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A Continuous and Mechanistic Representation of Calcite Reaction-Controlled Kinetics in Dilute Solutions at 25°C and 1 Atm Total Pressure
Abstract
Calcite dissolution rates were measured using a free-drift technique at 25°C, 1 atm total pressure, and various\(P_{CO_2 } \) in deionized water. The data were corrected for gas phase disequilibrium and fitted to a kinetic expression derived by coupling the mechanistic models of Plummeret al. (1987a) and Chouet al. (1989) to the surface complexation model of Van Cappellenet al. (1993). Corrected dissolution and precipitation rate measurements from previous investigations were combined to our data set and fitted to the same expression. The following reactions provide an adequate description of the calcite dissolution and precipitation mechanism in dilute solutions:
for which the overall reaction rate is given by
where >i are the densities of surface complexes (mol/m2),a
i
are the activities of dissolved species and,k
i
are the rate constants corresponding to the above reactions. This rate equation satisfies the principle of microscopic reversibility and applies to both dissolution and precipitation reactions over a wide range of\(P_{CO_2 } \), pH and saturation states. The rate constants obtained from fitting the data set to Equation (3) are compatible with values reported by Plummeret al. and Chouet al., as well as yielding a very good estimate of the thermodynamic solubility constant of calcite, K
0sp.
... Nanoscale additives, on the other hand, can improve the rheological properties of surfactant and polymer-based nano fluids. The addition of nanoscale graphene to a water-based drilling fluid improved its lubricity and thermal stability in an experimental investigation and field trial [17]. ...
Nanotechnology's use in the oil and gas business is on the rise, as indicated by the number of studies conducted in recent years. This expansion has been fueled by the desire to produce additional game-changing technology that can address the industry's present difficulties. Several nanoparticles of various sizes and concentrations have been employed in a variety of studies. The study's scope included the use of nanotechnology in drilling and hydraulic fracturing fluids, oil well cementing, enhanced oil recovery (which included a transport study as well as foam and emulsion stability), corrosion inhibition, logging operations, formation fines control during production, heavy oil viscosity reduction, hydrocarbon detection, methane release from gas hydrates, and drag reduction in porous media. The stability of nanoparticles in a liquid medium and their transportability in reservoir rocks has been recognized as problems. Researchers utilized viscosities to assure stability, as well as surface-treated nanoparticles to aid stability and transportability. The majority of nanotechnology publications in the oil and gas business to far have been reports of laboratory experiments; consequently, further field trials are necessary for continued advancement of nanotechnology in this area. Nanoparticles are typically expensive, thus using the lowest nanoparticle concentration feasible while still obtaining an acceptable degree of desired performance can save money. As a result, optimization studies should be considered in future nanotechnology research.
... For k r of HCl/CaCO 3 , it varies between 1.26 and 5.8 × 10 −4 m s −1 . 22,[48][49][50][51] Here we take the mean value of 3.53 × 10 −4 m s −1 to calculate the Damkohler number. For acetic acid, the reactivity is much lower, ranging between 2.1 and 4.9 × 10 −6 m s −1 (ref. ...
We propose a simple microfluidic approach: Dissolution-After-Precipitation (DAP), to investigate regimes of carbonate rock dissolution and multiphase reactive transport. In this method, a carbonate porous medium is created in a...
... The dissolution of CaCO 3 has been extensively studied over the past decades (e.g. Morse and Berner, 1972;Ingle et al., 1973;Berner and Morse, 1974;Berner, 1976;Morse, 1978;Honjo and Erez, 1978;Plummer et al., 1978;Keir, 1980;Walter and Morse, 1985;Chou et al., 1989;Arakaki and Mucci, 1995;Morse and Arvidson, 2002;Gehlen et al., 2005a, b). It is in general described by a higher order dependence of the dissolution reaction on the degree of undersaturation of seawater: ...
... On the other hand, from a rationale based on surface complexation models (Arakaki and Mucci, 1995;Morse and Arvidson, 2002;Song et al., 2019;Van Cappellen et al., 1993), the effect of foreign cations zoning could also be interpreted as an extrinsic factor. These models are based on the idea that the speciation of surface sites can be significantly influenced by solution chemistry independently of the saturation state. ...
Chemical zoning of crystals is often found in nature. Crystal zoning can play a role in a mineral’s thermodynamic stability and in its kinetic response in the presence of fluids. Dissolution experiments at far-from-equilibrium conditions were performed using a sandstone sample containing calcite cement crystal patches. The surface normal retreat of the calcite crystals was obtained by vertical scanning interferometry (VSI) in their natural position in the rock. Dissolution rate maps showed contrasting surface dissolution areas within the crystals, in the same locations where electron microprobe (EMP) maps showed the presence of manganese (Mn) and iron (Fe) substitutions for calcium in the calcite structure. Iron zoning was only identified in combination with manganese. Maximum registered manganese contents were 1.9(9) wt.% and iron were 2(1) wt.%. Manganese zoning of only 0.9(5) wt.% resulted in around 40 % lower dissolution rates than the adjacent pure calcite zones. The combination of both Mn and Fe cation substitutions resulted in one order of magnitude lower dissolution rates compared to pure calcite in the same sample. These results show that mineral zoning can significantly affect reaction rates, a parameter that needs better understanding for the improvement of kinetic geochemical models at the pore scale.
... As a result of a cooperative interaction of different ions within the unit cell, the linear dependence of the kink velocity (v k ) on the saturation state will no longer hold true (Chernov, 2004;Zhang and Nancollas, 1998;Qiu and Orme 2008;Nehrke et al., 2007;Stack and Grantham, 2010;Wolthers et al., 2012;Nielsen et al., 2012). For calcite dissolution, specifically, mechanistic models suggest different site-specific reactions with different rate constants at the > CO 3 and > Ca + sites of the calcite surface (Arakaki and Mucci, 1995), which also imply different j AE s at the kink sites. This proposed mechanism in low ionic strength water will be altered by the complexation of surface sites from the major ions present in seawater (Ding and Rahman, 2018;Song et al., 2017). ...
We present the first examination of calcite dissolution in seawater using Atomic Force Microscopy (AFM). We quantify step retreat velocity and etch pit density to compare dissolution in seawater to low ionic strength water, and also to compare calcite dissolution under AFM conditions to those conducted in bulk solution experiments (e.g. Subhas et al., 2015). Bulk dissolution rates and step retreat velocities are slower at high and mid-saturation state (Ω) values and become comparable to low ionic strength water rates at low Ω. The onset of defect-assisted etch pit formation in seawater is at Ω ∼ 0.85 (defined as Ωcritical), higher than in low ionic strength water (Ω ∼ 0.54). There is an abrupt increase in etch pit density (from ∼10⁶ cm⁻² to ∼10⁸ cm⁻²) occurring when Ω falls below 0.7 in seawater, compared to Ω ∼ 0.1 in low ionic strength water, suggesting a transition from defect-assisted dissolution to homogeneous dissolution much closer to equilibrium in seawater. The step retreat velocity (v) does not scale linearly with undersaturation (1-Ω) across an Ω range of 0.4 to 0.9 in seawater, potentially indicating a high order correlation between kink rate and Ω for non-Kossel crystals such as calcite, or surface complexation processes during calcite dissolution in seawater.
Calcite dissolution kinetics at the single particle scale are determined. It is demonstrated that at high undersaturation and in the absence of inhibitors the particulate mineral dissolution rate is controlled by a saturated calcite surface in local equilibrium with dissolved Ca²⁺ and CO32– coupled with rate determining diffusive transport of the ions away from the surface. Previous work is revisited and inconsistencies arising from the assumption of a surface-controlled reaction are highlighted. The data have implications for ocean modeling of climate change.
We report the discovery of novel regimes of calcium carbonate dissolution in micron-scale confined spaces through microfluidic experiments. In the experiments, hydrochloric acid is injected into a microfluidic chamber with pre-deposited calcium carbonate solids. As the acid flow rate is decreased, the dissolution of calcium carbonate transits from a liquid/solid single-phase reactive transport regime to a gas/liquid/solid two-phase one. The two-phase regime further splits into two different regimes, one with fluctuating and the other with nonfluctuating gaseous CO2 phase. We name the three regimes as “Nongaseous”, “Gaseous Breathing”, and “Gaseous Nonbreathing”. The experimental observations are reproduced and interpreted by mathematical modeling. Results show that the regimes are controlled by the ratio of H⁺ concentration and saturated CO2 concentration, the Peclet number and the second Damkohler number. Dimensionless diagrams distinguishing different regimes are presented and an empirical relationship is proposed. Our results offer insights into various engineering and natural processes, e.g., geological carbon storage, petroleum reservoir acidizing, Karst dissolution, and others that are governed by small scale multiphase reactive flow physics.
Reaction kinetics between calcite and acid systems have been studied using the rotating disk apparatus (RDA). However, simplifying assumptions have been made to develop the current equations used to interpret RDA experiments to enable solving them analytically in contrast to using numerical methods. Previous work has revealed inadequacies of some of these assumptions, which necessitates the use of a computational fluid dynamics (CFD) model to investigate their impact on the RDA results. The objectives of the current work are to develop a calibrated CFD and proxy model to simulate the reaction in the RDA and use this model to estimate the diffusion coefficient and the reaction rate coefficient of the reaction in the RDA.
The present work developed the first calibrated CFD model to determine the diffusion coefficient and the reaction rate coefficient in the RDA with minimum assumptions in the hydrochloric acid (HCl) carbonate reaction. More specifically, the model relaxes the constant fluid properties, infinite acting reactor boundaries, and constant reaction surface area assumptions. The proxy model obtained results in reduced computational time with minimal compromise on accuracy. Finally, the proposed model showed an improvement of 63% in predicting the reaction kinetics between calcite and HCl compared to traditional methods.
The dissolution of CaCO₃ minerals in the ocean is a fundamental part of the marine alkalinity and carbon cycles. While there have been decades of work aimed at deriving the relationship between dissolution rate and mineral saturation state (a so-called rate law), no real consensus has been reached. There are disagreements between laboratory- and field-based studies and differences in rates for inorganic and biogenic materials. Rates based on measurements on suspended particles do not always agree with rates inferred from measurements made near the sediment–water interface of the actual ocean. By contrast, the freshwater dissolution rate of calcite has been well described by bulk rate measurements from a number of different laboratories, fit by basic kinetic theory, and well studied by atomic force microscopy and vertical scanning interferometry to document the processes at the atomic scale. In this review, we try to better unify our understanding of carbonate dissolution in the ocean via a relatively new, highly sensitive method we have developed combined with a theoretical framework guided by the success of the freshwater studies. We show that empirical curve fits of seawater data as a function of saturation state do not agree, largely because the curvature is itself a function of the thermodynamics. Instead, we show that models that consider both surface energetic theory and the complicated speciation of seawater and calcite surfaces in seawater are able to explain most of the most recent data. This new framework can also explain features of the historical data that have not been previously explained. The existence of a kink in the relationship between rate and saturation state, reflecting a change in dissolution mechanism, may be playing an important role in accelerating CaCO₃ dissolution in key sedimentary environments.
Nanotechnology has grown rapidly in both research and applications over the past two decades including in the upstream petroleum industry. A recent hot area for studying nanotechnology has been oilfield scale management. The formation of oilfield scale deposits such as calcium carbonate and Group II sulfate scales in conduits and on equipment, both downhole and topside, can cause serious loss of hydrocarbon production and unwanted downtime. Scale management is expensive to the field operator, mostly due to downtime causing deferred or loss of production. Many types of nano-based materials and treatments have been developed to combat this problem, most of them containing one form or another of an organic scale inhibitor. In this review, we reviewed the various types of nanotechnologies that have been developed and include comparisons to conventional treatments where available. The nanotechnologies include nanoemulsions, nanoparticles, magnetic nanoparticles, polymer nanocomposites, carbon-based nanotubes, and other miscellaneous technologies. Several nanoproducts developed for squeeze treatments indicate improved squeeze lifetime compared to conventional squeeze treatments. Other potential benefits include improved thermal stability for high-temperature wells, reduced formation damage for water-sensitive wells, and environmental impact.
