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Results
Abstract Many light and medium gravity oil reservoirs have an underlying contiguous water zone, in communication with the oil zone. As a result, a conventional waterflood is often unsuccessful because the injected water tends to channel into the more conductive bottom water layer. The research results discussed here show that modified waterfloods of such reservoirs may still be economically viable. Experiments were carried out in a three-dimensional model, employing a number of techniques, including horizontal wells. The flooding fluids consisted of polymer solutions and emulsions. The most successful strategy was to use a 10% quality oilin- water emulsion as a blocking agent, and a polymer solution as the mobility control fluid. Such a combination yielded oil recoveries approaching 70%, as compared to 50% for a conventional waterflood, for equally thick oil and water layers. The experimental results were correlated by means of a threezone analytical model allowing for crossflow between oil and water layers, which is useful for predicting the performance of such floods. Experiments utilizing horizontal injector-producer pairs for conventional waterfloods in the presence of a water leg, as well as floods utilizing polymers and emulsions showed only limited gains over vertical well pairs. Guidelines are offered for the choice of well and fluid combinations for successful floods. Introduction Waterflooding is a relatively inexpensive secondary recovery method that is used widely in the petroleum industry. In the provinces of Alberta and Saskatchewan a number of light and moderately heavy oil reservoirs contain a high water saturation zone in communication with the oil zone. Under conventional waterflood such reservoirs have been observed to show poor performance. The major reason for this is an insufficient and incomplete sweep of the reservoir by the injected water, which tends to move to the producing wells through the more permeable portions of the reservoir. This results in low recovery. Several laboratory model studies have been undertaken to investigate the effect of various parameters on oil recovery in bottom water reservoirs. High water cuts and rapidly decreasing oil rates early in the production life of such reservoirs have, in many instances, prompted their suspension or abandonment at very low levels of recovery. Mobility ratio is perhaps the single most important parameter in waterflooding bottom water reservoirs. A number of flooding fluids have been used to control mobility ratio. This paper examines effective techniques to waterflood bottom water reservoirs using polymer and emulsion as mobility control and/or blocking agents. The effect of vertical and horizontal injectors and different combinations were also investigated. Experimental Set-up and Procedure A diagram of the experimental apparatus is shown in Figure 1. The apparatus is made up of two constant rate pumps and a specially- designed aluminum core holder with a rectangular crosssection. The inside dimensions of the core holder were 5.08 cm (2.0 in.) wide, 7.62 cm (3.0 in.) deep and 122 cm (48 in.) long. Two pumps were used for simultaneous injection of two different fluids to simulate a vertical displacement front. The injection well was specially designed to allow the simultaneous injection of two different fluids.
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.82)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.54)
Abstract Emulsions play more and more important role in the oil recovery as they are found to occur in most enhanced oil recovery processes and are involved in certain modes of crude oil transportation. Furthermore, they can also be used in secondary recovery as blocking agents to improve waterflooding performance in layered reservoirs or under bottom-water conditions. However, there is still a lack of detailed understanding of the mechanisms involved during the displacement process. Therefore, there is a need for understanding the physics controlling the flow of an emulsion in a porous medium. However, very little research has been carried out in the area of the flow mechanics of emulsions in porous media. Additionally, emulsion rheology and drop capture were investigated separately for certain conditions. These conditions restrict the model to specific applications. This leads to the question of how emulsion transport occurs in a porous medium in the case where emulsion drop size and the pore size are comparable, which is often the case. Therefore, the present study was carried out to observe the physical mechanisms that occurred when a stable emulsion flows in a porous medium for the system of comparable drop and pore sizes. Particularly, emulsion rheologies and droplet captures for both caustic and surfactant emulsions flowing through Berea sandstone and Ottawa sand packs were investigated comprehensively. The results show that the change in emulsion rheology in a porous medium has an overall trend similar to that in a viscometer for the shear rates of interest. Furthermore, the emulsion droplets were found to be captured according to a filtration process. P. 657
- North America > Canada > Alberta (0.29)
- North America > United States > California (0.28)
- North America > United States > West Virginia (0.27)
- (3 more...)
- Research Report > New Finding (0.68)
- Research Report > Experimental Study (0.68)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Downhole chemical treatments and fluid compatibility (0.95)
Abstract The importance and application of emulsions in the oil recovery has received considerable attention; for example, emulsion flooding which is a complex EOR process involving several mechanisms that occur at the same time during displacement. Therefore, to simulate oil recovery by emulsion flooding requires an understanding of the flow mechanics of emulsions in porous media. With this end in view, the present study was carried out to achieve a better mechanistic understanding of emulsion flow and its mathematical representation. Particularly, emulsion rheology and droplet capture for the system of comparable drop and pore sizes were investigated comprehensively. These mechanisms, namely emulsion rheology, droplet capture, and surfactant adsorption, were then represented mathematically and incorporated into a one-dimensional, three phase (oleic, aqueous, and emulsion) mathematical model which accounted for interactions of surfactant, oil, water, and the rock matrix. The simulator was validated by comparing the simulation results with the results from linear core floods performed in the laboratory. The comparison was made using different physical property models and testing various mechanisms to determine which combination best followed the core flood observations and measurements. It was found that a multiphase non-Newtonian rheological model of an emulsion with interfacial tension-dependent relative permeabilities and time-dependent capture gave the best match of the experimental core floods. A sensitivity study of the injection pressure and cumulative oleic recovery was also carried out to determine the effect of the process variables on the model predictions. Introduction Since emulsions play an important role in many EOR processes, attempts have been made to simulate these processes with increasingly complex compositional simulators. These require a detailed understanding of the mechanisms involved during the displacement process. Therefore, there is a need to understand the physics controlling the flow of an emulsion in a porous medium. However, very little research has been carried out in the area of the flow mechanics of emulsions in porous media. Additionally, emulsion rheology and drop capture have been investigated separately for certain conditions. These conditions restrict the model to specific applications. This leads to the question of how emulsion transport occurs in a porous medium in the case where emulsion drop size and the pore size are comparable, which is often the case. Therefore, the present study investigates these subjects to achieve a better mechanistic understanding of emulsion flow and its mathematical representation. This will provide information that can be applied in any EOR process involving emulsion flow. Experimental Work Physical Mechanism Observations. A number of experimental core floods were conducted in this study to observe the physical mechanisms that occurred during stable emulsion flow in a porous medium. These are described in Ref. 1. The observations found from this study can be summarized as follows:Observations were made of the rheological behaviour of the caustic and surfactant emulsions for the system of comparable drop to pore size for both Berea sandstones and Ottawa sand packs. Rheological similarities were seen when the emulsions flowed in porous media and in a viscometer with slight differences probably due to an interaction between drops and pores. The above finding of the emulsion rheology was drawn from the comparison of the rheological behaviour of emulsion flow in a porous medium with the rheological behaviour of an injected emulsion as measured by a viscometer.
- North America > United States > Pennsylvania (0.48)
- North America > Canada > Alberta (0.47)
Abstract The importance and application of emulsions in the oil recovery has received considerable attention. This is a first attempt to simulate macro emulsion flooding performance compositionally by including the physical property changes that occur simultaneously during multiphase displacement. Since emulsion flooding is a complex EOR process involving several mechanisms that occur at the same time during displacement, simulation of oil recovery by emulsion flooding requires an understanding of the flow mechanics of emulsions in porous media. With this end in view, the present study was carried out to achieve a better mechanistic understanding of emulsion flow and its mathematical representation. In the first phase of this research, the physical mechanisms were observed during stable emulsion flow in a porous medium. Particularly, emulsion rheology and droplet capture for the system of comparable drop and pore sizes were investigated comprehensively. These mechanisms, namely emulsion rheology, droplet capture, and surfactant adsorption, were then represented mathematically and incorporated into a one-dimensional, three-phase (oleic, aqueous, and emulsion) mathematical model which accounted for interactions of surfactant, oil, water, and the rock matrix. The simulator was validated by comparing the simulation results with the results from linear core floods performed in the laboratory. The comparison was made using different physical property models and testing various mechanisms to determine which combination best followed the core flood observations and measurements. It was found that a multiphase non-Newtonian rheological model of an emulsion with interfacial tension-dependent relative permeabilities and time-dependent capture gave the best match of the experimental corefloods. Introduction Since emulsions play an important role in many EOR processes, attempts have been made to simulate these processes with increasingly complex compositional simulators. These require a detailed understanding of the mechanisms involved during the displacement process. Therefore, there is a need to understand the physics controlling the flow of an emulsion in a porous medium. However, very little research has been carried out in the area of the flow mechanics of emulsions in porous media. Additionally, emulsion rheology and drop capture have been investigated separately for certain conditions. These conditions restrict the model to specific applications. This leads to the question of how emulsion transport occurs in a porous medium in the case where emulsion drop size and the pore size are comparable, which is often the case. Therefore, the present study investigates these subjects to achieve a better mechanistic understanding of emulsion flow and its mathematical representation. This will provide information that can be applied in any EOR process involving emulsion flow. EXPERIMENTAL WORK Physical Mechanism Observations A number of experimental core floods were conducted in this study to observe the physical mechanisms that occurred during stable emulsion flow in a porous medium. These are described in Ref. 1. The observations found from this study can be summarized as follows:Observations were made of the rheological behavior of the caustic and surfactant emulsions for the system of comparable drop to pore size for both Berea sandstones and Ottawa sand packs. Rheological similarities were seen when the emulsions flowed in porous media and in a viscometer with slight differences probably due to an interaction between drops and pores.
- North America > Canada > Alberta (0.31)
- North America > United States > West Virginia (0.25)
- North America > United States > Pennsylvania (0.25)
- (2 more...)
Abstract In many light or moderately viscous oil (1 to 200 mPa.s) reservoirs in Alberta and Saskatchewan, a high water saturation zone of varying thickness and extent, referred to as water leg or bottom water, occurs in communication with the oil zone above. As a result, the primary production period is short, and water coning occurs early (six to 12 months) in the life of the reservoir. Later, during the secondary recovery stage, such a zone can have an adverse effect on the waterflood efficiency. This paper addresses the problem of waterflooding such reservoirs. The presence of a bottom water zone results in poor vertical sweep efficiency due to water channelling through the bottom water zone. A mathematical model was developed to account for cross fIow, and experiments were carried out in a two-dimensional model to test the theory. Many techniques have been proposed to improve waterflood performance in reservoirs under bottom water conditions. Most of these are based upon the use of chemicals to plug the bottom water zone. However, due to crossflow, part of the chemical slug often migrates into the oil zone. Thus, the injection strategy becomes an important factor for maximizing mobility control. A new displacement process, the Dynamic Blocking Process (DBP), was developed which aims at minimizing crossflow between the oil and bottom water lanes. This process is unique in that displacement and blocking processes operate simultaneously. Experimental results showed that DBP yielded approximately 15% higher oil recovery compared to a waterflood conducted after injection of a single emulsion slug into the bottom water zone. Introduction Waterflooding oil reservoirs with a communicating bottom water zone is usually inefficient due to the flood water channeling into the bottom water zone. This problem was first recognized in the early sixties when Barnes suggested the use of a viscous water slug as a mobility control agent to lower the WOR. Since then, the use of various chemicals, such as polymers and emulsions, has been proposed aas mobility control and blocking agents to improve waterflood performance. However, none of these studies accounted for the crossflow between the oil and bottom water layers when planning a chemically augmented waterflood. Other studies have shown that croosflow plays a major role in waterflood performance I layered reservoir. Therefore, it is important to account for the croosflow effect in mobility control in the presence of bottom water. The main objective of his research was to develop mathematical model of crossflow to study water channelling under bottom water conditions. With this model and based on the minimization of crossflow between the oil and bottom water zones, the Dynamic Blocking Process (DBP) is proposed to improve waterflood performance under bottom water conditions. Waterflood experiments were conducted in a model to verify the theory and to study mobility control using emulsions. Derivation of the Crossflow Equation In the following, an attempt is made to develop an expression for crossflow while waterflooding a two-layer reservoir, the lower layer being a water zone.
- North America > Canada > Alberta (0.37)
- North America > Canada > Saskatchewan (0.24)
Modeling of Emulsion Flow In Porous Media
Abou-Kassem, J.H. (UAE University) | Ali, S.M. Farouq (University of Alberta)
Abstract A mathematical description of non-Newtonian fluids, in particular, emulsions, is of special importance now that most of the enhanced oil recovery methods are being modelled in increasing detail. Only recently a few characteristics of emulsion flow have been incorporated in some of the simulators. Nearly all enhanced oil recovery processes involve emulsion formation and flow in some form or other. Representation of such flow in mathematical models is still inadequate. This paper investigates the rheology of emulsions, their formation in porous media, and subsequent flow, from a mathematical standpoint A critical evaluation of several models describing the flow of pseudoplastic fluids in porous media is presented. The models are expressed in a unified form that makes it possible to detect differences between the various models. The assumptions underlying the various models are discussed in detail. Furthermore, the paper gives a summary of the rheology and in situ formation of emulsions, the role of a variety of other factors responsible for emulsification in porous media, and it introduces a flow model for both Newtonian and non-Newtonian emulsions that is practical, and especially suitable for use in numerical simulation of EOR processes. Introduction Two-thirds or the world's crude oil and three-quarters of the U.S. crude oil is produced in an emulsion form. Emulsified oil is produced from oil/tar sands undergoing thermal recovery. New methods of secondary recovery that use high viscosity emulsions have been developed. Filtration of water using porous material also involves dilute concentrations of dispersed oil in water. These factors and others have promoted interest in research related to the now behaviour of non-Newtonian fluids in porous media fur a quarter of a century. The fact that nearly all enhanced oil recovery methods involve emulsion formation and flow coupled with the wide-spread acceptance of reservoir simulation as a valuable tool in the development and optimization of oil recovery from petroleum reservoirs, have contributed to incorporating a few characteristics of emulsion flow in a number of simulators. Mathematical modelling of emulsion flow in porous media calls for the understanding of the rheology of emulsions and the formation of emulsion in oil reservoirs. Emulsion flow in porous media can be modelled through non-Newtonian rheology. as discussed in this paper. A more comprehensive approach would require phase behaviour of the emulsion system and drop size distribution to account for mobility changes in response to drop entrapment. Nature and Rheology of Emulsions An emulsion is a dispersion of one liquid (internal or dispensed phase) with another (external or continuous phase) in the presence of surface -active agents (emulsifiers) . The volume fraction of the dispersed phase is called emulsion quality, θ. The emulsion consists of an oil-soluble portion and water-soluble portion. By virtue of its special structure the emulsifier aids in reducing the interfacial tension between the two liquids involved enabling an easier formation of an extended interface and in preventing the coalescence of the dispersed particles once emulsion is formed. There are two types of emulsion water-in-oil (W/O) and oil-in-water (O/W) emulsions.
- North America > United States (0.25)
- North America > Canada > Alberta (0.16)
Abstract Flow of emulsion in porous media is of great interest to the oil industry because emulsions play an important role in various enhanced oil recovery processes. Even though many laboratory studies have been conducted to understand the rheology of emulsions and mechanisms of emulsion flow through porous media, relatively few efforts have been made towards the mathematical simulation of emulsion rheology and propagation in a porous medium. Only a few researchers have attempted to simulate emulsion flow through porous media, and most of them have considered the case for which emulsion is the only phase present in the system. Besides, mechanisms involved in selectively blocking high-permeability channels have not been incorporated. Also, phenomena of emulsion breaking and formation have been poorly defined by existing flow models. The formulation developed in the present work explains the blocking mechanism of emulsion, incorporates emulsion breaking and formation, and relates emulsion stability and permeability reduction to emulsion throughput and absolute permeability. The mathematical model is tested against experimental results available in the literature, showing excellent agreement. Introduction Emulsion flow in porous media is of interest in almost all enhanced oil recovery (EOR) processes, Emulsions have been used as selectively plugging agents to improve oil recovery in waterflooding as well as chemical and steam-flooding operations. Also, it is believed that emulsion flow occurs by accident in thermal processes (such as in-situ combustion, steam flooding, etc.), chemical flooding, waterflooding or even in primary depletion. Natural porous media often provide enough shear to generate emulsions in-situ. McAuliffe is one of the first researchers to report the use of oil-in-water emulsions in improving oil recovery during water floods. Broz et al. reported laboratory results in the development of emulsion blocking technique for the correction and control of stem override and channeling. While emulsions have been well accepted as effective blocking Agents, very little has been reported on mathematical modeling of emulsion flow through porous media in 1979, Alvarado and Marsden introduced their bulk viscosity model in which an emulsion was considered to be a continuous, single-phase fluid. No permeability reduction was introduced and emulsion flow was different from that described by Darcy's law only when the bulk emulsion viscosity was shear-rate dependent. The so-called ‘droplet retardation model’ was introduced by McAuliffe and was used by Devereux who modified the Buckley-Leverett theory for two-phase flow by including a retardation factor in the pressure driving force of the dispersed oil phase. This model implies that the permeability of the porous medium decreases as emulsion is injected, until steady state is reached. The model also implies that the permeability reduction increases with decreasing flow rate and increasing drop-size to pore-size ratio. One of the problems of this model is that the permeability of the porous media rises back to the initial value when emulsion is followed by water. Soo and Radke presented another mechanism for reducing permeability by emulsion. They argued that, when emulsions are injected into a porous medium, droplets not only block pores of throat sizes smaller than their own but they are captured on pore walls and in crevices forming an ensemble of smaller droplets.
How to Waterflood Reservoirs With a Water Leg
Yeung, K. (University of Alberta) | Ali, S.M. Farouq (University of Alberta)
Abstract Waterflooding oil reservoirs with an underlying water zone is often problematic because the injected water can channel into the water zone, Yet such reservoirs constitute a large resource in Alberta and Saskatchewan. This research was directed toward reducing water mobility in the bottom water zone for more efficient waterflooding. Three novel approaches were tested: the Emulsion Slug Process (ESP), the Alternating Water-emulsion (AWE) Process, and the Dynamic Blocking Procedure (DBP). All three methods result in an improvement in the vertical sweep efficiency and involve the injection of polymer or emulsion, with water. In each case, there are two modes: blocking and displacing. The differences among these processes lie in the application of the two modes. In ESP, the blocking and displacing modes are used only once with the blocking agent injected first, followed by a waterflood. In the AWE process, the two modes are performed alternately. While in DBP, the two modes are performed simultaneously. Experiments conducted in this study showed that by using a suitable mobility control agent in DBP, a noticeable increase in both oil production rate and ultimate oil recovery was realized. The opposite may occur for the wrong choice either of the mobility control agent, or of the approach. The experimental results are presented, with a discussion of the roles of mobility control and blocking agents. Introduction Waterflooding oil reservoirs with a water leg (i.e., a communicating bottom water zone) are usually inefficient due to the flood water channeling into the bottom water zone. This problem was first recognized in the early sixties when Barnes suggested the use of a viscous water slug as a mobility control agent to lower the WOR. Since then, the use of various chemicals such as polymers and emulsions, has been proposed as mobility control and blocking agents to improve waterflood performance. However, none of these studies accounted for crossflow between the oil and bottom water layers when planning a chemical augmented water-flood. Other studies have shown that cross flow plays a major role in waterflood performance in layered reservoirs.Thus, a systematic way of utilizing a chemical or an emulsion as a blocking agent under bottom water conditions accounting for crossflow is required for efficient displacement of oil. In this paper, the Emulsion Slug Process (ESP), the alternating Water-emulsion (AWE) Process, and the Dynamic Blocking Procedure (DBP) are discussed. Emulsion Slug Process (ESP) The main objective of the three processes proposed in this paper is to try to isolate the bottom water zone when displacing oil by water. An emulsion is used as a blocking agent to increase the flow resistance of the bottom water zone. In the Emulsion Slug Process, the blocking mode is performed once at the beginning, followed by a waterflood. Under bottom water conditions, the flow resistance of the oil zone is much higher than that of the bottom water zone, i.e., Ro > > Rw where Ro and Rw are the flow resistances of the oil zone and water leg respectively; thus, the WOR will be high at the beginning of the flood.
- North America > Canada > Alberta (0.36)
- North America > Canada > Saskatchewan (0.25)
Abstract Non-thermal heavy oil recovery methods are important, because many heavy oilreservoirs are unsuited for thermal methods. Emulsion flooding is one of themore promising non-thermal methods. In this experimental research, the effectof injection rate was examined for a Lloydminster crude and for a Morichalcrude oil. Two different emulsions were used, one being oil-in-water and theother one water-inoil-type. Displacement tests were carried out at the reservoir temperature in eachcase. In all tests, the core initially contained irreducible water. Emulsionslugs, 3 and 12% pore volume, were driven by brine. It was found that oil recovery was sensitive to injection rate, insofar asthe recovery varied from 67% to 57% in the case of the Morichal crude, and 59%to 51% in the case of the Lloydmlnster crude, depending on the rate. The floodrate would determine the extent of mobility ratio variation, which in turn, depends on the drop size, the type and rheology of the emulsion. Themechanistic features of the process are discussed. Introduction Considering the large resources of moderately heavy oils that cannot beexploited by thermal methods, it is important that viable non-thermal recoverymethods be developed. At present, at least 10 billion m of oils inthe 100–2000 mPa.s viscosity range occur in reservoirs in Canada, which are toothin, too deep, or marginal for other reasons, and thus unsuitable for theapplication of thermal methods, particularly steam injection. The non-thermalmethods tested In the laboratory and in the field include chemical floods, ofwhich alkaline flooding has received considerable attention. Based uponprevious work, emulsion floods may be more effective than alkaline floods. Theemulsions formed in situ in the latter case must contend with the rock.alkalireactions and the concomitant loss.
- Research Report > New Finding (0.48)
- Research Report > Experimental Study (0.34)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Thermal methods (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Chemical flooding methods (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Oil sand, oil shale, bitumen (0.89)
Abstract This paper presents macroemulsion flooding as all alternative secondary recovery technique for moderately viscous oils in reservoirs unsuitable for thermal recovery applications. In laboratory experiments, wellhead Eyehill crude oil samples were employed directly in the tailoring and systematic development of all emulsion. A unique feature of this research is the use of solvents in adjusting the emulsion characteristics for increased oil displacement efficiency. Emulsion slugs were then injected into partially water flooded cores resulting in incremental recoveries of up to 70%. Introduction This paper deals with designing water-in-oil (W/O) macroemulsions prepared with the Eyehill crude produced in the province of Saskatchewan, and laboratory testing of these emulsions as secondary recovery agents. Previous studies concentrated on the flow properties of macroemulsions in porous media and the emulsions used were oil-in-water (O/W) type. No systematic study of W/O petroleum macroemulsions and their flow properties is known for the present fluid system. Carefully designed crude oil emulsions can offer an alternative recovery technique for heavy oil reservoirs with low primary productivity, poor response to waterflooding and low potential for thermal recovery applications. As reported by Jameson (1973), primary production of a Saskatchewan crude yields between 2% and 8% of the oil-in-place. Because of an adverse mobility ratio, waterflooding is not effective and recovers only an additional 2% to 5% of the oil-in-place. In this study, cost was always kept in perspective because the objective was to formulate a procedure that was simple, effective and practical. Cost was also the reason why sodium hydroxide was preferred to commercial emulsifiers. Wellhead samples of the Eyehill crude oil-water emulsion referred to as "crude" in this paper were used as the basic material in this study. The crude contained already 59% water as dispersed drops. Wellhead crude was thus already a W/O emulsion. The first stage was to examine the parameters affecting interfacial tension. The goal was to determine under what conditions interfacial tension could be lowered sufficiently to obtain homogeneous mixtures. Eyehill crude is an acidic crude containing a wide array of fatty acids which can react with NaOH to give a soap (i.e. surfactant). This, in turn, lowers the interfacial tension and provides the necessary environment for emulsification. The lower the interfacial tension, the smaller the energy required to create new interfaces between the crude and the NaOH solution. The NaOH concentration which provided the lowest interfacial tension was selected. The second stage was to prepare and observe mixtures of Eyehill wellhead crude and of the selected NaOH solution. The goal was to find a mixture that remained homogeneous for a very long period of time. That mixture was then blended with distilled water and/or wellhead crude to determine how well it retained its homogeneity. In the reservoir, an emulsion bank could encounter varying saturations of water and crude. It is important to predict how combinations of these three fluids (i.e. emulsion, distilled water and crude) behaved. If the emulsion broke down, efficiency of displacement would drop. If the viscosity of the emulsion increased drastically, the porous medium would become plugged.