Miscible Displacement Processes Research Articles

Measuring miscible fluid displacement in porous media with magnetic resonance imaging

AbstractThe development of new quantitative magnetic resonance imaging (MRI) technologies open new opportunities for measurements of mass transport in porous media. The current work examines a simple miscible displacement process of H2O and D2O in porous media samples. Laboratory measurements of dispersion in porous media traditionally monitor the effluent intensity of an injected tracer. We employ MRI to obtain quantitative water saturation profiles, and to measure dispersion in rock core plugs. The saturation profiles are modeled with PHREEQC, a fluid transport modeling program. We demonstrate how independent magnetic resonance measurements can be employed to estimate three important input parameters for PHREEQC, mobile porosity, immobile porosity, and dispersivity. Bulk Carr Purcell Meiboom Gill (CPMG) T2 distribution measurements were undertaken to estimate mobile and immobile porosity. Bulk alternating‐pulsed‐gradient‐stimulated‐echo (APGSTE) measurements were undertaken to measure dispersivity. The imaging method employed, T2 mapping Spin Echo Single Point Imaging (SE‐SPI), also provides information about the pore size distributions in the rock cores, and how the fluid occupancy of the pores changes during the displacement process.

An Experimental Investigation of Fracture Impacts on the Dispersion of Miscible Displacement Processes: Qualitative Analysis

Dispersion phenomena of miscible displacement processes conducted on porous media have been investigated by many researchers in different engineering field in the past 50 years. In microscopic scale, the pore size distribution has been shown to cause dispersion of two miscible displacement fluids flowing through laboratory core scale. In field scale, the heterogeneity of reservoir formation has been shown to be a main cause of dispersion. One of the heterogeneities of reservoir formation is the presence of networks of fractures. The roles of network fractures on dispersion have not been investigated in enhanced oil recovery miscible displacement processes. In this work, the effect of fractures on dispersion was investigated by conducting miscible displacement laboratory tests on micromodels. The tests were performed under two different injection rates with two different fracture orientations. The results show that breakthrough time is reduced when the fracture is present in the micromodel. Higher pore volume injection of displacing fluid is needed for fractured patterns to reach normalized concentration of one in comparison with the homogeneous one. The experimental results suggest that the breakthrough curve of the fractured system has three distinct regions in comparison with the homogeneous system. Also, the results show that a system with a fracture perpendicular to the flow direction acts as a dead end pore system.

Stability analysis of reversible reactive flow displacements in porous media

The effects of reversibility on the viscous fingering of miscible reactive flow displacement processes are examined. A model, where the viscosity mismatch between the reactants and the product triggers instability is adopted. The stability of the flow displacement is examined in the case of initial sharp front between the two reactants as well as when the reactants are given time to diffuse. In the case of a sharp front, a transformation allows to map the reversible case to that of the non-reversible one and an analysis of the effects of chemical reversibility is presented. In general, faster attenuation in the development and growth of instability is reported as the reversibility of the chemical reaction increases. However, it was found that reversibility can actually enhance the instability when a critical reversibility coefficient that depends on the mobility ratios of the chemical species, is exceeded. Different trends for the effects of reversibility were obtained for initially diffusing chemical reactants and the results are discussed in terms of the mobility ratios of the different species. It was found that the effects of stronger chemical reversibility on the stability of the flow are qualitatively similar to those induced by slower chemical reactions in non-reversible cases, however quantitative differences are reported and discussed.

Pore Level Simulation of Miscible Injection with Gravity Domination

Gravity assisted miscible CO2 injection into oil reservoirs is an efficient method of enhancing oil recovery. CO2 injection into aquifers for sequestration purposes is another application of miscible displacement under gravity control. This paper reports pore scale simulation studies to determine the role of different parameters on the frontal stability of the miscible displacement process under gravity.The simulation studies were performed using the Finite Element Analysis technique. The simulation model was initially validated by matching results with flow visualization experimental studies using glass micromodels. The Navier-Stokes, continuity and convection-diffusion equations were used in the simulation instead of ideal Darcy law. Wide ranges of parameters applicable for Enhanced Oil Recovery and CO2 sequestration have been used in the sensitivity study. Dip angles(θ) between 0° and 180° (for up- dip and down-dip situations), different domain velocities, density differences of 50 to 900kg/m3 between the injecting and displaced fluids and viscosity ratios from 1 to 50 (to include light and heavy oils) have been investigated. Snapshots were captured in each simulation case for visual comparison of the frontal advancement. In addition, breakthrough saturation was plotted against cos (θ) to quantify the competition between viscous and gravity forces in gravity dominated miscible displacement process.The pore scale study suggests that stability of a miscible process can be influenced by several factors. When gravity acts in favor of displacement and there is a moderate to large density difference, angular tilt is the most important parameter influencing displacement. When the density difference is small then the mobility ratio and flow velocity also play a role. When gravity opposes displacement and buoyancy forces are dominating, results show little sensitivity to the actual tilt angle. Better displacement is seen for lower density difference and for higher flow velocity, while, again, the mobility ratio only impacts on displacement when the density difference is quite small.

IMPROVEMENT OF FRACTIONAL FLOW MODEL FOR MISCIBLE DISPLACEMENT PROCESS: AN EXPERIMENTAL INVESTIGATION IN SINGLE FRACTURED POROUS MEDIUM

Most of the reservoirs in Iran are heterogeneous fractured carbonate reservoirs. Heterogeneity causes an earlier breakthrough and an unstable front, which leads to a lower recovery. In this study, a series of experiments was conducted whereby the n-Heptane displaced n-Decane in glass micromodels having different fracture geometries. Experimental data from image analysis of miscible displacement processes are used to modify the fractional flow equations by a heterogeneity factor. It is shown that the heterogeneity factor in the modified equations can be expressed as a function of fracture length and orientation.

Micro-Model Experimental Study of Fracture Geometrical Effect on Breakthrough Time in Miscible Displacement Process

The miscible displacement process appears to be an increasingly feasible method for the extraction of oil from depleted reservoirs. However, there is a lack of fundamental understanding of how fracture geometrical characteristics impact the oil recovery efficiency in this type of enhanced oil recovery technique. In this work, a series of experimental tests were conducted whereby the n-Heptane as a solvent displaced n-Decane in the glass micro-models having different fracture geometries. It has been observed that the breakthrough time is decreased with increasing the fractures' length. In contrast, breakthrough time is increased when increasing the fractures orientation angle related to flow direction. A correlation has been presented for the breakthrough time as a function of fracture length and its orientation.

Compositional Space Parameterization: Multicontact Miscible Displacements and Extension to Multiple Phases

Summary We generalize the compositional space parameterization (CSP) approach, which was originally developed for immiscible two-phase multicomponent problems, to multicontact miscible displacements. The tie-line based parameterization method improves both the accuracy of the phase-behavior representation as well as the efficiency of equation of state (EOS) computations in compositional flow simulation. For immiscible compositional simulation, compositional space adaptive tabulation (CSAT) can be used to avoid most of the redundant EOS calculations. Because the supercritical region cannot be parameterized using tie-lines, the original CSAT approach is not effective for modeling multicontact miscible gas injection processes. To deal with supercritical compositions, a supercritical state criteria (SSC) algorithm based on adaptive tabulation of the minimal critical pressure (MCP) tie-lines is proposed. For general-purpose simulation of miscible and immiscible compositional displacement processes, we combined the adaptive CSAT strategy in the region of tie-line extensions and the adaptive SSC scheme; we refer to the overall framework as CSAT. Results of several challenging tests of practical interest indicate that the general CSAT strategy is quite robust and that it leads to an order of magnitude gain in computational efficiency. We also describe the extension of the CSP framework for mixtures that form more than two phases.

Analysis of the convective dispersive transport in porous media

The finite-control volume technique is used to solve the convection–dispersion equation in cylindrical coordinates. In the model presented, the dispersion coefficient is dependent on both velocity and diffusion coefficient. The solution allows analyzing the dispersion transport of a slug in a steady radial flow from an injection well fully penetrating a homogeneous reservoir of uniform thickness and finite drainage area. The solution is used to study the effects of a number of parameters, like dispersivity, tortuosity, porosity, and injection rate on the mixing process. For the range of parameters investigated, and for the homogeneous porous medium simulated, the optimal solvent slug size appears to slightly vary around the vicinity of 0.1 pore volume, for an arbitrary position taken at a dimensionless radius r D = 0.5. The optimal solvent slug size appears to slightly increase with increasing porosity and dispersivity, and to decrease with increasing tortuosity. The finite-volume technique is favored over the finite-difference technique because it is known to eliminate the detrimental effects of numerical dispersion. The convection–dispersion equation arises in the simulation of miscible displacement processes where front smearing resulting from numerical dispersion can distort the behavior of the displacement process. This front smearing can, for instance, lead to false predictions of breakthrough times and optimal slug sizes. This in return causes poor reservoir management and inadequate economic forecast of EOR processes.

The linear stability of double-diffusive miscible rectilinear displacements in a Hele-Shaw cell

We investigate the viscous instability of a miscible displacement process in a rectilinear geometry, when the viscosity contrast is controlled by two quantities which diffuse at different rates. The analysis is applicable to displacement in a porous medium with two dissolved species, or to displacement in a Hele-Shaw cell with two dissolved species or with one dissolved species and a thermal contrast. We carry out asymptotic analyses of the linear stability behaviour in two regimes: that of small wavenumbers at intermediate times, and that of large times. An interesting feature of the large-time results is the existence of regimes in which the favoured wavenumber scales with t − 1 / 4 , as opposed to the t − 3 / 8 scaling found in other regimes including that of single-species fingering. We also show that the region of parameter space in which the displacement is unstable grows with time, and that although overdamped growing perturbations are possible, these are never the fastest-growing perturbations so are unlikely to be observed. We also interpret our results physically in terms of the stabilising and destabilising mechanisms acting on an incipient finger.

Application of Acoustic Wave Propagation Analysis Methods for Monitoring a Miscible Mixing Zone in Porous Media

The Biot's acoustics theory, which describes acoustic wave propagation in a porous medium, and computer simulation techniques were utilized to model the behavior of acoustic waves entering and leaving a mixing zone in a miscible displacement in porous media. The results indicate that the angles of waves produced by a mixing zone are equal to angles of waves produced by an abrupt fluid-fluid interface. Therefore, acoustic methods and a relationship between the incident, reflection, and transmission angles can be used to determine the location and thickness of the mixing zone during a miscible displacement process in porous media.

Eigenvalues define conditions of stability in liquid-liquid miscible displacement process

A miscible displacement process is primarily governed by both convective flow and hydrodynamic dispersion. The proper classification of stability condition in the miscible displacement process is a major requirement for a successful field application of this enhanced crude oil recovery mechanism. This paper derives characteristics functions, the eigenfunctions, which provide guidelines for achieving flow stability in miscible displacement processes. A growth parameter, the eigenvalue, shows the necessary and sufficient conditions for stability in the liquid-liquid miscible displacement process. The critical velocity and wavelength necessary for stability are defined for the miscible displacement process. Journal of the Nigerian Association of Mathematical Physics Vol. 8 2004: pp. 167-173

The modelling of instabilities in liquid-liquid miscible displacement processes by the Galerkin-based finite element method

The Galerkin-based finite element method has been used to successfully simulate the propagation of instabilities in the liquid-liquid miscible displacement process. The convective-dispersion equation is sufficient to model the liquid-liquid miscible displacement process under unstable conditions. The investigations reveal: i. An unconditional instability which will not disappear with time, ii. The rate of growth of the instabilities, tended to increased proportionally to a number to the M power, where M is the mobility ratio, iii. The propagation of instabilities can be achieved through the actions of viscous, gravity and heterogeneous forces, and iv. Heterogeneity in permeability introduces a macroscopic dispersion effect that attempts to stabilize the instabilities. Journal of the Nigerian Association of Mathematical Physics Vol. 8 2004: pp. 173-176

Experimental and Numerical Studies of Gas/Oil Multicontact Miscible Displacements in Homogeneous and Crossbedded Porous Media

Summary We investigate oil recovery from multicontact miscible (MCM) gas injection into homogeneous and crossbedded porous media, using a combination of well-characterized laboratory experiments and detailed compositional flow simulation. All simulator input data, including most EOS parameters, were determined experimentally or from the literature produced fluids in all experiments were found not to be in compositional equilibrium. This was not predicted by the simulator, giving a poor match between experimental and simulated oil recoveries. The match was significantly improved for the cross-bedded displacements by using alpha factors derived from the MCM displacements in the homogeneous pack. Introduction The recovery of oil by miscible gas injection has been a subject of interest and research in petroleum engineering for more than 40 years (Stalkup 1983). In a first-contact, miscible (FCM) displacement, the gas and oil mix instantly in all proportions. No capillary forces exist, so, in principle, residual oil saturation is zero, and 100% oil recovery should be achieved. In practice, many phenomena conspire to limit the efficiency of the miscible flooding process, including viscous fingering, gravity override, and permeability heterogeneity. Moreover, it is often not economical, and sometimes not technically feasible, to inject a gas that is first-contact miscible with the oil. Instead, the injected gas is designed to develop miscibility with the oil by mass transfer during the displacement. This is a so-called MCM gas injection. If the bulk of the mass transfer is from the gas to the oil, then the displacement is termed a condensing drive. If most of the mass transfer is from the oil to the gas, then it is termed a vaporizing drive. In most cases, however, because of the multicomponent nature of oil and gas, the mass transfer is actually a mixture of both these cases, and the displacement is termed a condensing-vaporizing drive. Small-scale heterogeneities can have a significant impact on recovery efficiency (Jones et al. 1995; Jones et al. 1994; Kjonsvik et al. 1994), yet they cannot be modeled explicitly in field-scale simulations. Some of the most common small-scale heterogeneities found in sandstone reservoirs are laminations. However, because laminations have a small size and are generally at an angle to the principal flow direction, their influence onfluid flow is one of the most difficult features to predict numerically. There is a significant amount of literature describing systematic investigations of first-contact miscible and immiscible displacement processes in laminated sandstones (Huang et al. 1995, 1996; Ringrose et al. 1993; Kortekaas 1985; Honarpour et al. 1994; Hartkamp-Bakker 1991, 1993; McDougall and Sorbie 1993; Marcelle-DeSilva and Dawe 2003; Borresen and Graue 1996; Roti and Dawe 1993; Dawe et al. 1992; Caruana and Dawe 1996; Caruana 1997). Both experimental and simulation studies show that significant volumes of oil can be trapped by capillary forces during immiscible displacements (Huang et al. 1995, 1996; Ringrose et al. 1993; Kortekaas 1985; Honarpour et al. 1994; Hartkamp-Bakker 1991, 1993; McDougall and Sorbie 1993; Marcelle-DeSilva and Dawe 2003; Borresen and Graue 1996; Roti and Dawe 1993; Dawe et al. 1992; Caruana and Dawe 1996; Caruana 1997). However, the influence of these heterogeneities on MCM displacements, during which capillary forces change from being very significant when gas is first injected to negligible once miscibility has developed, has not yet been investigated. Indeed, the only comparisons of well-characterized MCM displacement experiments and detailed simulations reported in anywhere in the literature are those of Burger and colleagues (Burger and Mohanty 1997; Burger et al. 1996; Burger et al. 1994).

New Approach in Gas Injection Miscible Processes Modelling in Compositional Simulation

Abstract A number of factors must be considered in the design of miscible displacement processes. This paper discusses a new approach that relates primarily to the laboratory and modelling studies that precede the EOS-based compositional simulation of reservoir performance during the vapourizing/condensing gas drive process. The phase behaviour of a solvent/oil system and determination of miscibility conditions by various special PVT experiments (including the swelling test, RBA, slim tube test, and the continuous multiple-contact experiment) are reviewed along with their importance in building an accurate EOS model to be used in compositional simulation. In addition to experimental PVT data, a special core flow test design for measuring the relative permeabilities to generated fluids by forward/reverse multiple contact experiments is discussed. Based on laboratory PVT and SCAL data, a novel interfacial tension-dependent model of relative permeability and capillary pressure data is presented along with the advantages if incorporated into commercial EOS-based compositional simulation software packages. Introduction Mass transfer between the gas and oil components dominates the displacement characteristics of miscible or near-miscible floods. The overall displacement efficiency of any oil recovery displacement process can be considered conveniently as the product of microscopic and macroscopic displacement efficiencies. In equation form: where E = overall displacement efficiency, ED = microscopic displacement efficiency, and EV = macroscopic (volumetric) displacement efficiency. Microscopic displacement relates to the displacement or mobilization of oil at pore scale. That is, ED is a measure of effectiveness of the displacing fluid in moving (mobilizing) the oil at those places in the rock where the displacing fluid contacts the oil. ED is reflected in the magnitude of the residual oil saturation, Sor, in the regions contacted by the displacing fluid. Macroscopic displacement efficiency relates to the effectiveness of the displacing fluid(s) in contacting the reservoir in a volumetric sense. EV is a measure of how effectively the displacing fluid sweeps out the volume of a reservoir, both areally and vertically, as well as how effectively the displacing fluid moves the displaced oil toward production wells. It is desirable in an Enhanced Oil Recovery (EOR) process that the values of ED and Ev, and consequently E, approach 1. An idealized EOR process would be one in which the displacing fluid removed all oil from the pores contacted by the fluid (Sor →0). Several physical/chemical interactions occur between the displacing fluid and the oil that can lead to efficient microscopic displacement (low Sor). These include miscibility between the fluids, decreasing the interfacial tension (IFT) between the fluids, oil volume expansion, and reducing oil viscosity. The maintenance of a favourable mobility ratio between displaced and displacing fluids also contributes to better microscopic displacement efficiency. EOR processes are thus developed with consideration of these factors. The goal of an acceptable EOR fluid is to maintain favourable interaction(s) as long as possible during the flooding process. In enhanced recovery operations, oil entrapment occurs due to complex interactions between viscous, gravity, and capillary forces.

Modelling Physical Dispersion in Miscible Displacement-Part 1: Theory and the Proposed Numerical Scheme

Abstract Physical dispersion, comprising molecular diffusion and mechanical dispersion, is one of the primary fluid mixing mechanisms in reservoir processes dominated by compositional change. Its effect controls the characteristics and magnitude of oil recovery by miscible displacement. Standard compositional simulators used to model miscible displacement generally do not include physical dispersion effects and solve the governing equations by first order finite-difference scheme with singlepoint upstream weighting of mobilities. This approach leads to unphysical smearing of fronts (known as numerical dispersion), which is assumed to compensate for the physical dispersion. Unfortunately, this assumption is valid only for one-dimensional problems under very restrictive conditions and can lead to erroneous results in multiple dimensions. The incorporation of physical dispersion in geologically complex models, such as the ones described by non-orthogonal corner-point grids, requires the use of advanced techniques of flux approximation to retain both physical and numerical accuracy. The use of the tensorial form of the permeability or dispersion coefficient becomes a necessity for convective or dispersive transport when flows are not aligned to the principal coordinate axes, which is almost always the case in practical reservoir simulation. In this paper, a new dispersive flux-continuous scheme based on a multi-point control volume procedure is developed to allow the inclusion of the full tensor form of physical dispersion into compositional simulation of miscible displacement on 3-dimensional hexahedron structured corner-point grids. Introduction Gas injection into oil reservoirs results in a number of physical mechanisms that help in mobilizing and extracting the oil. Depending on the pressure, temperature, and the compositions of reservoir oil and the injected gas, immiscible or miscible displacements occur. The mobility ratio of displacing to displaced fluids and the gravity and capillary forces determine the extent of viscous fingering that would take place in a gas displacement process. Often the mass transport is affected by dispersion in different directions due to varying velocity gradients. The oil recovery in a miscible displacement process depends on the size of the mixing zone between the injected fluid and the reservoir oil. For maximum oil recovery at breakthrough to occur, the mixing zone should remain small compared to the reservoir volume so that the oil produced is not diluted by the injected fluid. Ideally in a reservoir with a small mixing zone, for complete oil recovery, slightly more than one reservoir pore volume of injection fluid is required. However, if the mixing zone is large, several reservoir pore volumes of injection fluid may be needed to achieve complete recovery(1). On the other hand, the mixing due to diffusion and dispersion can dampen out viscous fingers in an unstable displacement, leading to increased sweep efficiency. Dispersive mixing is caused by molecular diffusion and mechanical dispersion and is the main part of the mixing in miscible displacements(2). Molecular diffusion is a phenomenon whereby the transport of mass of a species (component) occurs within a single fluid phase from one point to the other in the direction of decreasing concentration.

Multiresolution Wavelet Scale Up of Unstable Miscible Displacements in Flow Through Heterogeneous Porous Media

We describe scale up of geological models of field-scale porous media using a new method based on the wavelet transformations. The porous media of interest contain broadly-distributed and correlated permeabilities. Wavelet transformation of the permeability field of such porous media coarsens the geological model from smallest to largest length scales, drastically reduces the number of equations to be solved, preserves the important information on the permeability field at all the relevant length scales, and yields numerical results for any fluid flow property that are as accurate as those that are obtained with the highly detailed geological model of the same porous media. To test this method, we carry out extensive computer simulations of unstable miscible displacement processes and the associated viscous fingering phenomenon in highly heterogeneous porous media, both with the fine-scale geological model and the coarsened model. Excellent agreement is found between the results of the two sets of simulations.

Modeling of Both Near-Wellbore Damage and Natural Cleanup of Horizontal Wells Drilled With Water-Based Drilling Fluids

Summary Prediction of formation damage that occurs in horizontal wells, often openhole completed, is a critical point for optimizing an oilfield development. The economic impact of near-wellbore induced drilling damage and cleanup efficiency has led to significant progress in both experimental and numerical studies designed to assess the wellbore flow properties during oil production. In a previous paper, a methodology combining both experimental and numerical approaches was presented to evaluate the natural cleanup of horizontal wells drilled with an oil-based mud (OBM). This paper presents an extension of the methodology for simulating both (a) near-wellbore invasion and permeability damage generated with a water-based mud (WBM), and (b) natural cleanup during oil backflow when the well is put into production. There is a fundamental difference between WBM and OBM invasions. In an oil-bearing formation, the displacement of the oil in place with an OBM filtrate is a miscible displacement process, while the displacement with a WBM filtrate is a two-phase flow process (imbibition), generating high wetting-phase saturation in the invaded zone. Then, during oil backflow, a portion of the wetting phase is trapped, leading to residual wetting-phase saturation greater than the initial one. Even in the absence of chemical interaction between filtrate and fluids in place, this induces an adverse water/oil relative permeability effect, which is an additional permeability impairment. This paper describes a numerical approach to model the formation damage with WBM and to predict well performance for natural cleanup when the well is subject to a pressure drawdown. The kinetics of fluid filtrate invasion, the filter-cake properties, and the filtrate/oil relative permeability curves in imbibition and drainage, together with damaged and return permeabilities, are obtained from specific drilling fluid damage laboratory tests. Using these data, the fluid filtrate invasion during the drilling phase is simulated, leading to a cone-type invasion depth along the horizontal well. This approach has allowed us to study the impact of various parameters related to fluids or cake properties, drilling conditions, and natural cleanup processes on the well performance.

イラン産天然フラクチャーコアを使ったミシブル置換効果の実験的検証

Determining the feasibility of miscible displacement process to increase oil recovery from Iranian naturally fractured reservoirs is the subject of this study. For that purpose, miscible displacement experiments including liquefied petroleum gas (LPG) injection were carried out under reservoir conditions on composite cores, consisting of reservoir fractured core plugs of the chosen rock type. Results of experimental studies indicated that LPG miscible flooding could maximize oil recovery. In this paper, results of the Iranian fractured core flooding experiments are presented.

Development of a Statistical Predictive Model for Solvent-Aided Waterflooding

Various studies have shown that miscible displacement by alternating the injection of hydrocarbon solvent and water recovers more residual oil than either solvent injection or waterflooding alone. However, economic considerations have limited the amount of solvent that could be injected during the miscible displacement process and has constrained its application for maximum oil recovery. Statistical modeling techniques were used to analyze various field and laboratory studies in which miscible displacement by hydrocarbon solvent and injected water were implemented. This provided an avenue to describe the performance of solvent-aided-waterflooding displacement and effect of various parameters on this process. The amount of hydrocarbon solvent, ratio of injected water to solvent and formation thickness were incorporated in the model to establish their relationship with incremental oil recovery. Multiple regression analysis was used to develop the model and the result indicated that future performance of the solvent-aided-waterflooding displacement process could be predicted effectively.

Stability of Polymerizing Liquid Flow in Porous Media

ABSTRACTThis paper examines the flow stability of a polymerizing liquid in an anisotropic porous medium. The polymerization reaction leads to an increasing viscosity along the flow direction, particularly behind the advancing resin/air front, and may cause the miscible displacement process to become unstable and uneven. A linearized stability analysis of the flow within the filled region behind the liquid / air interface has been conducted. This reveals that under a moderate adverse viscosity gradient, the polymerization reaction has the potential for stabilizing the flow process by damping out disturbances of wavelengths above a critical size. Guidelines are provided for adjusting the composition of the reacting liquid and the anisotropic medium permeability to stabilize the flow process.