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Effective mud removal is a prerequisite to attain the cement coverage necessary for good zonal isolation. Because of this, the oilfield industry has dedicated considerable attention to the topic of mud displacement over the past 60 years. The first 2D annular displacement simulator was introduced in the 1990s and it is now widely available. The res...
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... For instance, Kroken et al. [17] demonstrated that a greater density contrast between the displacing and displaced fluids in inclined wells and low flow rates can enhance the buoyancy of the displaced fluid, facilitating a vertical flow of the heavier fluid from the wider annular side at the top to the narrower side at the bottom, thereby increasing displacement efficiency. Theoretical research could be further enhanced to offer insights into potential challenges associated with optimizing the design of fluids prior to cementing operations [18,19]. An ideal model should be comprehensive, enabling consideration of all relevant factors, accurate prediction, and efficient computation. ...
... Based on Equations (18) and (19), when Yi = H, the thickness of the layer of drilling fluid retained on the wall is 0. Substitute Yi = H into these two equations, we obtain ...
To guarantee that the cement sheath has a sealing effect, it is best to replace the drilling fluid entirely and fill the annulus with cement slurry throughout the cementing process. A significant driving power and high stability at the interface between the cement slurry and drilling fluid are often necessary for achieving a high displacement efficiency. It is important that a comprehensive theoretical characterization is established on the thickness and location of drilling fluid retention and the conditions to prevent the formation of drilling fluid retention. In this study, firstly, the characteristics of annulus fluid shear stress distribution are analyzed by establishing the differential equation of shear stress distribution. Subsequently, the calculation model of the drilling fluid retention layer’s thickness is constructed. Subsequently, the impact of cement slurry and drilling fluid properties, eccentricity of the casing, and additional variables on the annular wall’s drilling fluid retention thickness are scrutinized. The quantitative conditions for preventing drilling fluid retention are also analyzed (i.e., Equation (23)). Based on the newly developed model, a case study is conducted to show the significance of the new model. This offers a theoretical foundation for enhancing cement injection displacement efficiency and cementing performance optimization.
... Tardy and Bittleston [15] created a (2+1)D finite volume method with a narrow gap assumption and averaging the fluid volume fraction and velocity along the radial direction to study the mud displacement in the annulus. Based on this model, Tardy et al. [16] presented a simplified 3D model of the entire wellbore by segmenting the wellbore into many sections and analyzing the cement displacement in each section. This model was later used to analyze a few wells in the Gulf of Mexico [17]. ...
... [ [15][16][17]20,21] (2+1)D finite volume. ...
Successful design and execution of slim-hole cementing operations depend on reliable prediction of the annular pressure and the efficiency of mud displacement by cement. A 3D model of the flow inside the casing and in the annulus during mud displacement/cement placement operations was created. The yield-power-law fluid model was used for the rheological behavior of mud, spacers, and cement. Mud displacement was analyzed by splitting the well into multiple sections and analyzing the efficiency of mud removal by spacers and cement, as well as the associated pressure gradients in each section for applicable combinations of pump rate and casing rotation speed. The results from the various computational steps were then integrated to compute the overall pressure and cement placement efficiency during the cementing operation. Using the new 3D model, a field case study was performed for a slim hole casing cementation on an unconventional shale well. The simulated peak surface pressure was only 0.3% lower than the measured data, and the trend of the pressure matched the measured data. This work provides a new tool for the well construction industry to predict and analyze the pressure during complicated cementing operations, thereby enabling safer and more cost-effective operations.
... The settlement of tailing flocs is an autonomous/passive, nonuniform bonding process driven by chemical agents such as gravity forces and chemical flocculants, resulting in the formation of bottom mud bed with a higher solid concentration [108,109]. The researches simply believing that increasing shear force can improve the dewatering efficiency. ...
... The vortex formation also indicates a stratified displacement pattern. The lighter (gas) material tends to occupy the upper part of the tube when buoyancy forces are sufficiently large, resulting in a stratified displacement pattern [33]. In addition, liquid waves reach the top of the tube, cutting off the cross-section of the gas in certain cases at higher velocities. ...
The increasing share of renewable electricity in the grid drives the need for sufficient storage capacity. Especially for seasonal storage, power-to-gas can be a promising approach. Biologically produced methane from hydrogen produced from surplus electricity can be used to substitute natural gas in the existing infrastructure. Current reactor types are not or are poorly optimized for flexible methanation. Therefore, this work proposes a new reactor type with a plug flow reactor (PFR) design. Simulations in COMSOL Multiphysics ® showed promising properties for operation in laminar flow. An experiment was conducted to support the simulation results and to determine the gas fraction of the novel reactor, which was measured to be 29%. Based on these simulations and experimental results, the reactor was constructed as a 14 m long, 50 mm diameter tube with a meandering orientation. Data processing was established, and a step experiment was performed. In addition, a kLa of 1 h−1 was determined. The results revealed that the experimental outcomes of the type of flow and gas fractions are in line with the theoretical simulation. The new design shows promising properties for flexible methanation and will be tested.
... A new generation 3-D simulator was more recently introduced by Tardy et al. [58], where a high-resolution annular displacement model, accounting for the complex 3-D annulus shape with full determination of axial and azimuthal flows was developed. Tardy [59] provided theoretical details of the model where the lubrication theory with narrowgap approximation was used to solve the 3-D velocity and concentration fields along with a 2-D elliptic pressure equation. ...
During drilling operations, effective displacement of fluids can provide high-quality cementing jobs, ensuring zonal isolation and strong bonding of cement with casing and formation. Poor cement placements due to incomplete mud removal can potentially lead to multiple critical operational problems and serious environmental hazards. Therefore, efficient mud removal and displacement of one fluid by another one is a crucial task that should be designed and optimized properly to guarantee the zonal isolation and integrity of the cement sheath. The present work provides an overview of the research performed on mud removal and cement placement to help the industry achieve better cementing jobs. An extensive number of investigations have been conducted in order to find some key techniques for minimizing the cement contamination and obtaining maximum displacement efficiency. Yet, even after implementing those techniques, the industry happens to encounter poor cementing jobs. The present review aims to assist with evaluating the current theories, methodologies, and practical techniques, in order to possibly identify the research gaps and facilitate the way for further improvements.
... Both problems are described by a similar elliptic Poisson equation for pressure with mixed boundary conditions for pressure and its gradient. The detailed description of the model and equations of cement placement in an annulus can be found in (Bittleston and Hassager, 1992;Walton and Bittleston, 1991;Pelipenko and Frigaard, 2004a;Tardy and Bittleston, 2015;Tardy et al., 2017;Pelipenko and Frigaard, 2004b;Bittleston et al., 2002;Pelipenko and Frigaard, 2004c;Frigaard Pelipenkoet al., 2003;Dooply et al., 2016). A 3D model of the displacement of drilling mud by cement in the annular gap is presented in (Tardy et al., 2017;Tardy, 2018). ...
... The detailed description of the model and equations of cement placement in an annulus can be found in (Bittleston and Hassager, 1992;Walton and Bittleston, 1991;Pelipenko and Frigaard, 2004a;Tardy and Bittleston, 2015;Tardy et al., 2017;Pelipenko and Frigaard, 2004b;Bittleston et al., 2002;Pelipenko and Frigaard, 2004c;Frigaard Pelipenkoet al., 2003;Dooply et al., 2016). A 3D model of the displacement of drilling mud by cement in the annular gap is presented in (Tardy et al., 2017;Tardy, 2018). Although the flow field is three-dimensional, the pressure equation is two-dimensional, which was made possible using the thin-layer (lubrication) approximation. ...
Numerical simulators for the design of oilfield services technologies are required to be fast and robust, hence the implementation of underlying mathematical models is expected to be highly efficient. We present an optimized numerical algorithm based on the multigrid approach for solving the pressure equation in 2D problems of fluid-fluid displacement. This type of problems arise in oilfield services applications, such as drilling, cementing, hydraulic fracturing and EOR. The displacement of fluids with different properties in a narrow annular gap (drilling, cementing) or a slot (hydraulic fracturing, production) is governed by the 2D width-averaged model in the lubrication approximation. In numerical implementation, the most time-consuming is the elliptic Poisson pressure equation, which has coefficients with discontinuities (jumps) in the case of displacement of fluids with viscosity contrast. Specifically for this case of discontinuous coefficients, we designed and implemented numerically the black-box multigrid algorithm, which resolves the divergence issue typical of standard realization of multigrid algorithm using bilinear prolongation operators. The algorithm is tested on a number of matrices corresponding to discretization of elliptic equation at rectangular staggered meshes with different resolution. The performance of the algorithm is compared against several other sparse solvers available for commercial use: smoothed aggregated algebraic multigrid (PyAMG software package), direct sparse solver from Intel MKL library (DSS), Bi-Conjugate Gradient-Stabilized solver preconditioned by ILUT factorization implemented into BLAS package, and our in-house Conjugated Gradient algorithm preconditioned by ILU(2) factorization. It was found that the performance of the black-box multigrid solver is significantly higher (from 7x to 30x in terms of CPU time depending on the mesh resolution) as compared to the closest solver under consideration, which allows us to recommend this solver for implementation into existing 2D drilling simulators, fracturing design tools, cement placement and production simulators.
... An example is within cement displacement complexities for engineering purposes, 31 where the desirable insight is pressure distributions and the cement displacement efficiency. 32 Numerical treatment of viscoplastic flow problems has significantly improved over the last decades. Researchers interested in analysing such flows are, however, still limited by the computational cost associated with their solution. ...
We present the extension of an efficient and highly parallelisable framework for incompressible fluid flow simulations to viscoplastic fluids. The system is governed by incompressible conservation of mass, the Cauchy momentum equation, and a generalised Newtonian constitutive law. In order to simulate a wide range of viscoplastic fluids, we employ the Herschel-Bulkley model for yield-stress fluids with nonlinear stress-strain dependency above the yield limit. We utilise Papanastasiou regularisation in our algorithm to deal with the singularity in apparent viscosity. The resulting system of partial differential equations is solved using the IAMR (Incompressible Adaptive Mesh Refinement) code, which uses second-order Godunov methodology for the advective terms and semi-implicit diffusion in the context of an approximate projection method to solve adaptively refined meshes. By augmenting the IAMR code with the ability to simulate regularised Herschel-Bulkley fluids, we obtain efficient numerical software for time-dependent viscoplastic flow in three dimensions, which can be used to investigate systems not considered previously due to computational expense. We validate results from simulations using this new capability against previously published data for Bingham plastics and power-law fluids in the two-dimensional lid-driven cavity. In doing so, we expand the range of Bingham and Reynolds numbers which have been considered in the benchmark tests. Moreover, extensions to time-dependent flow of Herschel-Bulkley fluids and three spatial dimensions offer new insights into the flow of viscoplastic fluids in this test case, and we provide missing benchmark results for these extensions.
The well trajectory of horizontal wells are constantly changing due to the variation of well inclination and azimuth with depth, leading to a large difference of displacement efficiency in the annulus compared to a vertical well. In low pressure and leakage formations, optimizing injection parameters to improve displacement efficiency is a hot and difficult research topic for researchers and field engineers, particularly the complex well. A fluid flow model inside the casing and annulus was established during primary cementing under an eccentric casing. Pressure distribution in the eccentric and concentric annuli were compared with the field data. Based on the principle of the maximum circulation pressure being lower than formation leakage pressure, the injection rate and fluid density were optimized to improve displacement efficiency, using Computational Fluid Dynamics (CFD) methods and investigating the mud retention volume on the wall. The results indicated that the pressure model in a casing eccentricity with an error of 1% to 3.5% is in good agreement with the actual pump pressure. Frictional pressure loss in the eccentric annulus was 13% to 25% lower than in the concentric annulus. Appropriately increasing the fluid density difference (spacer and lead slurry), the mud retention volume in the annulus of the horizontal section decreased significantly, while increasing the injection rate at the wellhead had little influence on displacement efficiency. The sequence of displacement efficiency from high to low was horizontal section > deflecting section > vertical section. The results of this study allow a better understanding of casing eccentricity effect on circulation pressure and equivalent circulation density (ECD) distributions in the annuls. The complex displacement mechanism analysis for the horizontal, deflecting, and vertical sections provides practical guidance in improving displacement efficiency by optimizing the most effective operation parameters.
Wellbore irregularities turn the narrow eccentric annulus of primary cementing into a fully three-dimensional (3D) flow geometry. Here we explore the effects of coupling the borehole geometry, reconstructed from high frequency caliper data, with 3D computations of the displacement flow. Displacement flows through circular boreholes with enlargements of varying depths and wavelengths tend to result in both enhanced secondary flows and in residual drilling mud. Short wavelength deep enlargements generally have larger percentage of residual mud. We then perform a frequency analysis of typical caliper data from Northwest Canada, showing that the borehole geometry may typically be reconstructed using the lowest 3-5 dominant frequencies. We present example computations of displacement flows through these geometries. Although the underlying dynamics are those of more uniform annuli, these computations do reveal in that small changes in geometric description can lead to noticeable changes in the displacement mechanics, especially in the fluid present at the walls of the annulus. The conclusion is that borehole irregularity can make a significant difference in cementing horizontal wells, which are anyway already troublesome.
The quality of cement placement in primary cementing depends on many facets of the cementing procedure. In this paper, we simulate the fluid displacement process of a typical horizontal well in Northern British Columbia. We analyze how variations in some of the common cementing practices may improve the displacement efficiency. By using excess cement volume, the residual mud can be gradually removed as long as there is a sufficient pressure gradient to yield the mud. Increasing the centralizer usage is demonstrably effective in removing residual mud in the deviated section, and the eccentricity is significantly improved. Performing staged cement allows improvement in displacement by allowing flexibility in frictional pressure loss management (often crucial in long horizontal wells). Targeting different strategies for vertical and deviated sections results in improved efficiencies.
