hypothesis:
In this study, the spontaneous and forced imbibition of an asymmetric Y junction by a completely wetting fluid submitted to the action of gravity is investigated. The considered junction is made of three capillaries of close but different dimensions. This system is used as a simple model to study gravity induced fluid fragmentation in microfluidic junctions and porous media. Using simple calculations, analytical results predict a fragmentation criterion, two dynamics leading to fluid fragmentation and asymptotically drop lengths and spacings.
Experiments:
Both spontaneous and forced imbibitions of three microfluidic Y junctions were undertaken, varying the capillary and Bond numbers. Results show the validity of the fragmentation criterion, the derived junction imbibition dynamics and confirm qualitatively the analytical description of the fragmentation process.
Findings:
The dynamics prior to fragmentation does not depend on whether the imbibition is forced or spontaneous. However, it depends on the position with respect to gravity of the junction branch of lowest Laplace pressure. Finally, gravity induced fragmentation happens in the squeezing regime described in the Drop-On-Demand (DOD) literature at the junction and is locally controlled by viscosity rather than gravity.
... Negative Bond numbers are generally associated with LNAPLs or with DNAPLs when operated in an upward displacement mode. Results of Dawson and Roberts (1997) show a direct relationship between NAPL saturation and N B since they measured DNAPL saturations through an upward displacement mode. These results are questionable since an upward displacement mode may result in fingering and random variation in residual NAPL saturations. ...
Accidental spills or industrial disposals of elemental mercury (Hg⁰) result in contamination of subsurface soil and groundwater. Hg⁰ is a highly dense non-aqueous fluid whose physico-chemical properties govern its fate and transport in the subsurface. Owing to its liquid state and high density, it percolates down the subsurface by gravity forces and tends to pool when it reaches any impervious barrier. On the other hand, its low solubility and high interfacial tension tend to counteract its downward gravity movement and favour entrapment of a small volume of Hg⁰ in the pore spaces of the subsurface. The trace fraction of entrapped Hg⁰ termed as residual Hg⁰ may bring about severe groundwater contamination due to its chemical and biological transformations to more mobile and more toxic inorganic and organic mercury compounds. It is hypothesized that Hg⁰ behaves as a typical dense non-aqueous liquid and migrates under the influence of capillary, gravity and viscous forces, and eventually gets entrapped in void spaces of the subsurface. The entrapment process and residual Hg⁰ quantification can be described by two-phase capillary pressure water saturation (Pc–Sw) experiments and pore-scale micromodel experiments.
... Due to the application of petroleum products, more and more DNAPLs have come into groundwater system from leakage and other environment accidents. Significantly, most of organic pollutants (POPs) in DNAPLs, such as polycyclic aromatic hydrocarbons (PAHs), Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), are highly toxic, carcinogenic, less easily degraded (Dawson and Roberts, 1997;Hadley and Newell, 2014). As a result, groundwater contamination caused by DNAPL and corresponding risk posed to the environment have attracted widespread attention (Guibeault et al., 2005;Kamon et al., 2004). ...
Representative elementary volume (REV) is important to characterize dense nonaqueous phase liquids (DNAPLs) during surfactant-Enhanced aquifer remediation (SEAR) period. To investigate the REVs of DNAPL in remediation, a perchloroethylene (PCE) SEAR experiment is conducted in a two dimensional (2D) heterogeneous translucent porous media. Light transmission techniques are used to quantify PCE saturation (Soil) and PCE-water interfacial area (AOW). Afterward, corresponding REVs are estimated using a criterion of relative gradient error (εgⁱ) to reveal the change of REVs of DNAPL over the entire remediation period. Results from this work suggest the presence of surface active agents strongly affect the REVs of DNAPL. At the beginning of the SEAR experiment, the frequency of minimum Soil-REV size closely follows a Gaussian distribution in 0.0 mm–11.0 mm. Simultaneously, the frequency of minimum AOW-REV size is close to a Gaussian distribution in 2.0 mm–9.0 mm and appears a peak value in 13.0 mm–14.0 mm. As SEAR experiment proceeds, both the shapes of frequency and cumulative frequency of REV sizes are changed. At the end of SEAR experiment, the frequency of minimum Soil-REV and minimum AOW-REV size tend to Gaussian distributions in 0.0 mm–6.0 mm and 0.0 mm–9.0 mm, respectively, which suggest both minimum Soil-REV size and minimum AOW-REV size show decreasing tendency. Continuous quantification of the REVs of DNAPL is realized in this study to reveal the change of REVs influenced by surface active agent. The finding has important significance on improving our understanding of the characteristics of DNAPL in SEAR process, simulating DNAPL remediation and designing appropriate remediation scheme with high-resolution.
... Immiscible fluid movement is of central importance to diverse natural and engineering processes in the subsurface, including water infiltration through soils, geological carbon sequestration (GCS) [Pachauri et al., 2014;Krevor et al., 2015], enhanced oil/gas recovery [Patzek et al., 2013;Simjoo et al., 2013], and groundwater contamination by nonaqueous liquids [Dawson and Roberts, 1997]. In GCS, injection of CO 2 into deep geological formations displaces native fluid (usually brine) from pore spaces, and brine later flows back to displace scCO 2 when the injection stops. ...
How the wettability of pore surfaces affects supercritical (sc) CO2 capillary trapping in geologic carbon sequestration (GCS) is not well understood, and available evidence appears inconsistent. Using a high-pressure micromodel-microscopy system with image analysis, we studied the impact of wettability on scCO2 capillary trapping during short-term brine flooding (80 seconds, 8 to 667 pore volumes). Experiments on brine displacing scCO2 were conducted at 8.5 MPa and 45°C in water-wet (static contact angle θ = 20° ± 8°) and intermediate-wet (θ = 94° ± 13°) homogeneous micromodels under four different flow rates (capillary number Ca ranging from 9 × 10−6 to 8 × 10−4) with a total of eight conditions (four replicates for each). Brine invasion processes were recorded and statistical analysis was performed for over two thousand images of scCO2 saturations, and scCO2 cluster characteristics. The trapped scCO2 saturation under intermediate-wet conditions is 15% higher than under water-wet conditions under the slowest flow rate (Ca ∼ 9 × 10−6). Based on the visualization and scCO2 cluster analyses, we show that the scCO2 trapping process in our micromodels is governed by bypass trapping that is enhanced by the larger contact angle. Smaller contact angles enhance cooperative pore filling and widen brine fingers (or channels), leading to smaller volumes of scCO2 being bypassed. Increased flow rates suppress this wettability effect.
... Immiscible two-phase fluid flow in porous media is an important process in natural and engineering systems, including water infiltration through soils, geological carbon sequestration Pachauri et al., 2014), enhanced oil/gas recovery (Patzek et al., 2013;Simjoo et al., 2013), and groundwater contamination (Dawson and Roberts, 1997). The non-compact displacement pattern of fluid-fluid interfaces in porous media limits the efficiency of phase displacement. ...
Wettability is an important factor controlling the displacement of immiscible fluids in porous media and therefore affects the flow and transport of supercritical (sc) CO2 in geologic carbon sequestration. Because few studies have focused on the wettability effect in scCO2-brine flow systems, we experimentally and numerically tested influences of wettability on drainage at the pore network scale. Using a high-pressure micromodel-microscopy system, we performed experiments of scCO2 invasion into brine-saturated water-wet and intermediate-wet micromodels, and recorded the scCO2 invasion morphology under reservoir relevant conditions. We also performed pore-scale numerical simulations to infer 3D details of fluid–fluid displacement processes. During drainage under intermediate-wet conditions, we found higher scCO2 saturation, wider scCO2 fingering, and more compact displacement patterns. The simulation results are qualitatively consistent with the experiments. Through quantitative analyses of the experiments, we found that the reduced wettability decreases the displacement front velocity, promotes non-wetting phase pore-filling events in the longitudinal direction, delays the breakthrough time of invading fluid, and increases the displacement efficiency. Simulated results also show that the fluid–fluid interface area follows a unified power-law relation with scCO2 saturation, and show smaller interface area in intermediate-wet case which suppresses the mass transfer between the phases. These pore-scale results provide insights for the wettability effects on CO2–brine immiscible displacement in geologic carbon sequestration.
... A porous media system consisting of 0.4-0.6 mm oil-wet glass beads, soltrol, doped with iodononane, and water, doped with NaBr, was non-destructively imaged using synchrotron X-ray tomography at a resolution of 12.46 Am. The Capillary Number for this particular system, 2.1Â10 À6 , is well below values found in typical groundwater systems and in the range where its value has no impact on the residual nonwetting saturation (e.g., Lake, 1989;Dawson and Roberts, 1997). The physically representative network structure (i.e., geometry and topology) of the system was obtained using techniques developed previously by this group (Al-Raoush et al., 2003;Al-Raoush and Willson, 2005). ...
... Negative Bond numbers are generally associated with LNAPLs or with DNAPLs when operated in an upward displacement mode. Results of Dawson and Roberts (1997) show a direct relationship between NAPL saturation and N B since they measured DNAPL saturations through an upward displacement mode. These results are questionable since an upward displacement mode may result in fingering and random variation in residual NAPL saturations. ...
Elemental mercury (Hg-0) is often found in the vicinity of industrial facilities such as chlor alkali plants, thermometer manufacturing units, and pharmaceutical industries. During accidental land spills or improper disposals of used Hg-0, it penetrates into the subsurface and gets entrapped in the available pore spaces. Once Hg-0 is entrapped in the subsurface as residual blobs, it would be subjected to biochemical transformations and be converted to other toxic forms of mercury. A significant lacuna prevails in addressing Hg-0 contamination and remediation which is dominated by pore scale processes in the subsurface. In this study, a series of experiments was performed to characterize the morphological distribution of Hg-0 at its residual saturation as a function of capillary number (N-C). An initially water-saturated micromodel was flooded with Hg-0 at a prescribed rate to simulate the migration of Hg-0 into the saturated zone. Then Hg-0 was displaced by water flooding and finally residual Hg-0 was established at different N-C. Images taken during the experiment were processed to generate residual Hg-0 saturation, size, shape, and interfacial area. Residual Hg-0 ranged from small spherical blobs to large complex blobs and was found to have an inverse relationship with N-C. The results obtained in this study would serve as fundamental parameters for evaluating relationship amongst residual mercury saturation, interfacial area, and ground water flow in mercury-contaminated sites.
... Under the same conditions of flow rate and surfactant concentration, the 1,2-DCA plume had similar vertical distribution in the two porous media S1 and S2, while the horizontal spreading was farther away in the finer sand S2. The main driving forces of the 1,2-DCA migration were gravity, viscous force and capillary force (Dawson and Roberts, 1997). The horizontal hydraulic force on the DNAPL ganglia was proportional to its sectional area while the vertical gravity was proportional to its volume. ...
During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well.
... While being limited to the immiscible transport of pollutant with water known under the name of DNAPL (Dense Not Aqueous Liquid Phase), these flows meet in the geomaterials ones, the processes of remediation of the grounds, the biofilters employed in waste water treatment, etc… The properties of these flows are complex and often unknown because of a large number of physical parameters. At the present time, the influence of the density, the viscosity or the interfacial tension of DNAPL on its infiltration in the porous medium is studied much by several authors like Pennell and Al, 1996, Dawson and Roberts, 1997, Hofstee et al., 2003, Jeong and Corapcioglu, 2005, Tartakovsky et al.,2007, Meakin et al., 2009. Most of these studies are realized on a macroscopic scale which does not make it possible to understand the retention of small drops of DNAPL in the pores of the medium. ...
... Le nombre adimensionnel utilisé pour la similitude est le nombre de Bond N BO défini par la relation (1). L'écriture du nombre de Bond proposée par Dawson et Roberts (1997) représente le rapport entre les effets de pesanteur et les effets de capillarité dans un milieu poreux. ...
... These flows are complex and often unknown because of the large number of physical parameters involved to describe their properties. At the present time, influence of parameters as density, viscosity or nterfacial tension on the infiltration of NAPL into porous media is much studied by several authors [1][2][3][4][5][6]. Most of these studies are realized at a macroscopic scale. ...
The infiltration with atmospheric pressure of Dense Non Aqueous Phase Liquid (DNAPL) in a model of porous medium saturated by another liquid is studied when this DNAPL liquid has a contact angle characterizing wetting liquid. The model of the porous medium considered consists of an assembly of solid particles for various forms. The influence of the shape of the particles is studied. The results found show the retention capacity of such porous media in function of the shape of the solid particles.
... 또한 TCE가 하부로 이동하면서 투수율이 낮은 지점에서 DNAPL pool을 형성하기도 한다 (Morrison, 2000). 지하수에 유입된 TCE의 이동 및 확산은 매질의 공극률,Dawson and Roberts, 1997). PCE = tetrachloroethylen, TCE = trichlroethylene, TCA = 1,1,1-trichloroethane, cis-DCE = cis-1,2-dichloroethylene, trans-DCE = trans- 1,2-dichloroethylene, CT = carbon tetrachloride, DCM = dichloromethane. ...
This study was performed to summarize application of , and of trichloroethylene (TCE) to studies on environmental forensic field regarding identification of TCE sources and evaluation of contribution of TCE to groundwater using data collected from literatures. , and of TCE give some information regarding sources of TCE because they show specific value according to manufacturing method. Also, TCE do not show a significant isotopic fractionation owing to adsorption and dilution. The isotopic fractionation mainly occurs by biodegradation. In addition, isotopic fractionation factor for TCE is different according to a kind of microorganism participated in biodegradation. However, the isotopic data of TCE have to be applied with chemical compositions of TCE and other hydrogeologic factors because isotopic fractionation of TCE is influenced by various factors.
... A porous media system consisting of 0.4-0.6 mm oil-wet glass beads, soltrol, doped with iodononane, and water, doped with NaBr, was non-destructively imaged using synchrotron X-ray tomography at a resolution of 12.46 Am. The Capillary Number for this particular system, 2.1Â10 À6 , is well below values found in typical groundwater systems and in the range where its value has no impact on the residual nonwetting saturation (e.g., Lake, 1989;Dawson and Roberts, 1997). The physically representative network structure (i.e., geometry and topology) of the system was obtained using techniques developed previously by this group (Al-Raoush et al., 2003;Al-Raoush and Willson, 2005). ...
... Morrow & Songkran (1981) showed that for vertical displacement of a light nonwetting phase (oil) by a denser wetting phase, trapped oil saturation is inversely correlated with N b . However, it was reported that when DNAPL was displaced by a less-dense aqueous phase, the DNAPL saturation increased with N b for upward displacement (Dawson & Roberts 1997). It should be noted that if the downward mobilization of DNAPL is considered, residual saturation decreases with increasing buoyancy force. ...
In this paper, we present a review of seismic-wave propagation in fluid-saturated and partially saturated porous media. Seismic-wave velocity and attenuation are affected by the degree of saturation and the spatial distribution of fluids within the medium. Attenuation mechanisms include local and global flow as well as energy loss caused by scattering. We also present results from acoustic tomography of unconsolidated porous media with residual paraffin saturation. The acoustic attenuation was found to be sensitive to the grain- and subgrain-scale (microscale) distribution of residual saturation; in other words, the residual saturation behaves like soft cement that locally stiffens grain contacts and creates heterogeneity that results in scattering. The effect of microscale phenomena on multigrain scale (macroscale) measurements of seismic-wave attenuation and velocity cannot be ignored.
Description
This unique publication provides a global perspective on one of the most complex issues in hydrology: field and laboratory measurement of low permeability and dual porosity materials. Eleven peer-reviewed papers, written by an international group of experts, focus on the development of techniques to evaluate hydraulic conductivity and remediation of fine grained and dual porosity geologic materials.
It deals with a range of issues related to the measurement of both saturated and unsaturated geologic materials, including:
• Test Procedures
• Laboratory and Field Evaluations
• Low Permeability Environments and Remediation Issues
STP 1415 is a valuable resource for geologists, hydrologists, hydrogeologists, environmental and civil engineers, environmental scientists, waste management personnel, landfill owners and operators, and remediation specialists.
Gravity plays an important role in enhanced oil recovery and groundwater hydrology. A two-dimensional visual homogeneous micromodel was used in this study to describe the role of gravity in displacement processes. A theoretical analysis is proposed for three flow modes, i.e., vertical-upward, vertical-downward, and horizontal displacements, in which water and decane are used for the displacing and the displaced phases, respectively. A relatively compact displacement front was obtained at high flow rates in the three displacement modes, and the front gradually became unstable with a decrease in the flow rate. Compared with horizontal displacement, in vertical-upward displacements, gravity can hinder the evenness of the flow and aggravate the front finger formations at the inlet. This process forces the heavier displacing phase to expand horizontally at the midpoint and weakens the front's fingers. In the vertical-downward displacement process, two states occurred at the same low flow rate: stable flow and unstable flow. Unstable flows occurred more frequently with a decrease in the flow rate. To better understand the role of gravity in displacement, we proposed a theoretical prediction model for the flow state transition of the three displacement modes by combining the capillary force, viscous force, and gravity based on pore-filling events. Finally, to predict the final recovery factor for various displacement modes, four dimensionless formulations were produced using the capillary number, the gravity number, the bond number, and the viscosity ratio.
The remediation of aquifers contaminated by viscous dense non-aqueous phase liquids (DNAPLs) is a challenging problem. Coal tars are the most abundant persistent DNAPLs due to their high viscosity and complexity. Pumping processes leave considerable volume fractions of DNAPLs in the soil and demand high operational costs to reach cleaning objectives. Thermally enhanced recovery focuses on decreasing DNAPL viscosity to reduce residual saturation. The oil industry has previously applied this technique with great success for enhanced oil recovery applications. However, in soil remediation, high porous media permeabilities and product densities may invalidate those techniques. Additionally, the impacts of temperature on coal tar's physical properties have not been thoroughly discussed in available literature. Here, we investigated how coal tar's physical properties, the capillary pressure-saturation curve and the relative permeability of two-phase flow in porous media depend on the temperature and flow rate experimentally. Drainage and imbibition experiments under quasi-static (steady-state) and dynamic (unsteady-state) conditions have been carried out at 293.15 K and 323.15 K in a 1D small cell filled with 1 mm homogeneous glass beads. Two different pairs of immiscible fluids have been investigated, coal tar-water and canola oil-ethanol. Results demonstrated similar trends for temperature effect and values of fluid properties for both liquid pairs, which backs up the use of canola oil-ethanol to model coal tar-water flow. It was found that there is no temperature effect on drainage-imbibition curves or residual saturation under quasi-static conditions. In dynamic conditions, the DNAPL residual saturation decreased by 16 % when the temperature changed from 293.15 K to 323.15 K. This drop was mainly linked to decreasing viscous fingering, as well as the appearance of wetting phase films around the glass beads. Both phenomena have been observed only in dynamic experiments. A high enough pumping flow rate is needed to generate dynamic effects in the porous medium. Ethanol and oil's relative permeabilities also increase with temperature under dynamic measurement conditions. Our findings indicate that flow rate is an important parameter to consider in thermal enhanced recovery processes. These effects are not taken into account in the classically used generalized Darcy's law for modeling two-phase flow in porous media with temperature variation.
A practical design of Non-aqueous phase liquids (NAPLs) remediation strategies requires reliable modeling of interphase mass transfer to predict the retraction of NAPL during processes such as dissolution. In this work, the dissolution process of NAPL during two-phase flow in heterogeneous porous media is studied using pore-network modeling and micromodel experiments. A new physical-experimental approach is proposed to enhance the prediction of the dissolution process during modeling of interphase mass transfer. In this regard, the normalized average resident solute concentration is evaluated for describing the dissolution process at pore-level. To incorporate the effect of medium heterogeneities, a new experimental factor is considered for enhancing corner diffusion modeling. In addition, capillary desaturation curves (CDCs) are predicted during hydraulic flow modeling to estimate initial residual NAPL saturation. The developed network model can predict residual NAPL saturations and mass transfer rate coefficient for a NAPL-water system at different injection rates and fluid saturations. The evaluated mass transfer rate coefficients using the proposed physical-experimental approach show a significant improvement compared to either mechanistic or empirical methods. The proposed approach in this study can be attractive for possible applications in commercial simulators of contaminant transport in porous media.
We present the program package 2HDECAY for the calculation of the partial decay widths and branching ratios of the Higgs bosons of a general CP-conserving 2-Higgs doublet model (2HDM). The tool includes the full electroweak one-loop corrections to all two-body on-shell Higgs decays in the 2HDM that are not loop-induced. It combines them with the state-of-the-art QCD corrections that are already implemented in the program HDECAY. For the renormalization of the electroweak sector an on-shell scheme is implemented for most of the renormalization parameters. Exceptions are the soft-Z2-breaking squared mass scale m122, where an MS¯ condition is applied, as well as the 2HDM mixing angles α and β, for which several different renormalization schemes are implemented. The tool 2HDECAY can be used for phenomenological analyses of the branching ratios of Higgs decays in the 2HDM. Furthermore, the separate output of the electroweak contributions to the tree-level partial decay widths for several different renormalization schemes, computed consistently with an automatic parameter conversion between the different schemes, allows for an efficient analysis of the impact of the electroweak corrections and the remaining theoretical error due to missing higher-order corrections. The latest version of the program package 2HDECAY can be downloaded from the URL https://github.com/marcel-krause/2HDECAY.
Program summary
Program Title: 2HDECAY
Program Files doi: http://dx.doi.org/10.17632/znthhmjg7r.1
Licensing provisions: GPLv3
Programming language: FORTRAN 77/90; Python 2/3
Nature of problem: Numerical calculation of branching ratios and partial decay widths for the decays of all Higgs bosons in the Two-Higgs-Doublet Model at electroweak one-loop level for non-loop-induced on-shell decays in combination with contributions from the state-of-the-art QCD corrections and off-shell decays already implemented in HDECAY 6.52. Renormalization of the electroweak sector in 17 different renormalization schemes and automatic input parameter conversion for the comparison of numerical results calculated within these different schemes.
Solution method: All tree-level and one-loop contributions to the genuine decay amplitudes and for the definition of the renormalization constants are calculated fully analytically and evaluated numerically. The electroweak corrections are consistently combined with the existing corrections implemented in HDECAY 6.52.
Additional comments including restrictions and unusual features: For the electroweak corrections, only non-loop-induced on-shell decays are implemented.
Immiscible displacement in porous media is common in many practical applications. Under quasi-static conditions, the process is significantly affected by disorder of the porous media and the wettability of the pore surface. Previous studies have focused on wettability effects, but the impact of the interplay between disorder and contact angle is not well understood. Here, we combine microfluidic experiments and pore-scale simulations with theoretical analysis to study the impact of disorder on the quasi-static displacement from weak imbibition to strong drainage. We define the probability of overlap to link the menisci advancements to displacement patterns, and derive a theoretical model to describe the lower and upper bounds of the cross-over zone between compact displacement and capillary fingering for porous media with arbitrary flow geometry at a given disorder. The phase diagram predicted by the theoretical model shows that the cross-over zone, in terms of contact angle range, expands as the disorder increases. The diagram further identifies four zones to elucidate that the impact of disorder depends on wettability. In zone I, increasing disorder destabilizes the patterns, and in zone II, a stabilizing effect plays a role, which is less significant than that in zone I. In the other two zones, invasion morphologies are compact and fingering, respectively, independent of both contact angle and disorder. We evaluate the proposed diagram using pore-scale simulations, experiments in this work and in the literature, confirming that the diagram can capture the effect of disorder on displacement under different wetting conditions. Our work extends the classical phase diagrams and is also of practical significance for engineering applications.
This paper describes some properties of the Fe-based materials infiltrated with tin bronze and Cu-based materials infiltrated with tin. It was shown that due to the increased thermal conductivity infiltrated materials based on iron and copper have high tribotechnical properties. With an increase the thermal conductivity the coefficient of friction is reduced, and the seizure pressure increases in infiltrated iron-based materials as a result of the increase in the copper phase and certainty of its morphology, and in copper materials through the creation of a gradient structure in content of tin.
In this study, biological PCE degradation by using a BTEX degrading bacterium, named BJ10, under aerobic conditions in the presence of toluene was examined. According to morphological, physiological characteristics, 16S rDNA sequencing and fatty acid analysis, BJ10 was classified as Pseudomonas putida. As a result of biological PCE degradation at low PCE concentrations (5 mg/L), PCE removal efficiency by P. putida BJ10 was 52.8% for 10 days, and PCE removal rate was 5.9 nmol/hr (toluene concentration 50 mg/L, initial cell density 1.0 g (wet weight)/L, temperature 30, pH 7 and DO 3.0-4.2 mg/L . At high PCE concentration (100 mg/L), PCE removal efficiency by P. putida BJ10 was 20.3% for 10 days, and PCE removal rate was 46.0 nmol/hr under the same conditions. The effects of various toluene concentration (5, 25, 50, 100, 200 mg/L) on PCE degradation were examined under the same incubation conditions. The highest PCE removal efficiency of PCE was 57.0% in the initial PCE concentration of 10 mg/L in the presence of 200 mg/L toluene for 10 days. Furthermore, the additional injection of 5.5 mg/L PCE (total 7.6 mg/L) made 63.0% degradation for 8 days in the presence of 50 mg/L toluene under the same conditions. Its removal rate was 13.5 nmol/hr, which was better than the initial removal rate (8.1 nmol/hr).
We study the problem of the transformation of a given reactant species into
an immiscible product species, as they flow through a chemically active porous
medium. We derive the equation governing the evolution of the volume fraction
of the species -- in a one-dimensional macroscopic description --, identify the
relevant dimensionless numbers, and provide simple models for capillary
pressure and relative permeabilities, which are quantities of crucial
importance when tackling multiphase flows in porous media. We set the domain of
validity of our models and discuss the importance of viscous coupling terms in
the extended Darcy's law. We investigate numerically the steady regime and
demonstrate that the spatial transformation rate of the species along the
reactor is non-monotonous, as testified by the existence of an inflection point
in the volume fraction profiles. We obtain the scaling of the location of this
inflection point with the dimensionless lengths of the problem. Eventually, we
provide key elements for optimization of the reactor.
BACKGROUND
Most experts acknowledge that low aqueous solubility results in low mass recovery rates using pump-and-treat (P&T), making such systems ineffective for coal tar (a multi-component NAPL) recovery. It is proposed to increase the apparent aqueous solubility of coal tar by orders of magnitude as an enhancement to conventional P&T schemes (or ‘P&T–E’), increasing coal tar recovery rates, reducing the pore volumes and time required for complete recovery, thus translating into cost savings. RESULTSBatch test results of aqueous solutions containing anionic surfactant, co-solvent, and electrolyte are presented that were studied for both compatibility with a field-obtained coal tar and effectiveness at solubilizing the coal tar above its aqueous solubility. Seven surfactants were tested at room temperature (23C) in aqueous solutions containing the surfactant with co-solvents and electrolytes. The most promising surfactant solution solubilized upwards of 40 000 mg L−1 coal tar. A 1–D column test resulted in 97% recovery using the promising surfactant. CONCLUSIONSP&T–E could significantly increase coal tar solubility without causing the formation of a rate-limiting, solid-like film and offers a promising approach for the remediation of coal tar from the subsurface. © 2013 Society of Chemical Industry
This paper presents an experimental study on mixed soil contamination, more specifically on heavy metal behaviour in soil contaminated by residual non-aqueous phase liquids (NAPLs). Remediation of mixed contaminated sites is a complex technical goal because of the presence of physically and chemically different contaminants and potential interactions between them. Commonly encountered contaminants in mixed contaminated soils include light and dense organic liquids (LNAPLs, DNAPLs) and heavy metals. This study investigated interactions between three residual LNAPLs and three heavy metals (Cd, Cu, Pb) in a carbonated soil. The objectives of the study were to (i) establish the presence of interactive processes in the behaviour of the contaminants, with a focus on the influence of residual LNAPL on heavy metal transport and retention; and (ii) determine the nature of these interactions. Results showed that the LNAPL having the highest residual saturation enhanced heavy metal mobility and decreased heavy metal retention by the soil. On the other hand, the geochemical distribution of heavy metals was not significantly modified by chemical interactions with the residual LNAPLs. Specific modifications of Pb and Cu geochemical distributions rather appeared to be the result of modifications of soil hydrodynamics by residual LNAPL.
Non-aqueous phase liquids (NAPLs) like petroleum hydrocarbons and chlorinated solvents have resulted in contamination of soils and ground water, which aroused widespread concern. It's quite important to delineate pollution area for remediation according to different soil types with pollutants properties in consideration. In this paper, a two-dimension visual sand box apparatus was constructed, with four typical NAPLs selected for infiltration experiments conducted in initially dry porous media. The main driving force was identified and fingering patterns were compared. The fractal dimension was used to give quantitative description. The present work indicates that the main driving force was capillary forces and the mechanism was the capillary fingering. The fingers varied from skeletal patterns to fleshy patterns and the infiltration area increased when the capillary number and the bond number decreased for NAPLs with the same level of viscosity. The high viscous force resulted in larger finger width and infiltration area. The same change between fluids happened in finer media. Fractal dimensions were positively correlated with the finger width and infiltration area, which is helpful in the pollution area characterization.
La finalité de ce travail est de comprendre le comportement et le devenir des polluants urbains entraînés par l’eau de ruissellement sur les sols comme les chaussées urbaines. Ainsi, des expériences de visualisation en laboratoire et des simulations numériques sont conduites pour illustrer et analyser l’infiltration de l’eau chargée en particules fluides non-miscibles ou en particules solides dans des milieux poreux indéformables. Les résultats obtenus contribuent du point de vue fondamental à la connaissance à l’échelle microstructurale des écoulements polyphasiques dans les milieux poreux en prenant en compte le caractère mouillant ou non mouillant des fluides. Du point de vue appliqué, les résultats présentés contribuent à la connaissance des mécanismes de rétention et de colmatage dans les matériaux poreux urbains tels que les chaussées drainantes ou les tranchées filtrantes.Visualization experiments and CFD simulations are used to illustrate and analyze the infiltration of water charged with Non Aqueous Phase Liquid (NAPL) or solid particles in a static porous medium Using visualizations across transparent materials, the analyses focus on the retention mechanisms and the clogging mechanisms in porous materials at microstructural scale. The objective of this work is to investigate the behavior of urban pollutant particles driven by surface runoff water inside urban soil, and urban roadways.
Predicting the dissolution rate of nonaqueous phase liquids (NAPLs) in groundwater is difficult, as the effects of variable pore and NAPL blob geometry are poorly understood. To elucidate these effects, fluorescence microscopy and digital image analysis were used to quantify the size and location of variably distributed NAPL blobs during dissolution in homogeneous and heterogeneous pore networks etched into silicon wafers. Results show that the dissolution rate constant (expressed as the Sherwood number, Sh) is relatively constant regardless of pore and NAPL blob geometry when the average mass transfer length scale remains constant during dissolution. Results also show that Sh increases with Peclet (Pe) between 2 and 26 and then levels off. The limiting value of Sh reached depends on the average diffusion length scale; this length scale was directly calculated and found to vary depending on the pore and NAPL blob geometry. For example, the average diffusion length scale decreases (and Sh increases) as the pore throat width to grain diameter increases. Last, results show that the volumetric NAPL content (thetan) is linearly related to the specific NAPL-water interfacial area (ait) over much of the dissolution process. However, this relationship depends on the pore and blob size distribution. For example, when multipore blobs control dissolution, the relationship between these parameters will change as smaller blobs dominate dissolution at low thetan. These results are important because existing mass transfer correlations do not account for limiting values of Sh that can be obtained at high Pe for the effect of blob or pore geometry on the average diffusion length scale (and therefore on Sh) or for the effect of pore geometry and transient blob size distribution on the relationship between ait and thetan.
Perchloroethylene (PCE) was injected into fractured limestone samples (approximately 0.3 m × 0.3 m square) under controlled conditions to assess nonwetting phase fracture retention capacity. Testing was performed using two rock samples containing a single fracture in each, one fractured along a bedding plane and the other fractured along a prominent stylolitic joint. Residual PCE saturation decreased from 21% of the fracture volume at horizontal to 3% at completely vertical in the bedding plane fracture and decreased from 27% to 10% of the fracture volume under the same conditions in the stylolitic fracture. A portion of the retained residual was removed by waterflooding the fractures. The PCE retention capacity of both fractures exhibited a strong correlation with combined capillary and Bond number (Nc + krWNB) provided that initial residual saturation was defined in the absence of both buoyant and viscous forces. Residual PCE saturation decreased as the magnitude of NC + krWNB increased; however, even at Nc + krWNB values approaching 10−2, all residual PCE was not completely removed from the fractures.
The entrapment of nonwetting phase fluids in unconsolidated porous media systems is strongly dependent on the pore-scale geometry and topology. Synchrotron X-ray tomography allows us to nondestructively obtain high-resolution (on the order of 1-10 micron), three-dimensional images of multiphase porous media systems. Over the past year, a number of multiphase porous media systems have been imaged using the synchrotron X-ray tomography station at the GeoSoilEnviroCARS beamline at the Advanced Photon Source. For each of these systems, we are able to: (1) obtain the physically-representative network structure of the void space including the pore body and throat distribution, coordination number, and aspect ratio; (2) characterize the individual nonwetting phase blobs/ganglia (e.g., volume, sphericity, orientation, surface area); and (3) correlate the porous media and fluid properties. The images, data, and network structure obtained from these experiments provide us with a better understanding of the processes and phenomena associated with the entrapment of nonwetting phase fluids. Results from these experiments will also be extremely useful for researchers interested in interphase mass transfer and those utilizing network models to study the flow of multiphase fluids in porous media systems.
The long-term behavior of five organic solutes during transport over a period of 2 years in ground water under natural gradient conditions was characterized quantitatively by means of moment estimates. Total mass was conserved for two of the organic compounds, carbon tetrachloride and tetrachloroethylene, while the total mass declined for three other compounds, bromoform, 1,2-dichlorobenzene, and hexachloroethane. The declines in mass for the latter three compounds are interpreted as evidence of transformation of the compounds. Retardation factors for the organic solutes, relative to chloride, ranged from 1.5 to 9.0, being generally greater for the more strongly hydrophobic compounds. The retardation is attributed to sorption. The apparent retardation factor increased markedly for all compounds over the duration of the experiment, by as much as 150%. Results from temporal and spatial sampling were in good agreement when compared at the same scale of time and distance.
Groundwater contamination by nonaqueous liquids such as organic solvents and petroleum hydrocarbons frequently occurs as a result of surface spills, tank leaks, and improper disposal practices. This first of two papers examines the physics governing the emplacement and movement of a separate phase in porous media, the role of sorption, and the conditions necessary to mobilize a separate phase. The movement of the separate phase is controlled by capillary forces, and ganglia displacement by groundwater is not possible under reasonable hydraulic gradients. In addition, because of mass transfer limitations in liquid phase dissolution, groundwater extraction at contaminated sites is shown to be ineffective in removing the nonaqueous contaminant within a reasonable time frame. Therefore other means of mobilizing the trapped second phase are needed, steam displacement is proposed and steam front propagation through contaminated porous media is evaluated. The results of laboratory experiments supporting some of these analytical results are presented in the second paper (Hunt et al., this issue).
A large-scale field experiment on natural gradient transport of solutes in groundwater has been conducted at a site in Borden, Ontario. Well-defined initial conditions were achieved by the pulse injection of 12 m3 of a uniform solution containing known masses of two inorganic tracers (chloride and bromide) and five halogenated organic chemicals (bromoform, carbon tetrachloride, tetrachloroethylene, 1,2-dichlorobenzene, and hexachloroethane). A dense, three-dimensional array of over 5000 sampling points was installed throughout the zone traversed by the solutes. Over 19,900 samples have been collected over a 3-year period. The tracers followed a linear horizontal trajectory at an approximately constant velocity, both of which compare well with expectations based on water table contours and estimates of hydraulic head gradient, porosity, and hydraulic conductivity. The vertical displacement over the duration of the experiment was small. Spreading was much more pronounced in the horizontal longitudinal than in the horizontal transverse direction; vertical spreading was very small. The organic solutes were retarded in mobility, as expected.
Waterflooding is an important method of improving recovery, but successful waterflood performance requires a sound design. Waterflooding begins with understanding the basic principles of immiscible displacement, then presents a systematic procedure for designing a waterflood. The emphasis is on fundamental concepts and their application in solving various waterflooding problems. Design procedures that can be prepared as small computer programs and selected computer subprograms for more complex designs are presented.
A simplified nonwetting liquid entrapment model for three fluid phase porous media is presented. The model requires one additional parameter in the constitutive relationship, effective residual oil saturation, and can be implemented in a numerical multiphase flow model. The validity of the model was verified with good agreement between the predicted and observed saturations. The laboratory column experiment which showed percentage of trapped oil volume under a given set of boundary conditions is very sensitive and varies in a highly nonlinear manner with the effective residual oil saturation. -Authors
In systemizing fluids potentially harmful to groundwater with regard to their migration behaviour, it has been proven useful in groundwater hydrology to divide these into two main groups $$\text{miscrible}\,\text{with}\,\text{water - immiscible}\,\text{with}\,\text{water}$$ based on fluid dynamics. This division is indispensable since the simultaneous flow of two (or more) immiscible fluids gives a completely different migration pattern than that of the simultaneous flow of fluids miscible with one another. Accordingly, one must fundamentally differentiate between the two types of flow $$\text{one phase flow - two (multi - ) phase flow}\text{.}
The trapping of residual nonwetting phase in packings of equal spheres has been investigated for a wide range of capillary numbers, vμ/σ (ratio of viscous to capillary forces) and Bond numbers, ΔpgR2/σ (ratio of gravity to capillary forces). For vertical displacement, residual saturations varied from normal values of about 14.3% when the Bond number was less than 0.00667 and the capillary number was less than 3 × 10−6, down to near zero when either the Bond number exceeded 0.35 or the capillary number exceeded about 7 × 10−4. Precise correlation of residual saturation with a linear combination of Bond and capillary numbers showed that the effects of gravity and viscous forces on trapping are superposed. The equivalence of gravity and viscosity forces is used to determine relative permeability of the displacing fluid at the flood front. Relative permeabilities to the wetting phase behind the flood front at less than normal residual saturations are reported. For displacement at various dip angles, the effect of gravity is greater than that predicted by using results for vertical displacement with the Bond number resolved according to angle of dip.
This text covers all forms of enhanced oil recovery techniques with both fundamental principles and specialized applications. Students in all areas of fluid flow in permeable media and professional researchers can benefit from the unified approach to EOR based on common first principles, conservation of mass, momentum, and energy. Mathematical techniques based on phase behavior and the method of characteristics (MOC) are fundamental to the text.
This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., April 22–24, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
Abstract
An "alternate path" theory is presented which quantitatively relates residual oil saturation to petrophysical properties over a broad range of varying interfacial and viscous conditions. The model allows for intermediate water wetting up to 90 degrees, and discontinuous trapped oil in single, or in interconnected pores. Basic petrophysical measurements, pores. Basic petrophysical measurements, including capillary pressure and relative permeabilities, provide functions related to permeabilities, provide functions related to microscopic pore dimensions. These functions are used to develop a relationship between trapped oil saturation and the displacement conditions of pressure gradient and interfacial tension.
Introduction
Determination of residual oil saturation has been the subject of a great quantity of experimental and some theoretical research for a number of years. Initially, knowledge of residual oil was needed principally for reservoir volumetric calculations in the determination of primary or waterflood recovery. With the advent of tertiary recovery methods, more accurate determination of the remaining oil saturation has become necessary for evaluation of processes which are initiated at low oil saturations. Finally, in the specific tertiary processes which alter interfacial tension or wettability, the conditions necessary for effective process design require an even more thorough understanding of the mechanisms that control release of residual oil.
Because of the complexity of the subject and the wide range of conditions found in various oil fields, a complete treatment of residual oil saturation is not possible. Individual aspects of the problem, including fluid properties, wettability, capillary pressures, and relative permeability have been pressures, and relative permeability have been extensively studied. Fluid properties such as density and viscosity are almost always precisely known. Interfacial tension is not precisely known. Interfacial tension is not as well defined, partly because of its lesser utility in reservoir calculations, and partly because of its greater sensitivity to change with pressure, temperature or minor contaminants. Methods of quantifying wettability have been developed which permit categorization of reservoirs in a fairly precise manner and these results provide insight into imbibition rates and relative permeability. In addition, capillary pressure methods have been used for calculation of pore size distribution and equilibrium oil saturation.
The three-dimensional movement of a tracer plume containing bromide and chloride is investigated using the data base from a large-scale natural gradient field experiment on groundwater solute transport. The analysis focuses on the zeroth-, first-, and second-order spatial moments of the concentration distribution. These moments define integrated measures of the dissolved mass, mean solute velocity, and dispersion of the plume. Moments are estimated from the point observations using quadrature approximations tailored to the density of the sampling network. The estimators appear to be robust, with acceptable sampling variability. Estimates of the mass in solution for both bromide and chloride demonstrate that the tracers behaved conservatively, as expected. Analysis of the first-order moment estimates indicates that the experimental tracer plumes traveled along identical trajectories. The horizontal trajectory is linear and aligned with the hydraulic gradient. The vertical trajectory is curvilinear, concave upward. The total vertical displacement is small, however, so that the vertical component of the mean solute velocity vector is negligible. The estimated mean solute velocity is identical for both tracers (0. 091 m/day) and is spatially and temporally uniform for the first 647 days of travel time.
The spatial variability of hydraulic conductivity at the site of a long-term tracer test performed in the Borden aquifer was examined in great detail by conducting permeability measurements on a series of cores taken along two cross sections, one along and the other transverse to the mean flow direction. Along the two cross sections, a regular-spaced grid of hydraulic conductivity data with 0.05 m vertical and 1.0 m horizontal spatial discretization revealed that the aquifer is comprised of numerous thin, discontinuous lenses of contrasting hydraulic conductivity. Estimation of the three-dimensional covariance structure of the aquifer from the log-transformed data indicates that an exponential covariance model with a variance equal to 0.29, an isotropic horizontal correlation length equal to about 2.8 m, and a vertical correlation length equal to 0.12 m is representative. A value for the longitudinal macrodispersivity calculated from these statistical parameters using three-dimensional stochastic transport theory developed by L. W. Gelhar and C. L. Axness (1983) is about 0.6 m. For the vertically averaged case, the two-dimensional theory developed by G. Dagan (1982, 1984) yields a longitudinal djspersivity equal to 0.45 m. Use of the estimated statistical parameters describing the ln (K) variability in Dagan's transient equations closely predicted the observed longitudinal and horizontal transverse spread of the tracer with time. Weak vertical and horizontal dispersion that is controlled essentially by local-scale dispersion was obtained from the analysis. Because the dispersion predicted independently from the statistical description of the Borden aquifer is consistent with the spread of the injected tracer, it is felt that the theory holds promise for providing meaningful estimates of effective transport parameters in other complex-structured aquifers.
The wettability of a core will strongly affect its waterflood behavior and relative permeability because wettability is a major factor controlling the location, flow, and distribution of fluids in a porous medium. When a strongly water-wet system is waterflooded, recovery at water breakthrough is high, with little additional oil production after breakthrough. Conversely, water breakthrough occurs much earlier in strongly oil-wet systems, with most of the oil recovered during a long period of simultaneous oil and water production. Waterfloods are less efficient in oil-wet systems compared with water-wet ones because more water must be injected to recover a given amount of oil.
This paper examines the effects of wettability on waterflooding, including the effects on the breakthrough and residual oil saturations (ROS's) and the changes in waterflood behavior caused by core cleaning. Also covered are waterfloods in heterogeneously wetted systems. Waterfloods in fractionally wetted sandpacks, where the size of the individual water-wet and oil-wet surfaces are on the order of a single pore, behave like waterfloods in uniformly wetted systems. In a mixed-wettability system, the continuous oil-wet paths in the larger pores alter the relative permeability curves and allow the system to be waterflooded to a very low ROS after the injection of many PV's of water.
Introduction
This paper is the sixth in a series of literature surveys covering the effects of wettability on core analysis. Wettability has been shown to affect waterflood behavior, relative permeability, capillary pressure, irreducible water saturation (IWS), ROS, dispersion, simulated tertiary recovery, and electrical properties. Earlier but less complete reviews covering the effects of wettability on waterflooding and relative permeability can be found in Refs. 6 through 17.
Waterflooding is a frequently used secondary recovery method in which water is injected into the reservoir, displacing the oil in front of it. Assuming that the reservoir is initially at IWS, only oil is produced until breakthrough, the time when water first appears at the production well. After breakthrough, increasing amounts of water and decreasing amounts of oil are produced. The process continues until the WOR is so high that the well becomes uneconomical to produce.
Waterfloods in water-wet and oil-wet systems have long been known to behave very differently. For uniformly wetted systems, it is generally recognized that a water-flood in a water-wet reservoir is more efficient than one in an oil-wet reservoir. An example of the effect of wettability on waterflood performance calculations is shown in Fig. 1. Steady-state oil/water relative permeabilities were measured in an outcrop Torpedo sandstone using a mild NaCl brine and a 1.7-cp [ 1.7-mPa-s] refined mineral oil. The wettability of the system was controlled by adding either (1) various amounts of barium dinonyl naphthalene sulfonate to the oil, which made the system more oil-wet, or (2) Orvus K TM liquid (a detergent) to the brine to achieve a strongly water-wet system with a contact angle of O degrees through the brine. Wettability was monitored by contact-angle measurements on a quartz crystal. The measured relative permeability curves were used to calculate field performance, assuming a single 20-acre [8-ha] five-spot with homogeneous properties. Oil and water viscosities were assumed to be 1.74 and 0.35 cp [1.74 and 0.35 mPa-s], respectively. The calculated waterflood results are shown in Fig. 1, where water breakthrough is the point at which each curve first becomes nonlinear. Fig. 1 demonstrates that earlier water break-through and less efficient oil recovery occur as the system becomes more oil-wet. For example, 8 % less oil will be produced at a WOR of 25 if the contact angle is 138 degrees [2.4 rad], rather than 47 degrees [0.82 rad].
Waterflood recovery is controlled by the oil and water relative permeabilities of a system and by the water/oil viscosity ratio. In laboratory-scale experiments, inlet and outlet end effects can also affect the recovery. The effects of relative permeabilities and viscosity ratio on waterflooding are demonstrated by the fractional flow equation. If we neglect capillary effects and assume a horizontal system, the simplified form of the fractional flow equation (e.g., see Craig) is
(1)
where
fw = fractional flow of water, Sw = water saturation, = oil and water viscosities, respectively, cp, and = oil and water relative permeabilities, respectively.
Eq. 1 shows that the fractional flow of water at a given saturation is increased when the water/oil viscosity ratio is decreased. Decreasing the water/oil viscosity ratio will cause earlier breakthrough and less efficient oil production. Similar effects will occur when the water/oil relative permeability ratio is increased. The oil and water relative permeabilities are explicit functions of the water saturation. They are also affected by pore geometry, wettability, fluid distribution, and saturation history.
Water-Wet Systems. As discussed by Anderson, wettability has a strong effect on relative permeability. As the core becomes more oil-wet, the water relative permeability increases and the oil relative permeability decreases. The water will flow more easily in com-parison with the oil during a waterflood, causing progressivelearlier breakthrough and less efficient recovery. Wettability affects relative permeability and waterflood behavior because it is a major factor controlling the location, flow and spatial distribution of fluids in the core. Craigs and Raza et al. have given good summaries of the effects of wettability on the distribution of oil and water in a core. Consider a strongly water-wet rock initially at the IWS. Water, the wetting phase, will occupy the small pores and form a thin film over all the rock surfaces. Oil, the nonwetting phase, will occupy the centers of the larger Pores. This fluid distribution occurs because it is most energetically favorable. Any oil placed in the small pores would be displaced into the center of the large pores by spontaneous water imbibition, because this would lower the energy of the system.
JPT
P. 1605
Knowledge of the theory underlying the behavior of mixtures of fluids inreservoir rocks is essential to the proper solution of certain types ofproblems in petroleum production, but is as yet incompletely developed. Theobject of this paper is to show the application of well establishedthermodynamic and physical principles to these problems, and thus to assist inthe development of the basic theory. For convenience the problems to beconsidered here may be divided into two groups:
1. Static problems, involving only the static balance between capillary forcesand those due to the difference in densities of the fluids; i.e., gravitationalforces.
2. Dynamic problems, involving analysis of the motion of mixtures of immisciblefluids in porous media under the influence of forces due to gravity,capillarity, and an impressed external pressure differential.
Capillary Equilibrium in Sands
Under this heading the static type of problem will be discussed and the resultsof experimental investigations on the capillary properties of unconsolidatedsands will be presented. Although the discussion of this section is, in asense, prefatory to the treatment of problems of mixture flow, the conceptsdeveloped here have considerable intrinsic importance apart from theirapplication to flow problems. For, it is reasonable to postulate that thereservoir fluids are, owing to their long existence in undisturbed mutualcontact prior to exploitation, in substantial equilibrium. It follows thattheir distribution in the reservoir at the time of tapping should be entirelypredictable from the theory of capillary equilibrium, provided certainexperimentally measurable properties of the reservoir rock are known. Knowledgeof the distribution of the several fluids in the reservoir is, of course,helpful in the estimation of reserve, and in other problems.
It is to be emphasized that throughout the discussion of capillary statics itis assumed that the fluids are in equilibrium from the capillary standpoint.Thus, water, where it is referred to as being in a reservoir, will beunderstood to be interstitial water, present at the time of drilling thereservoir, commonly termed "connate" water.
The theory developed here is perfectly general for any porous solid, whether acarefully prepared unconsolidated sand or a natural sandstone from an oilreservoir. At present, however, only problems involving clean, unconsolidatedsands can be made to yield numerical solutions, since only such sands have beenadequately investigated experimentally. Experimental evaluation of thepertinent properties of natural reservoir rocks will permit the extension ofthe numerical treatment to problems involving these materials. We shall nowconsider in some detail the static equilibrium of fluid mixtures in poroussolids; that is, the manner in which the reservoir fluids are distributedvertically when the forces due to capillarity are just balanced by those due togravitation.
T.P. 1223
Phase behavior, interfacial tension (IFT), viscosity, and density data were determined for the system 2% CaCl2 brine/isopropyl alcohol (IPA)/isooctane. Liquid pairs from this system were used in a test of capillary number as a correlating function for mobilization of residual oil in geometrically similar porous media as provided by bead packs. Close correlation of results was obtained for a more than five-fold variation in permeability and a more than six-fold variation in IFT. Extensive investigation was also made of the change in trapped oil saturation given by vertical upward flooding; the ratio of gravity to capillary forces varied more than 100-fold. A correlation between trapped oil saturation and Bond number was obtained that was in good agreement with previous results obtained for gas entrapment. However, capillary numbers for entrapment of a given reduced residual oil saturation (ROS) were found to be slightly higher than those for entrapment of gas.
Relative permeabilities were independent of whether the trapped phase was oil or gas and were determined mainly by the magnitude of the trapped nonwetting-phase saturation.
Capillary numbers for mobilization of residual oil from bead packs were much higher than typical values for sandstones. For bead packs that had been consolidated by sintering, capillary numbers for prevention of entrapment increased and those for mobilization decreased. The net result was that differences in capillary numbers for mobilization and entrapment were greatly reduced and results became more akin to relationships observed for consolidated sandstones.
Quantitative descriptions of two-phase flow in the subsurface require knowledge of the capillary pressure-saturation relationships. The effect of interfacial forces on the drainage capillary pressure-saturation relationship for organic liquid-water systems is usually expressed by the ratio of the liquid-liquid interfacial tensions as given by Leverett's (1941) function. To assess the appropriateness of this approach for primary drainage of organic liquid-water systems typical of hazardous waste sites and to evaluate its extendability to spontaneous imbibition, measurements were made of these relationships for various immiscible liquid systems in unconsolidated sand. The results showed increasing deviations with decreasing interfacial forces between the measured values and those predicted by a ratio of interfacial tensions. To improve the predictive capability of Leverett's function, forms including the intrinsic contact angle and roughness were examined. Scaling of the capillary pressure relationships was best achieved by including a correction for both interface curvature and roughness. These corrections became significant for drainage for contact angles larger than 35°–55°, and for imbibition for contact angles larger than 15°–25°. None of the forms of Leverett's function examined predicted the increased residual saturation with decreasing interfacial forces observed in this study. Consequently, their ability to scale the measured data was predicated on posing the saturation of the wetting phase in terms of the variable effective saturation.
Concepts for rate limitation of sorptive uptake of hydrophobic organic solutes by aquifer solids are reviewed, emphasizing physical diffusion models and in the context of effects on contaminant transport. Data for the sorption of tetrachloroethene (PCE) and 1,2,4,5-tetrachlorobenzene (TeCB) on Borden sand are presented, showing that equilibrium is attained very slowly, requiring equilibration times on the order of tens of days for PCE and hundreds of days for TeCB. The rate of approach to equilibrium decreased with increasing particle size and sorption distribution coefficient, in accordance with retarded intragranular diffusion models. Pulverization of the samples significantly decreased the required time to equilibrium without changing the sorption capacity of the solids. Batch sorption methodology was refined to allow accurate measurement of long-term distribution coefficients, using purified {sup 14}C-labelled solute spikes and sealed glass ampules. Sorption isotherms for PCE and TeCB were conducted with size fractions of Borden sand over four to five orders of magnitude in aqueous concentration, and were found to be slightly nonlinear (Freundlich exponent = 0.8). A concentrated set of data in the low concentration range (
The objective of this research was to examine the influence of capillary forces on two-phase liquid flow in groundwater. This objective was accomplished by investigating interfacial tension, contact angle, capillary pressure, and relative permeability for systems representative of contaminated aquifers. The interfacial tensions of six compounds, benzaldehyde, bromobenzene, n-dodecane, tetrachloroethylene, 1,1,2-trichloroethane, and o-xylene, were measured using the pendant drop method. The contact angles for these six compounds were measured on five solid surfaces: Teflon, glass, steel, calcite, and albite. Drainage and imbibition capillary pressure relationships were measured for four organic compound-water systems in an unconsolidated sand. Drainage and imbibition relative permeabilities were measured at groundwater velocities for three organic compound-water systems in the same sand.
Organic liquids that are essentially immiscible with water migrate through the subsurface through the influence of capillary, viscous and buoyancy forces. Four experimental methods were employed. First, quantitative displacement experiments using short soil columns; second, additional quantitative displacement experiments using long soil columns; third, pore and blob casts; and fourth, etched glass micromodels were used to visually observe dynamic multi-phase displacement processes in pore networks. It was found that the spatial distribution and saturation of organic liquid within the porous media depends on a variety of factors, including: (1) the fluid properties of interfacial tension, viscosity, and density; (2) soil structure and heterogeneity; (3) the number of fluid phases present; and (4) the fluid flow rates. Photomicrographs on a pore scale show that the residual organic liquid appears as blobs, films, rings, and wedges of microscopic size. The size, shape, and spatial distribution of these blobs, films, rings, and wedges affects the dissolution of organic liquid into the water phase, volatilization into the air phase, and the adsorption and biodegradation of organic components. These four processes are of concern in the prediction of pollution migration and the design of aquifer remediation schemes.
The purpose of this paper is to explore reasons for the observed difficulty of groundswater cleanup and note some implications that become clear during this process. Tthe discussion is limited to organic contaminants because they are the most health-threatening chemicals detected in groundwater and because the greatest difficulties in groundwater remediation have been encountered at organic contamination sites.
Percolation theory of transport in random composites is used to explain the correlation between the residual saturation of nonwetting phase in porous media after displacement by a wetting phase and the capillary number, this number being a measure of the ratio of Darcy-law viscous force in the wetting liquid to interfacial tension force in curved menisci between the two phases. Statistical concepts of percolation theory give estimates of the length distribution of blobs created when the nonwetting phase loses continuity because of displacement by the wetting phase. These estimates agree with the few experimental data. Simple blob mobilization theory and experiments establish that the capillary number required to mobilize a blob is inversely proportional to its length in the direction of the Darcy-law pressure gradient; this and the predictions of percolation theory account for the observed capillary number correlation.
A parallel-plate, heterogeneous, sand-pack cell was constructed to study the effects of porous media heterogeneity on the displacement of water by a dense, immiscible phase, organic solvent. Tetrachloroethylene-water drainage capillary-pressure — saturation curves were measured for each of four sands used to create various lenses within the cell, and fitted with the Brooks-Corey capillary-pressure — saturation function using a nonlinear least-squares fitting routine. Tetrachloroethylene was injected under constant head conditions into the top of the initially static, water-saturated cell. The tetrachloroethylene behavior in the sand pack illustrated several key features of multiphase flow in heterogeneous porous media and demonstrated the critical role played by the capillary characteristics of the four sands employed.
This book presents the fundamental principles and applications of waterflooding oil-recovery techniques. It covers microscopic and macroscopic displacement efficiency, immiscible displacement in two dimensions, vertical displacement, waterflood design, and the influences of reservoir geology on waterflood design and operations.
Ph.D. Environmental Science and Engineering In this study, experiments were undertaken to examine both the dissolution of residual dense non-aqueous phase liquids (DNAPLs) in saturated porous media and the transport of the immiscible phase which produces these residuals. Dissolution experiments were carried out in a 75x100x100 cm tank containing Ottawa sand. A zone of residual DNAPL was created in the center of the tank and water samples were taken from a grid of needles that penetrated the sand at the downgradient end of the tank. Experimental data were used to determine contaminant concentrations as a function of velocity, the effect of DNAPL residuals on the permeability of the porous medium, and the interaction of two DNAPLs in a zone of mixed residuals. DNAPL flow was investigated by observing the movement of dye-containing DNAPLs in glass columns and in small sand tanks. Sands with different grain sizes and wetting histories were employed to determine the effect of these factors on the flow. The behavior of flow in the tanks was determined by excavating the sand and observing the distribution of the dye at different depths. In this manner, possible wall effects were avoided. Residual DNAPL saturations were also measured. Results of the dissolution experiments showed that concentrations equal to the aqueous solubility of the compound were easily obtained for the velocities used in this study (10 - 100 cm/day). Modeling of the contaminant plume indicated that there may have been a slight narrowing in the streamlines resulting from reduced permeability in the residual zone. The interaction of two different DNAPL residuals produced lower concentrations but was accounted for by treating the DNAPLs as an ideal solution. Observations made during the flow experiments indicated that a slight reduction in permeability can cause a DNAPL to flow laterally until it finds a more permeable spot through which to continue its downward progress. DNAPL residual saturations were found to be in the range of 15-40%. Model studies showed that the combined demands of relatively low concentrations and long source life found at field sites require sources that consist primarily of small horizontal pools rather than permeable zones of residual.
Thesis (Ph. D.)--Stanford University, 1988.
The dissolution of residual dense nonaqueous phase liquid (DNAPL) from a saturated porous medium. In:Petroleum Hydrocarbons and Organic Chemicals in Ground Water
- M R R L Anderson
- . F Johnson
- Pankow
Treatment of contaminated soils with aqueous surfactants
- W D J R Ellis
- . G Payne
- Mcnabb
Field experimental studies of residual solvent source emplaced in the groundwater zone
- M O Rivett
- S Feenstra
- J A Cherry
Surfactant enhanced solubilization of residual DNAPL: Column studies
- T S D Soerens
- . H Sabatini Andj
- Harwell
Migration of chlorinated hydrocarbons in groundwater
- M Y Corapcioglu
- . A Hossain
Is physical displacement of residual hydrocarbons a realistic possibility in aquifer restoration?
- J L Wilson
- S H Conrad
Proceedings of the Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention Detection and Restoration. NWWA/API Houston TX
- M O S Rivett
- . A Feenstra
- Cherry
Is physical displacement of residual hydrocarbons a realistic possibility in aquifer restoration? In:Proceedings of Petroleum Hydrocarbons and Organic Chemicals in Ground Water NWWA Houston TX
- J L Wilson
- . H Conrad
Removal of nonaqueous phase liquids using surfactants.Subsurface Restoration Conference Dallas TX
- J C Fountain