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    • 专利摘要:
    A method for recovering hydrocarbons from a formation comprises injecting a displacement fluid in the formation to create a liquid-liquid phase equilibrium (LLE) between the hydrocarbons and the displacement fluid. The method comprises injecting the displacement fluid, e.g. carbon dioxide, under conditions of pressure and/or temperature such that an immiscible carbon dioxide-hydrocarbons system is in liquid liquid equilibrium (LLE) at least at and/or near the displacement front.
    公开号:DK201570232A1
    申请号:DK201570232
    申请日:2015-04-20
    公开日:2015-05-04
    发明作者:Kristian Mogensen；Niels Lindeloff；Søren Frank
    申请人:Mærsk Olie Og Gas As；
    IPC主号:
    专利说明:

    Method of Displacing Hydrocarbons in a Formation
    FIELD OF THE INVENTION
    The present; Invention relates to a method for Enhanced Oil Recovery (EOR) in a formation, and in particular, though not; exclusively, to a method for recovering oil from a formation by injection of a displacement fluid under liquid-liquid equilibrium.
    BACKGROUND TO THE INVENTION
    Carbon dioxide injection (002) for Enhanced Oil Recovery (EOR): purposes have been applied in a number of oil fields across the world, often in combination with water injection in the SQ-cailed 'water-alternating-gas (WAG) process , as reported in numerous publications such as Mungan, N.: "Carbon Dioxide Flooding Fundamentals," J. Cdn. Pet. Tech. (January-March 1981) 87; Langston, MV, Hoadley, SF, and Young, D.N. : "Definitive C02 Flooding Response in the SAOROC Unit", paper SPE / BOE 17321 presented at the 1988 SPE / DOE Enhanced Oil Recovery Symposium, Tuisa, April 17-20; Tanner, CS et al .: "Production Performance of the Wasson Denver Unit C02 Flood, "paper SPE / DOE 24156 presented at the 1992 SPE / DOE Symposium on Enhanced Oil Recovery, Tulsa, April 22-24; Kittridge, MG:" Quantitative 002 Flood Monitoring, Denver Unit, Wasson (San Andres) Field " , paper SPE 24644 presented at the 1992 SPE Annual Technical Conference and Exhibition, Washington, DC, October 4-7; Hsu, G.-F ,, Moreil, J.L., and Fails, A.H .: "Field-Scale C02 Flood Simulations and Their Impact on the Performance of the Wasson Denver Unit," paper SPE 29116 presented at the 1995 SPE Symposium on Reservoir Simulation, San Antonio, Texas, February 12-15; Harpoie, KJ. and Hailenbeck, LD: "East Vacuum Grayburg San Andres Unit C02 Flood Ten Year Performance Review: Evolution of a Reservoir Management Strategy and Results of WAG Optimization ^ paper SPE 36710 presented at the 1996 SPE Annual Technical Conference and Exhibition, Denver, 6-9 October; Ring, JN and Smith, D.3: "An Overview of the North Ward Estes CQZ Flood", paper SPE 30729 presented at the 1995 SPE Annua! Technical Conference and Exhibition, Dallas, October 22-25; Brokmeyer, RJ , Boriing, DC, and Pierson, WT: "Lost Soldier Tensieep C02 Tertiary Project, Performance Case History: Bairoil, Wyoming", paper SPE 35191 presented at the 1996 SPE Permian Basin Oil and Gas Recovery Conference, Midland, Texas, 27-29 March; Flanders, WA and DePauw, RM: "Update Case History: Performance of the Twofreds Tertiary C02 Project", SPE 26614 presented at the 1993 SPE Annual Technical Conference and Exhibition, Houston, October 3-6, Beiiayance, JFR: "Doliarhide Devonian C02 Flood; Project Performance Review 10 Years Later ", paper SPE 35190 presented at the 1996 SPE Permian Basin Oil and Gas Recovery Conference, Midland, Texas, March 27-29 ;; and Pittaway, KR and Resate, RJ: 'The Ford Geraldine Unit C02 Flood -Update 1990 ", SPERE (1991) 410. A reason for the interest in CO2 as an EOR injector relates- to its soluhiiiiy in hydrocarbons. Typically, C02 becomes: miscible With; crude oil at much lower pressures than other gases employed in EOR techniques such as methane or nitrogen. It is generally accepted that a miscible displacement yields better hydrocarbon recovery than an immiscible drive, where a portion of the gas forms due to buoyancy, an override zone leading to early gas breakthrough, as illustrated in Figures 1A and 1B.
    The phase behavior of C02 - hydrocarbon systems can be quite complex, especially at lower temperatures, i.e. below 120 ° F (4§ ° C) where more than two phases may be in equilibrium. Such temperatures may occur naturally (e.g. in shallow reservoirs), or as a result of introduction of injection water at temperatures below the original reservoir temperature. An example of a system with more than two phases in equilibrium is a Vapor-Liquid-Liquid Equilibrium (VLLE) systems. Observation of Vapor-Liquid-Liquid Equilibrium (VLLE) phase behavior In GOa ^ hydrocarhon systems have been reported in literature, for example in Huang, E.T.S. et at: "The displacement of residual oil by carbon dioxide", paper SPE 473¾ presented at the 8PE ΑΙΜΕ Improved Gil Recovery Symposium, Tulsa, Oklahoma, April 22-24, 1974; Shelton, J.L., Yarborough, L .: "Multiple phase behavior in porous media during CQ2 or rich-gas flooding", paper SPE 5827, SPE Journal, 1171-1178, 1977; Metcalfe eta I.: "The effect of phase equilibria on the C02 displacement mechanism", paper SPE 7061, SPE Journal, 242-252¾ 1979; Yeiiig, WF: "Carbon dioxide displacement of a West Texas reservoir oil", paper SPE 9785, presented at the 1981 SPE EOR Symposium, Tulsa April 5-8 1981; Orf, FM et al: "Phase behavior of C02 and Crude oil in Idw-temperature reservoirs", paper SPE 8813, SPE Journal, 480-492, 1981; Turek , EA, et al .: "Phase equilibria in carbon dioxide - multicomponent hydrocarbon systems: Experimental data and an improved prediction technique", paper SPE 9231, SPE Journal, 308-324, June 1984; Larson et al .: "Temperature dependence of L1 / L2 / V behavior in C02 / Hydrocarbon systems ", paper SPE 15399, SPE Reservoir Engineering, 105-114, February, 1989; and Staikup, FJ," Miscellaneous Displacement ", SPE Monograph Series, SPE, Richardson, Tx, 1992. A further complexity may arise when the addition of C02 leads to precipitation of asphaltenes from the oil, which is either reported as a VLLE, or more commonly as a Vapor-Liquid-Solid Equilibrium (VLSE) system. Several publications address this topic, such as Novosad, 2 ,, Costain, TG: "Experimental and modeling studies of asphaltene equilibria for a reservoir under C02 injection", paper SPE 20530 presented at the SPE Annua] Technical Gonference and Exhibition, New Orleans, Louisiana, September 23-26, 1990; Monger, TO., Trujillo, DE: 'Organic deposition during G02 and rich-gas flooding'. Paper SPE 18063, SPE Reservoir Engineering, 6, 17-24, 1991; Srivastava, RK ,, Huang, SS, Dong, M. : "Asphaltene deposition during C02 flooding", paper SPE-59092, SPE Producion & Operations, 14, 235-245, 1999; Pafra-Ramirez, M., Peterson, B., Deo, MD: '' Comparison of first arid multiple contact carbon dioxide induced asphaltene precipitation ", paper 8PE 65019 presented at the 8PE International Symposium on Oilfield Chemistry, Houston, Texas, February 13-16, 2001; and Broad, J. et al: "Deposition of 'asphaltenes' during COg injection and (implications for EEA description and reservoir performance", paper I PTC 11563 presented at the International Petroleum Technology Conference, Dubai, UAE, December 4-6, 2007 .
    For a given temperature, the lowest pressure at which an injection gas becomes miscible with hydrocarbons is referred to as the minimum miscibility pressure (MMP):, The MMP for C02 is considered an important parameter for the economics of a C02 flood. However, estimating the MMP is not trivial. Early attempts at predicting C02 MMP relied on empirical correlations whereas modern algorithms are anchored within an Equation of 8; tate (EOS) model framework.
    Ternary diagrams and pseudo-ternary diagrams with the reservoir fluid lumped into three components are useful in explaining the concept of miscibility but are not applicable to multi-component mixtures. Not only are the ternary diagrams limited to three-component mixtures, they are also limited to vaporizing and condensing drives and do not consider the combined vaporizing / condensing mechanism which determines the MMP tor most gas-crude oil mixtures, as reported for example in Ziok , AAj "A combined condensation / vaporizing mechanism in the displacement of oil by enriched gases", paper SPE 1S4983, presented at SPE ATCE. New Orleans, LA, October 5-8, 1986, With C02 as injection gas the combined vaporizing / condensing mechanism is dominant. Some C02 will condense into the oil phase, while intermediate molecular weight hydrocarbons from the oii phase will vaporize and mix with the GO -Rich gas phase, as illustrated in Figure 2. A number of methods exist for predicting the MMP in an injection gas. / hydrocarbon system. For multi-component mixtures, simulations of the MMP typically rely on cell-to-ceil slimtube simulations (Metcalfe, RS, Fussell, DD and Fusseil, JL: "A muiticeli equilibrium separation model for the study of multiple contact miscibility in rich gas drives ", presented at the SPE-AIME 47th Annual Meeting, San Antonio, TX, October 8-1¾1172) or 1-D reservoir simulations or tie-line multicomponent MMP simulation algorithms taking into consideration the vaporizing / condensing mechanism (Orr, FlM. , "Theory of Gas Injection Processes", Tie-Line Publications, Holte, Denmark, 2007; Jessen, K., Mieheisen, ML and Stenby, E.: "Global approach for calculating minimum miscibility pressure", Fluid Phase Equilibria 153, 251-263, 1998). The swelling experiment (where successive amounts of gas are added to the crude oil) yields a key data set for EOR Equation of State (EOS) model development. The experiment produces extensive volumetric data to which the EOS model can be tuned. A swelling test further targets the critical inversion occurring when consecutive injections of gas propel the system from bubble point to dew point behavior, A match Qf the critical point on the swelling curve is a prerequisite for correlating the MMP of the system. Although the critical composition at MMP will be generally identical to the critical composition observed in a swelling experiment, a good match of the critical point on the swelling curve provides evidence that the developed EOS model captures the vaporizing and condensing mechanisms that drive the system towards miscibility.
    However, for some crude oils, particularly for heavy oils, a swelled fluid composition will not become ofifjcai for any amount of injection gas added. This has led a number of investigators to conclude that displacement of heavy oil with C02 will generally yield poor recovery rates, eg due to gravity override and viscous fingering. For such systems the saturation point will, for high gas concentrations, increase steeply with increasing gas mole fraction; the saturation point does not mark the boundary line between an equilibrium gas and liquid, but between two liquid phase compositions in equijibnum. MMP algorithms are attractive because they are fast, but they are applicable for systems involving more than two phases. Also, they will fail to provide an MMP before systems with: two immiscible liquid phases. Although this is the correct response * it leaves the investigator with no information about the displacement,
    To gain further knowledge about such systems it is known to carry out a smart sim © procedure. A smart simulation will develop zones of constant gas and liquid composition (Zhao, GB, Ad id harm a, H., Towler, B ,, Radosz, Μ .: '' Using a muitiple-mixing-celi model to study minimum miscibility pressure controlled by thermodynamic equilibrium tie lines ", Ind. Eng, Ghem. Res. 45, 7913-7923, 2006) and will further quantify the recovery at pressures without miscibility. U.S. Patent No. 3: 084,743 (West et at.) discloses a A fluid comprising gaseous or liquefied carbon dioxide is injected into an oil reservoir under sufficiently high pressure to form two immiscible phases, one mostly hydrocarbons with carbon dioxide dissolved therein, and the other mostly carbon dioxide. with hydrocarbons: dissolved therein, in a two-phase vapor-Hquid equilibrium (VLEj system, US Patent No, 5,046,561 (Huang et a !,) discloses a method for achieving multiphase generation conditions for recovery of hydrocarbon products from a high temperature reservoir. The method of US 5,046,561 operates within a vapor-liquid-equilibrium (VLLE) three-phase region. US Patent No. 3,623,552 (Vairogs et al.) Discloses the recovery of oil by injecting an oil miscible gas such as carbon dioxide into a subterranean oii reservoir. The carbon dioxide is introduced under conditions of pressure and temperature so that a three-phase VLLE equilibrium is disclosed, U.S. Patent No. 4,557,330 (Fusseis et al.) Discloses a method for displacing hydrocarbons from a subterranean reservoir by injecting a displacing fluid such as carbon dioxide and an additive. The method discloses expanding the VLLE region by using additives to the C02 phase. US Patent No. 4,617,996 (Shu) discloses recovery of oil from subterranean reservoirs using carbon dioxide as a displacement fluid under immiscible displacement conditions by adding a € 2 + additive to increase the solubility of the carbon dioxide in the Oil. This method involves using additives to lower oil viscosity and hence improve sweep efficiency of an immiscible VLB drive.
    It is among the objects of the present invention to obviate and / or mitigate at least one of the aforementioned disadvantages.
    SUMMARY OF THE INVENTION
    According to a first aspect of the present invention, there is provided a method for recovering hydrocarbons from a formation comprising injecting a displacement fluid into the formation to create a liquid-liquid phase equilibrium (; LLE) between the hydrocarbons and the displacement fluid.
    The method may be enterprise creating; and / or maintaining a liquid-liquid phase equilibrium in the formation in situ. The method may involve creating and / or maintaining a liquid-liquid phase equilibrium in the formation: at least at or near a displacement: front. The displacement front will be understood herein; to refer to a region of the formation where the hydrocarbons are displaced by the displacement fluid and / or to a region of interface between the hydrocarbons and the displacement fluid.
    The formation may typically comprise a subterranean formation.
    In one embodiment, the displacement fluid may comprise carbon dioxide. The method may comprise creating and / or maintaining a liquid-liquid equilibrium between the hydrocarbons and the carbon dioxide. In other embodiments, the displacement fluid may comprise nitrogen, methane, or the like.
    The method may comprise maintaining at least one region of the formation under conditions ·, · e.g. temperature and / or pressure * prodding a liquid-liquid equilibrium between the hydrocarbons and the displacement fluid.
    The method may comprise controlling temperature and / or pressure in at least one region of the formation to provide and / or maintain a liquid-liquid phase between the hydrocarbons and the displacement fluid,
    The method may comprise injecting the displacement fluid, eg, carbon dioxide, under conditions of pressure and / or temperature such that an immiscible carbon dioxide hydrocarbon system, for example at least at and / or near the displacement front, is in liquid-liquid equilibrium (LIE).
    Operating under LIE conditions may provide two Immiscible liquid phases of similar densities in equilibrium, rather than a vapor-liquid equilibrium (VLE) system. Provision of a displacement front having two liquid phases of similar densities may advantageously significantly increase the rate of oil recovery when compared to a vapor-liquid front in which the vapor and liquid phases have very different densltiM.
    The method may create a first phase, e.g. a first liquid phase, at least on the displacement front. The first phase may comprise a first or high concentration of carbon dioxide and a first or low concentration of hydrocarbons.
    The method may comprise creating a second phase, e.g. a second liquid phase, at least on the displacement front. The second phase may comprise a second or low concentration of carbon dioxide and a second or high concentration of hydrocarbons.
    The terms high and low will herein be understood as being relative terms between the first and second phases, e, g. first and second liquid phases. The first or high concentration of carbon dioxide in the first phase may be higher than the second or low concentration of carbon dioxide in the second phase. The first or low concentration of hydrocarbons in the first phase may be lower than the second or high concentration of hydrocarbons in the second: phase.
    The first phase and second phase may be created and / or may exist in equilibrium by virtue of the conditions, e.g. temperature and / or pressure, in the formation, for example by the pressure of displacement fluid injected into the formation.
    The method may operate under a predetermined pressure and / or a predetermined range of pressure. The pressure may be less than or equal to, typically less than, the maximum overburden strength. The maximum overburden strength will be understood as the maximum pressure over which the rock overburden the formation reservoir containing the hydrOcSfbohs is capable of withstanding without suffering significant damage. The maximum: overburden strength may typically be determined and / or dictated by the characteristics of the overburden in a particular rock formation.
    The method may comprise measuring and / or determining the maximum overburden strength. The method may comprise performing a so-called formation integrity test, e, g, during drilling; a so-caiied step-rate test, e, g. during normal water injection operation; and / or a core analysis, such as in a core analysis lab, e.g. a confined pressure cell. The method may comprise selecting an operating pressure below or up to the maximum overburden strength.
    The method may operate under temperature and / or a range of temperature which yields LLE phase behavior for the selected pressure and / or range of pressure. It will be understood that an LLE phase behavior may exist only below a certain temperature; (Tmax) above which the displacement fluid-hydrocarbon system may become a VLE system with a critical point Accordingly, the method may operate under temperature below Tmax such that the hydrocarbons and the displacement fluid may exist in a liquid-liquid equilibrium.
    The method may comprise cooling at least one region of the formation. This: may be advantageous, for example if the temperature in the formation is above the Tmax. Cooling the formation may allow carrying out the method at a temperature below Tmax, which may permit creation of a liquid-liquid equilibrium, e.g. at Or near the displacement front. The method may comprise injecting a cooling fluid, e.g. water, in the formation. In such an instance, the method may comprise a so-called water-alternating-gas (WAS) injection step.
    The method may comprise controlling the temperature of the dispensing fluid, e.g. carbon dioxide, for example, by cooling the displacement fluid below the maximum temperature (Tmax), such as before injection. By such provision the temperature in the formation, e.g. at or near the displacement front, may be controlled, regulated, and / or may be maintained at a temperature below Tmax,
    Typically, the maximum temperature (Tmax) may be less than or equal to approximately 120T (49X). The maximum temperature (Tmax) may be in the region of 1 Q0 ° F (38 X) to 120T (49X), e.g. may be approximately 120T (49X). However, it is appreciated that the maximum temperature Tmax may depend on the characteristics of a particular formation and / or hydrocarbons therein.
    The method may comprise carrying out preliminary experiments and / or tests in the formation. The method may comprise performing one or more experiments and / or tests selected from the list of differentia! vaporization (DV), constant-composition expansion (CCE), swelling tests, sllmtube tests, and three-phase equilibrium VLLE tests, iy such provision it may be possible to obtain data and / or information about the formation and fluids therein in order to select appropriate parameters, eg temperature and / or pressure, in the present method.
    The method may comprise using a thermodynamic model, such as an equation of state (EOS). The method may comprise using data and / or information obtained from one or more experiments and / or tests, to input and / or tune the thermodynamic model.
    With such provision, it may be possible to determine from the thermodynamic model, such as an equation of state (EOS), the conditions suitable for creating a liquid-liquid equilibrium (LLE) displacement front.
    The thermodynamic model may comprise a major equation: of state, e.g. a Redlich-Kwong (RK) EOS, or a Soave-Redlich-Kvvong (SRK) EOS, or a Peng-Robinson (PR) EOS. In one embodiment, the thermodynamic model may comprise a Soave-Redlich-Kwong EOS *
    The method may comprise determining the maximum temperature (Tmax) tip to which an LIE phase behavior exists. The method may comprise using a thermodynamic model, e.g. an equation of state (EOS) such as an SRK EOS, to predict behavior, e.g. swelling behavior, at different temperatures. The method may comprise inputting the data and / or information obtained during one or mote experiments and / or tests in the thermodynamic model, e.g. equation of state (EOS). The method may comprise running the thermodynamic model, e.g. equation of state (EOS), with said data and / or information obtained during one of more experiments and / or tests, so as to determine behavior, e.g. to different temperature. This may allow a user to determine the temperature Tmax: below which the displacement fluid-hydrocarbon system may exhibit LLE phase behavior, and above which the displacement fluid-hydrocarbon system may exhibit VLB phase behavior with a critical point. It will be appreciated that miscibility may develop between the displacement fluid and the hydrocarbons below the available range of temperature © for the formation, and the available range of injection pressure, in such an instance I will be appreciated that it may not be possible, or advantageous , to achieve a liquid-liquid equilibrium (LLE) displacement front.
    The method may comprise constructing one or more phase diagrams for a system comprising the displacement fluid and the hydrocarbons. Typically, the phase diagram may comprise regions of vapor (V). liquid (L), vapor-liquid equilibrium (V + L), iiquid-liquid equilibrium (L + L), and / or vapor-liquid-equilibrium (V + L + L), e.g. for one or more combinations of pressure, temperature and mole fraction of displacement fluid injected.
    The method may comprise cooling at least one region of the formation, for example if the temperature in the formation is above the maximum temperature Tmax. Cooling the formation may allow carrying out the method at a temperature below Tmax, which may permit creation of a liquid-liquid phase equilibrium displacement front. The method may comprise injecting a cooling fluid, e.g. water, in the formation, in such an instance, the method may comprise a so-Calied water-alternating-gas (WAG) injection step.
    The method may comprise injecting the displacement fluid, e.g. carbon dioxide, at a temperature lower than or equal to the maximum temperature Tmax. This may allow the method to create and / or maintain LLE phase behavior at least in a region of the formation such as at or near the displacement front, which may advantageously lead to higher displacement and / or recovery of hydrocarbons.
    The method may comprise injecting the displacement fluid, e.g., carbon dioxide, from one or more wellbores, e.g. injection wellbore.
    The method may compose recovering: hydrocarbons from: one or more wellbores, e.g. production wellbore.
    The method may include closing one or more wellbores, above: and / or below the formation. This may assist in injecting the displacement fluid preferentially into the formation, and / or in recovering hydrocarbons to surface. The method may typically comprise closing one or more injection wellbores and / or one or more production wellbores using one or more plugs such as so-called 'bridge plugs'.
    The method may comprise measuring and / or monitoring pressure and / or temperature * e.g. in and / or near the formation, e.g. in one or more injection wellbores and / or in one or more production wellbores.
    According to a second aspect of the present invention there is provided a subterranean system comprising: a formation, the formation comprising hydrocarbons; and a displacement fluid for displacing hydrocarbons from the formation, while the hydrocarbons and the displacement fluid are in a liquid-liquid phase equilibrium: fl-LE).
    The hydrocarbons and the displacement fluid may exist in liquid-liquid phase equilibrium (ELI) in the formation, e.g. in situ. The hydrocarbons and the displacement fluid may exist in liquid phase equilibrium in the formation at least at or near a displacement front.
    The formation may typically comprise a Subterranean formation.
    In one embodiment, the displacement fluid may comprise carbon dioxide; in other embodiments, the displacement: fluid may comprise nitrogen, methane or the like.
    The features described in relation to any other aspect or the invention may apply in respect of the system according to a second aspect of the present invention and are therefore not repeated here for brevity.
    According to a third aspect of the present invention there is provided a subterranean system for recovering hydrocarbons from a formation, wherein the subterranean system is adapted to inject a displacement fluid into the formation, and the subterranean system is configured to create an iiquid-iiquid phase equilibrium (LLE) between the hydrocarbons and the displacement fluid.
    The subterranean system may comprise injection means, such as one or more injection wells, for injecting the displacement fluid into the formation.
    The system may be configured to create and / or maintain a liquid-liquid phase equilibrium in situ formation, .e.g, at least at or near a displacement front.
    The formation may typically comprise a subterranean formation.
    In one embodiment, the displacement fluid may comprise carbon dioxide; in other embodiments, the displacement fluid may comprise nitrogen, methane, or the like.
    The system may be configured to maintain at least one region of the formation under conditions, e.g. temperature and / or pressure, providing an equilibrium equilibrium between the hydrocarbons and the displacement fluid.
    The system may comprise at least one temperature monitoring unit to measure and / or monitor temperature in at least a portion of the formation. The at least one temperature monitoring unit may be provided in the formation, in one or more injection wells, or any other suitable location.
    The system may comprise at least one temperature regulating unit to control and / or regulate temperature in at least a portion of the formation, e.g. at or near a displacement front.
    At least one temperature regulating unit may be configured to control and / or regulate the temperature of the displacement fluid, e.g. carbon dioxide.
    At least one temperature regulating unit may be configured to control and / or regulate a temperature regulating fluid, e.g. water. Conveniently, the temperature regulating fluid, e.g. water, may be injected separately from the displacement fluid.
    The system may comprise at least one pressure monitoring unit to measure and / or monitor pressure in at least a portion of the formation. The at least one pressure monitoring unit may be provided in the formation, in one or more injection wells, or any other suitable location.
    The system may comprise at least one pressure regulating unit to control and / or regulate pressure in at least a portion of the formation, e, g. at or near a displacement front.
    At least one pressure regulating unit may be configured to control and / or regulate pressure of the displacement fluid, e.g. carbon dioxide.
    The features described in relation to any other aspect or the invention may apply in respect of the system according to a third aspect of the present Invention, and are therefore not repeated here for brevity,
    LETTER PiEStSRlPTION OF THE DRAWINGS
    These other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
    Figure 1A is a schematic cross-sectional view of a formation comprising an immiselbie displacement fluid / hydrocarbon system in vapor-liquid equilibrium ^
    Figure 1B is a schematic cross-sectional view of a formation composing a miscible displacement fluid / hydrocarbon system;
    Figures 2Å and 2B are schematic views of a typical vaponzing / condensing mechanism for a displacement fluid / hydrocarbon system;
    Figures 3A and 3B show the results of thermodynamic modeling carried out on hydrocarbons obtained from an oil field operated by Maersk Oii;
    Figure 4 shows a phase diagram for the system of Figure 3 at T = 10Q ° F (38 ° C) f
    Figure 5A is a schematic phase diagram of the system of Figure 3 at T = 10O ° F
    Figure 5B is a schematic phase diagram of the sphere of Figure 3 at T = 133 ° F (56 * 0); spirit
    Figure 6 is a graph showing oil recovery in a siimtube experiment using hydrocarbons obtained from an oil field operated by Maersk Oil.
    DETAILED DESCRIPTION OF THE DRAWINGS
    Figures 1A aid 1B illustrate the role of miscibility on hydrocarbon recovery from a formation by injection of a displacement fluid. A displacement fluid, in this embodiment carbon dioxide, is injected from an injection wellbore 12 into a formation 14, A production wellbore 16 is located on a side of the formation 14 opposite the injection wellbore 12.
    As can be seen in Figure 1 A, when the formation conditions, including temperature and pressure, are such that the displacement fluid and the hydrocarbons form two immiscible phases 22, 24, the lighter GOa-rich phase 22 tends to migrate over or on top of the heavier hydrocarbon-rich phase 24, leading to early gas breakthrough in the production wellbore 16 and therefore reducing the recovery rate of this EQR technique.
    However, as can be seen in Figure 1B, when the formation conditions, including temperature and pressure, are such that the displacement fluid and the hydrocarbons form a measurement system 26, the mixture at the displacement front 28 sweeps the formation 14 substantially from the injection wellbore 12 to the production weiibore 16, thus improving the recovery rate of this EE technique.
    Figures 2A and 2B are schematic views of a typical vaporizing / condensing mechanism for a dispensing fluid 32 / hydrocarbons 34 system, at or near the dispensing front, under immiscible conditions. As illustrated in Figure 2A, a portion of the displacement fluid; phase 3¾ such as carbon dioxide will condense into the hydrocarbons phase 34. Simultaneously, as illustrated in Figure 2B, a portion of the hydrocarbons phase 34, such as low and intermediate molecular weight hydrocarbons, will vaporize and mix Into the .displacement: fluid phase gas 32. Why this may allow recovery of some hydrocarbons from the formation, the recovery rate of an immiscible system: is typically low.
    In an embodiment of the method for recovering hydrocarbons from a formation according to the present invention, the method comprises injecting a displacement fluid such as carbon dioxide into the formation to create and / or maintain a liquid-liquid phase equilibrium (ULE) between the hydrocarbons and the displacement fluid, eg at or near the displacement front and / or a region of interface between the hydrocarbons and the displacement; fluid. Operating under LIE conditions advantageously provides two immiscible liquid phases: of Similar densities in equilibrium, which significantly increases the rate of hydrocarbon recovery when compared to an immiscible system comprising vapor and liquid phases having very different densities.
    In an embodiment of the present invention, in order to determine the conditions, e.g. temperature and / or pressure suitable for providing a liquid-liquid equilibrium between the hydrocarbons and the displacement fluid, the method comprising performing preliminary experiments and / or tests in the formation, e.g., one or more experiments and / or tests selected from the list consisting of differentia! vaporization (DV), constant-composition expansion (CCE), swelling tests, silmtube tests, and three-phase equilibrium VLLE tests. From such tests a user will obtain data and / or information about the formation, which allows the user to use a thermodynamic model, such as an equation of state (EOS), to reproduce the data and / or information obtained during the experiments and / or tests. By such provision, the user can determine from the fhermodynamics model, e.g. EOS, the conditions, e.g. temperature and / or pressure, suitable for operating under a liquid-liquid equilibrium (LLE).
    The data obtained during such experiments allowed a user to determine the maximum temperature Tmax up to which an LLE phase behavior exists,
    Figures 3A and 3B show the results of thermodynamic; modeling carried out on hydrocarbons obtained from an oil fluid Operated by Maersk Oil. In this embodiment, the selected thermodynamic model was the Soave-Redlieh-Kwong (SRK) equation of state (EOS), The SRK EOS was fine tuned using the data and / or information obtained during experiments such as differential vaporization (DV), constant composition composition (CCE); swelling tests, siimfube tests, and three-phase equilibrium VILE tests. In other embodiments, it will be appreciated that other suitable thermodynamic models may be used, such as the Feng-Robinson (PR) EOS.
    The SRK EOS model was tested for injection of successive amounts of gas (in this experiment C02) to the hydrocarbons sample, at different temperatures, in this experiment at T1 = 132 ° F p6 * C), T2 = 125 ° F (52 ° C), T3 = 120 ° F (49 ° C), T4 = 114 ° F (46: 0C), T5 ° 112 ° F (4IX), and T6 = 1Q0 ° F (38 ° C). At temperatures T1, T2, T3 and T4, critical points (01, 02, C3 and 04 respectively); were observed when; consecutive injections of gas drove the system from bubble point to dew point behavior. At T5 = 112 ° F (44 ° C), the system no longer passes through a critical point when CO was added. The Tmax for this hydrocarbon / carbon dioxide system was therefore found to be approximately 112 ° F (44 ° C).
    The obtained data and / or information obtained from the various tests and experiments also allow the user to construct or more phase diagrams for a system comprising the displacement fluid and the hydrocarbons. Figure 4 shows a phase diagram constructed for the carbon dioxide / hydrocarbon system of Figure 3 at T = 100 ° F (38Χ), which is below Tmax. The portion of the phase diagram shown in Figure 4 comprises a region of liquid (L) 42, vapor-liquid equilibrium (V + L) 44, liquid-liquid equilibrium (L + L) 46, and / or vapou ^ liquid liquid equilibrium ( V + L + L) 48. Therefore, it can be seen that, at T = 100 "F (38O0), liquid-liquid equilibrium 48 can be achieved for concentrations of carbon dioxide above approximately 70%, and pressures above approximately 140Q psi (96 bars).
    The maximum operating pressure will be dictated by the overburden strength, which the skilled person can assess by routine analysis of the formation and overburden. The overburden strength can be estimated in a number of ways. A so-called formation integrity test may be carried out, e.g. during drilling, which consists of increasing the mud weight and monitoring the mud balance. Loss of mud to the formation indicates that the breakdown pressure has been exceeded. A so-called step-rate test may be performed during normal water injection operation, where the bottom ^ hole pressure is monitored for increasing injection rates. A change of slope indicates formation breakdown, A third test may consist of being carried out in a core analysis lab in a confined pressure cell
    Figures SÅ and SB illustrate the importance of selecting and controlling the temperature in the formation.
    Figure 5A is a schematic phase diagram of the system of Figure 3 at T ~ 100C, F (38 ° C), which shows the existence of a liquid-liquid equilibrium (L + L) 46 at this temperature. However, as shown in Figure SB, at T = 133 ° F (56 ° C), the LLE region disappears due to the existence of a critical point for the carbon: dioxide / hydrocarbon system. As illustrated in these schematic representations, it can be seen that an LLE phase behavior exists below the maximum temperature Tmax, and that no LLE phase behavior exists above the maximum temperature Tmax.
    Figure 8 is a graph showing oil recovery in a slimtube experiment using hydrocarbons: obtained from an oil field operated by Maersk Oil at a temperature T = 100 ° F (38 ° C). The slimtube experiment was carried out using a highly permeable sand pack which is generally representative of a 1-D dispersion-free displacement. As can be seen in Figure 6, although miscibility does not develop under the selected conditions of pressure and temperature, the recovery rate of hydroGarbpns is nevertheless very high, because the two liquid phases under liquid-liquid equilibrium have similar densities, Έχρ 3Θ ft tube "refers to an iD experiment with a 30-ft long slimming tube (sandpack). SOρ SO ft tube" refers to a 1-D experiment with a 60-ft long slimming tube (sandpack), "Sim" refers to ά slimtube calculation made using and tuned EOS.
    As can be seen, because the two slim tubes are properly packed, dispersion is low, and hence the results from the two slim tubes are similar.
    Various modifications may be made to the embodiment described without departing from the scope of the invention.
    权利要求:
    Claims (33)
    [1]
    A method of recovering hydrocarbons from a formation comprising injecting a displacement fluid into the formation to form a liquid-liquid phase equilibrium (LLE) between the hydrocarbons and the displacement fluid.
    [2]
    The method of claim 1, comprising forming and / or creating a liquid-liquid phase equilibrium in the formation at least at or near a displacement front.
    [3]
    A method according to any preceding claim, comprising controlling temperature and / or pressure in at least one region of the formation to provide and / or maintain a liquid-liquid phase between the hydrocarbons and the displacement fluid.
    [4]
    A method according to any preceding claim, comprising injecting the displacement fluid under such conditions of pressure and / or temperature that an immiscible displacement fluid-hydrocarbon system is in liquid-liquid equilibrium (LLE) at least at and / or near the displacement front.
    [5]
    A method according to any preceding claim, wherein the formation comprises an underground formation.
    [6]
    A process according to any preceding claim, wherein the displacement fluid comprises carbon dioxide.
    [7]
    A method according to any preceding claim, comprising forming a first liquid phase at least at or near the displacement front.
    [8]
    The method of claim 7, wherein the first phase comprises a first or high concentration of displacement fluid and a first or low concentration of hydrocarbons.
    [9]
    A method according to any preceding claim, comprising forming a second liquid phase at least at or near the displacement front.
    [10]
    The method of claim 9, wherein the second phase comprises a second or low concentration of displacement fluid and a second or high concentration of hydrocarbons.
    [11]
    A method according to any one of claims 7 to 10, wherein the first or high concentration of displacement fluid in the first phase is higher than the second or low concentration of displacement fluid in the second phase.
    [12]
    A method according to any one of claims 7 to 11, wherein the first or low concentration of hydrocarbons in the first phase is lower than the second or higher concentration of hydrocarbons in the second phase.
    [13]
    A method according to any preceding claim, comprising operating under a pressure and / or pressure range of less than or equal to the maximum overload strength.
    [14]
    A method according to any preceding claim, comprising operating under temperature and / or a temperature range which provides LLE phase behavior at a selected pressure and / or pressure range.
    [15]
    A method according to any preceding claim, comprising performing one or more experiments and / or experiments selected from the list of differential vaporization (DV), constant-composition expansion (CCE), swelling, slime tube testing and three-phase -equilibrium-VLLE experiments.
    [16]
    A method according to any preceding claim, comprising the use of a thermodynamic model.
    [17]
    The method of claim 16, wherein the thermodynamic model is selected from the list consisting of a Redlich-Kwong (RS) state equation, a Soave-Redlich-Kwong (SRK) state equation and a Peng-Robinson (PR) state equation.
    [18]
    A method according to any of claims 16 to 17, comprising using data and / or information obtained from one or more experiments and / or experiments for input and / or tuning the thermodynamic model.
    [19]
    A method according to any one of claims 16 to 18, comprising using the thermodynamic model for determining the maximum temperature (Tmax) up to which the displacement fluid hydrocarbon system exhibits LLE phase behavior.
    [20]
    A method according to any preceding claim, comprising constructing one or more phase diagrams of a system comprising the displacement fluid and hydrocarbons.
    [21]
    A method according to any preceding claim, comprising cooling at least one region of the formation.
    [22]
    A method according to any preceding claim, comprising injecting the displacement fluid from one or more injection well bores.
    [23]
    A method according to any preceding claim, comprising recovering hydrocarbons from one or more production well bores.
    [24]
    A method according to any preceding claim, comprising measuring and / or monitoring pressure and / or temperature in and / or near the formation.
    [25]
    A subterranean system comprising: a formation comprising hydrocarbons; and a displacement fluid for displacing hydrocarbons from the formation, wherein the hydrocarbons and displacement fluid are in liquid-liquid equilibrium (LLE).
    [26]
    An underground system according to claim 25, wherein the hydrocarbons and displacement fluid are in liquid-liquid phase equilibrium in the formation at least at or near a displacement front.
    [27]
    An underground system according to claim 25 or 26, wherein the displacement fluid comprises carbon dioxide.
    [28]
    An underground hydrocarbon extraction system from a formation in which the underground system is adapted to inject a displacement fluid into the formation and wherein the underground system is configured to form a liquid-liquid phase equilibrium (LLE) between the hydrocarbons and the displacement fluid.
    [29]
    The underground system of claim 28, wherein the underground system comprises injection means for injecting the displacement fluid into the formation.
    [30]
    An underground system according to claim 28 or 29, wherein the system is configured to form and / or maintain a liquid-liquid phase equilibrium in the formation at least at or near a displacement front.
    [31]
    An underground system according to any one of claims 28 to 30, wherein the system comprises at least one temperature monitoring unit for measuring and / or monitoring temperature in at least part of the formation.
    [32]
    An underground system according to any one of claims 28 to 31, wherein the system comprises at least one pressure monitoring unit for measuring and / or monitoring imprints in at least part of the formation.
    [33]
    An underground system according to any one of claims 28 to 32, wherein the displacement fluid comprises carbon dioxide.
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    同族专利:
    公开号 | 公开日
    WO2015028573A1|2015-03-05|
    GB201315349D0|2013-10-09|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    BR112012030921A2|2010-06-04|2016-11-08|Dow Global Technologies Llc|process for oil recovery|
    法律状态:
    2016-06-06| PHB| Application deemed withdrawn due to non-payment or other reasons|Effective date: 20160517 |
    优先权:
    申请号 | 申请日 | 专利标题
    GB201315349A|GB201315349D0|2013-08-29|2013-08-29|Method for displacing hydrocarbons in a formation|
    GB201315349|2013-08-29|
    EP2014068311|2014-08-28|
    PCT/EP2014/068311|WO2015028573A1|2013-08-29|2014-08-28|Method for displacing hydrocarbons in a formation|
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