Solvent and Driving Gas Compositions for Miscible Slug Displacement

1970 ◽  
Vol 10 (03) ◽  
pp. 298-310 ◽  
Author(s):  
Lyman Yarborough ◽  
L.R. Smith
Keyword(s):  
Crude Oil ◽  
Phase Behavior ◽  
Nitrogen Concentration ◽  
Equilibrium Phase ◽  
Miscible Displacement ◽  
Limiting Factor ◽  
Liquefied Petroleum Gas ◽  
Contact Zones ◽  
Wide Range ◽  
Gas Drive

Abstract Experimental data were used for determining miscibility in liquefied petroleum gas (LPG) slug flooding and enriched gas drive of crude oils. The miscibility data for LPG slug flooding includes cases where the driving gas contains large amounts of nitrogen and when low pressure miscible displacement is desired. The results of flow tests for enriched gases miscibly displacing crude oil are given. These data cover a wide range of reservoir oil properties and miscibility pressures. Methods for predicting compositional requirements for both miscible slug displacement processes are recommended and should be useful for preliminary engineering evaluation of miscible slug displacement for a reservoir. Introduction The two most frequently applied hydrocarbon solvent processes for miscible displacement of crude oil are liquefied petroleum gas (LPG) slug flooding and enriched gas drive. A slug of the LPG or enriched gas is injected and followed by dry gas or gas-water displacement. In both cases the injected material forms a miscible slug in the reservoir. Generally, there are two fluid contact zones in which the establishment of miscibility must be considered as related to the fluid compositions and the reservoir temperature and pressure. The first zone is the solvent-reservoir oil pressure. The first zone is the solvent-reservoir oil contact zone; the second zone is where the lean scavenging gas and solvent come together. For successful miscible displacement, there must be single-hydrocarbon-phase condition throughout both contact zones. Aside from possible repressuring procedures which may be undertaken prior to solvent procedures which may be undertaken prior to solvent injection, the primary engineering control for achieving miscibility is the proper specification of the solvent and driving gas compositions. This paper discusses the compositional requirements for paper discusses the compositional requirements for miscibility to be achieved in both contact zones and considers cases where the reservoir pressure is very low or the driving gas contains a large amount of nitrogen. LPG SLUG FLOODING FOR MISCIBLE DISPLACEMENT OF CRUDE OIL In LPG slug flooding there is no problem in achieving miscibility with the crude oil under conditions where the solvent remains liquid. Miscibility between the LPG slug and the driving gas may be the limiting factor. At pressures below 1,100 to 1,200 psia, miscibility often cannot be achieved between the LPG and driving gas, and even higher pressures may be required if the available driving gas contains an appreciable concentration of nitrogen. Another area of increasing interest is LPG slug flooding in reservoirs where the pressure is 1,000 psia or below. At these pressures the methane-LPG transition cannot be pressures the methane-LPG transition cannot be single phase at temperatures below 160 degrees F. The only practicable approach to achieving miscible displacement under these conditions is to inject an ethane-rich buffer slug between the LPG and the driving gas. To determine the allowable nitrogen concentration for gases driving LPG, the phase behavior of nitrogen-methane-propane mixtures was experimentally studied at 105 degrees and 120 degrees F. Similarly, equilibrium-phase behavior data were obtained for the methane-ethane-propane system at 105 degrees F. The latter results allow estimates to be made of the buffer-slug composition necessary for miscible displacement at low pressures. Also, the effects of small amounts of butane and pentane on the phase behavior of the nitrogen-methane-propane and the nitrogen-methane-ethane-propane system were studied. SPEJ p. 278

Surfactant Retention in Berea Sandstone- Effects of Phase Behavior and Temperature

1982 ◽  
Vol 22 (06) ◽  
pp. 962-970 ◽  
Author(s):  
J. Novosad
Keyword(s):  
Porous Media ◽  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Liquid Interface ◽  
Divalent Ions ◽  
Surfactant Precipitation ◽  
Wide Range ◽  
Solid Liquid Interface ◽  
Solid Liquid

Novosad, J., SPE, Petroleum Recovery Inst. Abstract Experimental procedures designed to differentiate between surfactant retained in porous media because of adsorption and surfactant retained because Of unfavorable phase behavior are developed and tested with three types of surfactants. Several series of experiments with systematic changes in one variable such as surfactant/cosurfactant ratio, slug size, or temperature are performed, and overall surfactant retention then is interpreted in terms of adsorption and losses caused by unfavorable phase behavior. Introduction Adsorption of surfactants considered for enhanced oil recovery (EOR) applications has been studied extensively in the last few years since it has been shown that it is possible to develop surfactant systems that displace oil from porous media almost completely when used in large quantities. Effective oil recovery by surfactants is not a question of principle but rather a question of economics. Since surfactants are more expensive than crude oil, development of a practical EOR technology depends on how much surfactant can be sacrificed economically while recovering additional crude oil from a reservoir.It was recognized earlier that adsorption may be only one of a number of factors that contribute to total surfactant retention. Other mechanisms may include surfactant entrapment in an immobile oil phase surfactant precipitation by divalent ions, surfactant precipitation caused by a separation of the cosurfactant from the surfactant, and surfactant precipitation resulting from chromatographic separation of different surfactant specks. The principal objective of this work is to evaluate the experimental techniques that can be used for measuring surfactant adsorption and to study experimentally two mechanisms responsible for surfactant retention. Specifically, we try to differentiate between the adsorption of surfactants at the solid/liquid interface and the retention of the surfactants because of trapping in the immobile hydrocarbon phase that remains within the core following a surfactant flood. Measurement of Adsorption at the Solid/Liquid Interface Previous adsorption measurements of surfactants considered for EOR produced adsorption isotherms of unusual shapes and unexpected features. Primarily, an adsorption maximum was observed when total surfactant retention was plotted against the concentration of injected surfactant. Numerous explanations have been offered for these peaks, such as a formation of mixed micelles, the effects of structure-forming and structurebreaking cations, and the precipitation and consequent redissolution of divalent ions. It is difficult to assess which of these effects is responsible for the peaks in a particular situation and their relative importance. However, in view of the number of physicochemical processes taking place simultaneously and the large number of components present in most systems, it seems that we should not expect smooth monotonically increasing isotherms patterned after adsorption isothemes obtained with one pure component and a solvent. Also, it should be realized that most experimental procedures do not yield an amount of surfactant adsorbed but rather a measure of the surface excess.An adsorption isotherm, expressed in terms of the surface excess as a function of an equilibrium surfactant concentration, by definition must contain a maximum if the data are measured over a sufficiently wide range of concentrations. SPEJ P. 962^

Prediction of the Phase Behavior Generated by the Enriched-Gas-Drive Process

1965 ◽  
Vol 5 (02) ◽  
pp. 160-166 ◽  
Author(s):  
A.M. Rowe ◽  
I.H. Silberberg
Keyword(s):  
Computer Program ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Miscible Displacement ◽  
Phase Changes ◽  
Experimental Results ◽  
High Concentration ◽  
Gas Drive ◽  
Non Equilibrium ◽  
Vapor Liquid

Abstract A computer program was written to predict the phase behavior generated by the enriched-gas-drive process. This program is based, in part, on a new concept of convergence pressure, which is then used to select vapor-liquid equilibrium ratios (K-factors) for performing a series of flash calculations. The results of these calculations are the equilibrium vapor and liquid phase compositions which define the phase envelopes. The program was used to predict phase envelopes for 11 different hydrocarbon systems on which published experimental data were available. The predicted and experimental results compare favorably. Introduction The reservoir engineer is frequently faced with the problem of predicting what will happen if gas is injected into a reservoir. One aspect of this general problem is predicting the phase changes that will occur when a non-equilibrium gas displaces a reservoir fluid. In particular, a "dry" gas, upon displacing a volatile oil will pick up intermediate components from the oil. On the other hand, a "wet" gas, containing a high concentration of intermediates, will lose some of these components to a relatively low-gravity, non-equilibrium crude. It is this latter process, occurring in the enriched-gas displacement, which is treated in this paper. In the past, these phase changes have been determined experimentally and the results incorporated into various modifications of the Buckley-Leverett analysis. Such experimental work is time consuming, and the results are sensitive to numerous experimental errors. With the wide availability of high-speed digital computing equipment and numerous correlations pertaining to the vapor-liquid equilibria of hydrocarbon systems, it is now practical to calculate such phase behavior. This paper describes a computer program for performing these calculations. THE ENRICHED GAS DISPLACEMENT PROCESS Experimental results have shown that oil recovery can be significantly increased by enriching the displacing gas with intermediate hydrocarbon components. The essential features of the phase behavior generated by this enriched-gas-drive process are commonly illustrated with ternary diagrams such as Fig. 1. In this figure, Gas D, which contains a high concentration of intermediate hydrocarbons with respect to the undersaturated Crude A, is injected into the reservoir. When D contacts A, gas goes into solution until the oil becomes saturated (Point. B). Further contacting of Gas D and saturated Oil B results in a Mixture C which separates into Vapor Y(c) and Liquid X(c). Liquid X(c) is contacted by additional Gas D, resulting in Mixture E which separates into Vapor Y(e) and Liquid X(e). Repeated contacts of the liquid by the injected gas will eventually result in Liquid X(d) of maximum enrichment existing in equilibrium with Gas Y(d). The equilibrium tie-line X(d) Y(d), when extended, passes through the Point D representing the enriched injection gas. For systems of more than three components, the predicted equilibrium states are dependent upon not only reservoir temperature and pressure, but also the compositions of the crude oil and injected gas. If the gas is sufficiently enriched, a miscible displacement is generated. Line is tangent to the phase envelope at the critical point (Point Z) and represents the limiting slope of the tie-lines as the critical state is approached. Point I therefore represents the minimum enrichment of injection gas required to generate a miscible displacement. Point G represents the minimum enrichment required for initial miscibility of the injection gas with Crude A.Attra has presented a method to be used for prediction of oil recovery by the enriched gas displacement process. To develop the phase behavior data needed, he designed the experimental procedure described in the following quotation from his paper SPEJ P. 160ˆ

Thermodynamic Modeling of Phase and Tension Behavior of CO2/Hydrocarbon Systems

1985 ◽  
Vol 25 (02) ◽  
pp. 235-254 ◽  
Author(s):  
Muhammad Sahimi ◽  
H. Ted Davis ◽  
L.E. Scriven
Keyword(s):  
Phase Equilibria ◽  
Crude Oil ◽  
Phase Behavior ◽  
Gradient Theory ◽  
Homogeneous Fluid ◽  
Liquid Liquid Extraction ◽  
Interfacial Composition ◽  
Composition Profiles ◽  
Gas Drive ◽  
Liquid Vapor

Abstract The gradient theory of in homogeneous fluid is used to predict phase splits and compositions, interfacial composition profiles, and interfacial tension (IFT) of liquid-liquid, liquid-vapor, and liquid-liquid-vapor equilibria in binary and ternary mixtures of CO2 with propane and decane. The theory's input are the equation of state (EOS) of homogeneous fluid and the influence parameters of inhomogeneous fluid. An efficient computational algorithm is presented for simultaneously generating phase behavior, critical points, interfacial composition profiles, and tension between the phases. Most calculations are made with the Peng-Robinson EOS and the geometric mixing rule for the influence parameters. Use of other EOS and alternative schemes for choosing the influence parameters is explored. Introduction CO2 is a promising agent for enhancing petroleum recovery. Laboratory and field studies have established that CO2 can be an efficient oil-displacing agent. The various mechanisms by which it can act includesolution gas drive,immiscible CO2 drive,hydrocarbon/CO2 miscible drive,hydrocarbon vaporization,direct miscible CO2 drive, andmulticontact dynamic miscible drive. Phase-equilibria a data for CO2-reservoir oils have been reported. The data suggest that two distinct types of equilibria are possible. In one, there are only two phases, liquid and vapor. In the other, there is a region of liquid-vapor equilibrium, but in the phase diagram it exists in conjunction with both liquid-liquid and liquid-liquid-vapor regions. Hutchinson and Braun have shown how a lean gas can develop miscibility with a relatively rich oil. Miscibility is achieved when the lean gas strips intermediates from the liquid until the gas composition is rich enough to be miscible with the original oil. This process is called the high-pressure or vaporizing gas drive. In CO2/crude-oil systems of only one liquid phase and one vapor phase, the miscibility development mechanism can be regarded as vaporization. If the temperature is relatively low, the mechanism is described more accurately as condensation (absorption) of CO2 into the oil phase. In CO2/crude-oil systems that display more than one liquid phase in conjunction with a vapor phase, the mechanism is one of condensation and can account for a phenomenon reported by Shelton and Yarborough, namely that two liquid phases card form either with or without vapor being present. The displacement then has the appearance of a liquid-liquid extraction process. In any case, the miscibility development mechanism is related directly to the phase equilibria of the CO2/reservoir-fluid system. All these mechanisms are characterized by high recoveries in the laboratory. Simon et al. suggested that IFT effects are responsible for high recoveries in a vaporizing situation and might be equally effective in a liquid-liquid extraction situation; consequently, it is desirable to study tension behavior along with the phase behavior of CO2/hydrocarbon systems, as we do here. We make use of a molecular theory, the gradient theory of inhomogeneous fluid, which unifies phase and tension behavior in a practicable way. Such an approach has not been followed before. The CO2/propane (C3) / decane (C1O) system was selected for this study because CO2-C3 and CO2-C1O binary phase equilibria data for wide ranges of temperature and pressure are available. Propane represents the light ends and decane the heavier components. Of course, CO2 and reservoir oils do not have exactly the same phase (and therefore tension) behavior as the simple binary and ternary systems discussed here, but as Hutchinson and Braun demonstrated, these systems can give at least a qualitative description of the phase behavior of CO2/crude-oil systems, although Rathmell et al. indicated that when large amounts of CO2 and methane (C1) are both present, a quaternary diagram is needed to account for the observed behavior. Phase Behavior Calculations The design of a CO2 flooding process requires accurate phase behavior predictions of the equilibrium between the oil in place and the injected CO2. In one approach, the experimental data and extrapolations or interpolations are used in the process simulator. This approach can be quite inaccurate unless a great deal of data are available. Alternatively, an EOS can be postulated and its adjustable parameters fit to a limited amount of data. This is clearly the best approach when a good EOS can be found. As shown in the next section, it is the only feasible approach when IFT are to be predicted along with phase behavior. SPEJ P. 235^

Research of Phase Behavior in Natural Gas Drive Process and Its Application in T_D Reservoir with HTHP

2021 ◽  
Author(s):  
Tongwen Jiang ◽  
Daiyu ZHOU ◽  
Liming LIAN ◽  
Yiming WU ◽  
Zangyuan WU ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Natural Gas ◽  
Crude Oil ◽  
Phase Behavior ◽  
Viscosity Reduction ◽  
Solid Point ◽  
Displacement Efficiency ◽  
Laser Method ◽  
Gas Drive ◽  
Solid Deposition

Abstract Different from other gas drive processes, phase behavior performs more significant roles in natural gas drive process. The main reason is that more severe mass transfer effect and similar phase solubility effect have been caused by multicomponent interaction. This paper provides a series of methods to study the phase behavior in natural gas drive process, aiming to reveal further mechanism and give technical supports to the on-site practice in T_D Reservoir with HTHP. Four key parameters of natural gas drive have been determined. Firstly, laboratory compounding method has been improved to obtain real components of formation fluids and actual injected gas at formation condition (140°C, 45MPa). Secondly, 19 sets of slim tube test has been carried to determine MMP (minimum miscible pressure) and the injected gas components ensuring miscibility. Thirdly, swelling test and laser method have been used to separately obtain the viscosity reduction degree and solid deposition effects. Finally, multiple contact test has been carried to describe the miscibility behavior. All the above have been applied in T_D Reservoir. Conclusions could be drawn from the results obtained by the methods above. Firstly, swelling capacity of crude oil could be enhanced by natural gas for the formation volume factor of crude oil in T_D Reservoir increased by 57% and the viscosity decreased by 83% after natural gas injection. Secondly, MMP of dry gas and crude oil in T_D Reservoir is 43.5MPa with a miscible displacement efficiency above 90% (>30% compared with immiscible displacement efficiency), and the content of N2+C1 should be controlled over 88%. Thirdly, results of 5 levels contact experiments shows that miscibility behavior of natural gas and oil from T_D Reservoir performs an evaporative-condensate composite miscible process in which the condensate miscible process takes the lead. Finally, obvious solid point has not been observed in natural gas drive process of crude oil from T_D Reservoir at the formation temperature, and the effect of solid deposition on the fluid flow in formation could be ignored because of trace amount of solid solution (<1mg/ml) and minute formation permeability damage (<8%). The achievements above have been applied in T_D Reservoir as one of the important technical means supporting over 350,000 tons increased production by natural gas drive. A systematic methods have been reorganized to research the phase behavior in natural gas drive process and half of these methods mentioned above get partially improvement. These physical simulation experiments have covered most mainly processes and the key parameters in reservoirs with HTHP and natural gas drive, including mass transfer, viscosity, expansion, volume coefficient, MMP, miscibility behavior and solid deposition. Every experiment gives a quantitative analysis which possesses satisfied practicability in field application.

Equilibrium Phase Compositions of CO2/Hydrocarbon Mixtures Part 1: Measurement by a Continuous Multiple-Contact Experiment

1983 ◽  
Vol 23 (02) ◽  
pp. 272-280 ◽  
Author(s):  
Franklin M. Orr ◽  
Matthew K. Silva
Keyword(s):  
Phase Composition ◽  
Crude Oil ◽  
Phase Behavior ◽  
Experimental Technique ◽  
Equilibrium Phase ◽  
Static Equilibrium ◽  
Volumetric Data ◽  
Composition Data ◽  
Fluid Properties ◽  
Rigorous Test

Abstract A new experimental technique that simultaneously measures compositions and densities of two phases in equilibrium is described. Because it operates continuously, the experiment can be performed more rapidly than conventional static-equilibrium measurements. Details of the experimental apparatus are reported, and results of test displacements for two simple CO2/hydrocarbon systems are compared with static-equilibrium phase composition measurements for the same systems. A simple analysis of the operation of the experiment is used to assess the experimental error that results from the continuous nature of the experiment and to suggest ways to reduce that error. Application of the experimental technique to a CO2/crude oil system is reported in a companion paper. Introduction It is by now well documented that phase behavior of CO2/crude oil mixtures has an important impact on CO2-flood-displacement efficiency. As a result, a variety of reservoir simulators applicable to CO2 flooding attempt to calculate compositions and fluid properties of phases that occur during the displacement process. However, the equations of state (EOS) or K-value correlations used to calculate the distribution of components between phases in those simulators often do not yield predictions accurate enough phases in those simulators often do not yield predictions accurate enough to be used without some experimental verification. The correlation parameters that describe the pseudocomponents used to represent the crude parameters that describe the pseudocomponents used to represent the crude oil are rarely known well enough to guarantee accurate a priori predictions. Usually, some sort of adjustment of input parameters is predictions. Usually, some sort of adjustment of input parameters is required to achieve an acceptable match of experimental phase-behavior data. Volumetric data, obtained from observations in a visual cell of binary mixtures of CO2 with crude oil at various pressures, are often used to make that adjustment. A few investigators have also reported measurements of phase compositions, though problems with sampling and analysis of high-pressure mixtures make such experiments difficult to perform. Phase-composition data provide a more rigorous test of the perform. Phase-composition data provide a more rigorous test of the predictions of a phase-behavior calculation than volumetric data and hence predictions of a phase-behavior calculation than volumetric data and hence are desirable. In addition, simultaneous fluid property data would be useful for testing predictions of phase densities and viscosities and for direct application in design of some processes--for instance, those that rely on gravity segregation to reduce the adverse impact of viscous instabilities. Unfortunately, published examples of simultaneous measurements of phase compositions and fluid properties are rare. The time and equipment required to make the mixtures, obtain samples and analyze them, and finally determine their viscosities and densities are sufficient to make such measurements unattractive for routine support of field projects. projects. SPEJ p. 272

scholarly journals Phase behavior and miscible mechanism in the displacement of crude oil with associated sour gas

2019 ◽  
Vol 74 ◽  
pp. 54 ◽  
Author(s):  
Congge He ◽  
Longxin Mu ◽  
Anzhu Xu ◽  
Lun Zhao ◽  
Jun He ◽  
...  
Keyword(s):  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Drive Mechanism ◽  
Investment Cost ◽  
Compositional Simulator ◽  
Point Pressure ◽  
Gas Drive ◽  
Effective Development ◽  
Sour Gas

The re-injection of associated sour gas, with high H2S and CO2 content, into the reservoir is proposed to be an effective development method due to its low investment cost and high oil recovery. The aim of this work is to present the phase behavior and miscible mechanism of crude oil displaced by associated sour gas. Based on the equation of state and the phase equilibrium theory, the phase behavior of crude oil mixed with various gases (associated sour gas, H2S, CO2 and CH4) have been analyzed. Then, the miscibility of associated sour gas was determined by calculating its Minimum Miscible Pressure (MMP) and the effect of sour component fraction on miscibility was evaluated. Moreover, a series of numerical simulations modeling 1D slim-tube were conducted using a compositional simulator to study the miscible mechanism in the displacement of crude oil with associated sour gas. The results show that the injection of H2S can reduce the bubble point pressure of crude oil and therefore is beneficial to prevent the crude oil degassing; nevertheless, the injection of CO2 has little effect on it. The miscible ability of associated sour gas decreases as its sour component fraction decreases. It is observed that the crude oil displaced by associated sour gas and sweet gas both show a combined condensing/vaporizing mechanism, with miscible zone in the middle of transition zone. However, the vaporizing-gas drive mechanism is slightly stronger than the condensing-gas drive mechanism during the displacement by associated sour gas while is significantly stronger during the displacement by sweet gas.

Using Phase surfaces to Describe Condensing-Gas-Drive Experiments

1965 ◽  
Vol 5 (03) ◽  
pp. 184-185
Author(s):  
Fred I. Stalkup
Keyword(s):  
Phase Behavior ◽  
Miscible Displacement ◽  
Ternary Diagram ◽  
Dew Point ◽  
Plait Point ◽  
Bubble Point ◽  
Reservoir Fluid ◽  
Point Curve ◽  
The Rich ◽  
Gas Drive

Stalkup, Fred I., Junior Member AIME, The Atlantic Refining Co., Dallas, Tex. Abstract Vapor-liquid phase equilibrium experiments have been conducted in a static equilibrium cell on mixtures of a light, 450 API stock-tank gravity reservoir fluid and a rich hydrocarbon gas containing approximately 55 mole per cent of intermediate hydrocarbons. Both a pressure-vs-composition study of the gas and a simulated reservoir fluid, and a multiple-batch contact simulation of the condensing-gas-drive oil recovery process were performed. In the latter experiments equilibrium gas and liquid compositions were analyzed. Also, conventional, "condensing-gas-drive", long-tube displacement experiments of the reservoir fluid and gases of various richness were performed. The results of these experiments could not be satisfactorily interpreted by the conventional pseudo-ternary-diagram representation of multicomponent phase behavior. The results seem to be explained better by considering a bubble-point surface and a dew-point surface joined in a plait-point locus. Portions of the plait-point locus cannot be "seen" directly by the rich hydrocarbon gas because of curvature of the dew-point surface. In such a system, continuous injection of the rich gas over stationary reservoir fluid might form a zone of contiguously miscible compositions from pure rich gas to pure reservoir fluid by:saturating the reservoir fluid with injected gas to the bubble-point surface;creating by mass transfer with fresh injected gas a path of contiguously miscible compositions along the bubble-point surface to the plait-point locus; andcreating by mass transfer with additional injected gas a path of gas compositions along the dew-point surface up to the point where direct miscibility results between dew-point fluid and the injected rich gas. Introduction The use of the pseudo-ternary-phase diagram to illustrate miscible displacement phase behavior has been discussed by several authors. Such a representation of phase behavior is not rigorous, but the ternary diagram nevertheless gives a qualitative picture of what actually occurs in a miscible displacement process. Fig. 1 is a typical illustration of miscible displacement phase behavior by a ternary diagram. The multicomponent hydrocarbon system is divided into three pseudo-components: a light fraction containing methane and nitrogen, an intermediate fraction containing ethane through hexanes plus carbon dioxide, and a heavy fraction containing heptane and heavier components. A two-phase region is bounded by a dew-point curve and a bubble-point curve, which are joined at the critical point. The concept deduced from such a representation for miscible displacement by a condensing-gas-drive process is as follows: a rich gas G, which lies to the right of the limiting tie line through the critical point C, is injected into the reservoir and contacts reservoir fluid L, saturating the reservoir fluid to give bubble-point fluid L1 and equilibrium dew-point gas G1. Continued injection of rich gas changes the composition of the saturated liquid L1 through a series of liquid compositions lying along the bubble-point curve, until the critical composition C is reached, at which point direct miscibility with the rich gas is achieved. Some equilibrium gas with compositions lying along the dew-point curve from G1 to C is also formed in this process. SPEJ P. 184ˆ

Miscibility Relationships in the Displacement of Oil By Light Hydrocarbons

1962 ◽  
Vol 2 (04) ◽  
pp. 340-346 ◽  
Author(s):  
W.M. Rutherford
Keyword(s):  
High Pressure ◽  
Critical Temperature ◽  
Phase Behavior ◽  
Experimental Methods ◽  
Miscible Displacement ◽  
Hydrocarbon Mixtures ◽  
West Texas ◽  
Displacement Experiments ◽  
The Subject ◽  
Gas Drive

Abstract A knowledge of the limits of miscibility between reservoir oil and possible injection fluids is required for selection of the optimum miscible-injection fluid. Limits of miscibility can be estimated from the results of equilibrium phase-behavior experiments. They can also be determined by means of displacement experiments conducted in a high-pressure sandpack. This paper describes the equipment and procedure which have been developed for determining miscibility conditions by stable displacement. A systematic series of displacements of a West Texas reservoir oil was carried out. The results indicate that, at constant pressure, miscibility is a function only of the pseudo critical temperature of the injection gas. This fact, together with improved experimental methods, makes the displacement technique a rapid, reliable means for determining miscibility conditions. In conjunction with the displacement experiments, phase diagrams were constructed for the oil with dry gas and propane and with dry gas and ethane. Phase behavior of the methane-ethane-propane system was determined at 110 degrees F. The experimental work demonstrates the feasibility of using ethane-rich gases to reduce cost and pressure requirements for miscible displacement. Introduction In recent years, interest in the miscible displacement of oil by light hydrocarbon mixtures has been high. Many pilot and a few field scale projects have been started. These projects have made use of various methods for achieving miscibility:the LPG-slug process,the enriched-gas-drive process andthe high-pressure gas-drive process. Some field projects have been successful; the results of others are debatable. In general, projects which have performed best have involved the injection of an appreciable fraction of a pore volume of miscible material. Economical application of miscible displacement depends strongly on the cost of the miscible-injection fluid. If an appreciable fraction of a pore volume of material is required for successful application of these methods, a precise knowledge of the minimum requirements for miscibility in terms of composition of injection fluid is essential. Therefore, reliable experimental methods for determining miscibility conditions are important, and a procedure for estimating these conditions from the composition of the reservoir fluid is highly desirable. The subject of this paper is the problem of determining conditions which result in miscible displacement of oil by light hydrocarbon mixtures. Miscibility conditions can be estimated by means of equilibrium experiments conducted in a PVT cell, or they can be determined by means of high-pressure displacement experiments. This paper describes the equipment and procedure which have been developed for the determination of miscibility by high-pressure displacement experiments. These methods have been applied to the displacement of a West Texas reservoir oil with mixtures of dry gas, ethane and propane. In conjunction with the displacement experiments, triangular phase diagrams have been constructed for mixtures of the oil with dry gas and propane and with dry gas and ethane. The effect of injection-gas composition on conditions for miscible displacement in high-pressure sandpacks and cores has been the subject of several published papers. The experimental methods used in these investigations were such that displacements were unstable, and the effects of fingering and/or gravity layover are clearly evident in the results. Miscibility conditions were probably correct in spite of the instability phenomena, but the experiments evidently were time-consuming, and limited data were reported. Systematic high-pressure flow studies which would support a correlation of miscibility conditions have not been reported; however, Wilson has proposed the use of pseudo critical temperature of the injection gas as a parameter and Benham, et al, have based a miscibility correlation on observed and calculated equilibrium data. SPEJ P. 340^

Effects of Hardness and Cosurfactant on Phase Behavior of Alcohol-Free Alkyl Propoxylated Sulfate Systems

SPE Journal ◽  
2015 ◽  
Vol 20 (05) ◽  
pp. 1145-1153 ◽  
Author(s):  
Maura C. Puerto ◽  
George J. Hirasaki ◽  
Clarence A. Miller ◽  
Carmen Reznik ◽  
Sheila Dubey ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Equilibrium Phase ◽  
Optimal Conditions ◽  
Lower Phase ◽  
Blend Ratio ◽  
Internal Olefin ◽  
Internal Olefin Sulfonate

Summary The effect of hardness was investigated on equilibrium phase behavior in the absence of alcohol for blends of three alcohol propoxy sulfates (APSs) with an internal olefin sulfonate (IOS) with a C15–18 chain length. Hard brines investigated were synthetic seawater (SW), 2*SW, and 3*SW, the last two with double and triple the total ionic content of SW with all ions present in the same relative proportions as in SW, respectively. Optimal blends of the APS/IOS systems formed microemulsions with n-octane that had high solubilization suitable for enhanced oil recovery at both ≈25°C and 50°C. However, oil-free aqueous solutions of the optimal blends in 2*SW and 3*SW, as well as in 8 and 12% NaCl solutions with similar ionic strengths, exhibited cloudiness and/or precipitation and were unsuitable for injection. In SW at 25°C, the aqueous solution of the optimal blend of C16–17 7 propylene oxide sulfate, made from a branched alcohol, and IOS15–18, was clear and suitable for injection. A salinity map prepared for blends of these surfactants illustrates how such maps facilitate the selection of injection compositions in which injection and reservoir salinities differ. The same APS was blended with other APSs and alcohol ethoxy sulfates (AESs) in SW at ≈25°C, yielding microemulsions with high n-octane solubilization and clear aqueous solutions at optimal conditions. Three APS/AES blends were found to form suitable microemulsions in SW with a crude oil at its reservoir temperature near 50°C. Optimal conditions were nearly the same for hard brines and NaCl solutions with similar ionic strengths between SW and 3*SW. Although the aqueous solutions for the optimal blends with crude oil were slightly cloudy, small changes in blend ratio led to formation of lower phase microemulsions with clear aqueous solutions. When injection and reservoir brines differ, it may be preferable to inject at such slightly underoptimum conditions to avoid generating upper phase, Winsor II, conditions produced by inevitable mixing of injected and formation brines.

Equilibrium Phase Compositions of CO2/Crude Oil Mixtures-Part 2: Comparison of Continuous Multiple-Contact and Slim-Tube Displacement Tests

1983 ◽  
Vol 23 (02) ◽  
pp. 281-291 ◽  
Author(s):  
Franklin M. Orr ◽  
Matthew K. Silva ◽  
Cheng-Li Lien
Keyword(s):  
Phase Composition ◽  
New Mexico ◽  
Crude Oil ◽  
Phase Behavior ◽  
Equilibrium Phase ◽  
Saturation Pressure ◽  
Research Center ◽  
Displacement Efficiency ◽  
Ternary Diagrams ◽  
Oil Mixtures

Orr Jr., Franklin M.; SPE; New Mexico Petroleum Recovery Research Center Petroleum Recovery Research Center Silva, Matthew K.; SPE; New Mexico Petroleum Recovery Research Center Petroleum Recovery Research Center Lien, Cheng-Li; SPE; New Mexico Petroleum Recovery Research Center Abstract Results of phase composition and density measurements for CO2/ crude-oil mixtures at 32C and four pressures are reported for a system in which liquid/liquid and liquid/liquid/vapor phase separations occur. The experiments demonstrate that a CO2-rich liquid phase can contain as much as 30 wt% hydrocarbons and show that a CO2-rich vapor phase at the same conditions extracts hydrocarbons less efficiently. Pseudoternary phase diagrams are presented that summarize the results of the detailed phase composition measurements. Results of slim-tube displacements at the same four pressures are also given. They indicate that displacement is efficient when the pressure is high enough that a liquid CO2-rich phase appears. Predictions of the performance of the slim-tube displacements based entirely on the performance of the slim-tube displacements based entirely on the experimental measurements of phase compositions and densities are obtained using a simple one-dimensional (1D) simulator. The simulation results clarify the roles of phase behavior and volume change on mixing in the slim-tube tests. Finally, the advantages and limitations of the slimtube and continuous multiple-contact (CMC) tests are compared. We conclude that the CMC experiment yields more information useful for prediction of the performance of a CO2 flood. Introduction The laboratory experiment most commonly performed in the evaluation Of CO2 flood candidates is the slim-tube displacement. The experiment is an attempt to isolate the effects of phase behavior on displacement efficiency in a flow setting that minimizes the effects of the viscous instability inherent in the displacement of oil by low-viscosity CO2. It provides useful information about the pressure required to produce high displacement efficiency in an ideal porous medium. It is not, however, a direct measurement of the phase behavior Of CO2/crude-oil mixtures. The physical behavior of such mixtures is usually studied by combining known quantities of oil and CO2 in a visual cell and measuring phase volumes at various pressures. The volumetric data obtained, along with saturation pressure pressures. The volumetric data obtained, along with saturation pressure data, do not give any direct evidence concerning displacement efficiency, but they can be used to adjust and tune representations of the phase behavior with an equation of state (EOS). For instance, Sigmund et al., used that procedure to match EOS calculations to PVT data and then simulated slimtube displacement experiments, obtaining good agreement between calculation and experiment. Gardner et al., used a combination of phase composition and volumetric measurements to construct ternary diagrams phase composition and volumetric measurements to construct ternary diagrams for a CO2/crude-oil system and then used the ternary diagrams in 1D simulations of slim-tube displacements. They also obtained good agreement between calculation and experiment. Thus there is at least some experimental confirmation of the relationship between equilibrium phase behavior and flow in an ideal porous medium. The connection between phase behavior and displacement efficiency has, of course, long been recognized. SPEJ p. 281

Sign in / Sign up

Export Citation Format

Share Document