Determination method of capillary pressure curve and dynamic characterization model in oil displacement process by infiltration control

Abstract

The present invention provides a method for determining a capillary pressure curve and a dynamic characterization model during infiltration-controlled oil recovery. The method for determining the capillary pressure curve includes: constructing a capillary bundle geometric model; respectively determining the initial contact angle, final contact angle and oil-water interfacial tension of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation; constructing a contact angle constitutive model that reflects the change in rock wettability during the infiltration-controlled oil recovery, so as to constrain the size of each capillary contact angle in the capillary bundle geometric model during the displacement-sucking flow simulation; based on the initial contact angle, final contact angle and oil-water interfacial tension of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation and the contact angle constitutive model, using the capillary bundle geometric model, step-by-step controlling the displacement pressure difference to perform multiple rounds of displacement-sucking flow simulation, and obtaining the capillary pressure curves at different stages of infiltration-controlled oil recovery.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a method for determining a capillary pressure curve in an infiltration-controlled oil displacement process and a method for determining a dynamic capillary pressure characterization model thereof. Background Art

[0002] Tight oil, shale oil, and marine carbonate rock have the characteristics of low permeability, complex pore throat structure, strong heterogeneity, and rock tends to be oil-wet or mixed-wet. They face difficulties in production, rapid production decline, low recovery rate, and high mining costs, which need to be solved urgently. Since the pore throat scale of the reservoir is at the micro-nano level, it is difficult to establish an effective displacement system. The development of these types of reservoirs is still in a bottleneck period. Traditional enhanced recovery technologies (polymer flooding, ternary composite flooding, etc.) face technical difficulties such as poor reservoir adaptability and compatibility in promotion and application. Studies have shown that injecting nanofluids, surfactants, salts and other chemical agents into this type of reservoir for infiltration and regulation can gradually change the rock surface from oil-wet or mixed-wet to water-wet, which can greatly reduce the residual oil saturation and improve the efficiency of water flooding. During the infiltration and regulation flooding process, the oil displacement agent reacts with the reservoir rock, and there is a complex seepage-physical-chemical interaction in the porous medium. The rock wettability changes dynamically, which also determines the oil-water distribution state.

[0003] The capillary pressure curve is an important parameter that reflects the seepage characteristics of multiphase fluids in porous media, and its changing trend is affected by parameters such as rock wettability and fluid saturation. In general, rock wettability is considered to be constant, but in fact it is a dynamically changing parameter that is affected by factors such as rock chemical properties, fluid composition, reaction time with chemicals, reservoir temperature, and reservoir pressure. How to accurately characterize the dynamic changes of microscopic wettability and then accurately determine the core-scale capillary pressure curve is particularly important for revealing the infiltration and seepage control mechanism of nanofluids, surfactants, ion-matched water and other systems, and guiding the optimization design of oilfield development plans. At present, the core-scale capillary pressure curve only reflects the influence of fluid saturation, and does not consider the impact of dynamic changes in microscopic wetting. Summary of the invention

[0004] The object of the present invention is to provide a method for determining a capillary pressure curve taking into account the influence of dynamic changes in microscopic wetting during oil displacement by infiltration control.

[0005] The object of the present invention is to provide a method for determining a dynamic capillary pressure characterization model taking into account the influence of dynamic changes in microscopic wetting during infiltration-controlled oil displacement.

[0006] In order to achieve the above objectives, the present invention provides the following two technical solutions.

[0007] In a first aspect, the present invention provides a method for determining a capillary pressure curve in an infiltration-controlled oil displacement process, wherein the method comprises:

[0008] Construct capillary bundle geometry model;

[0009] Determine the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, and determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0010] A contact angle constitutive model is constructed to reflect the change of rock wettability during the process of oil displacement by wetting control, so as to constrain the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation.

[0011] Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation and the contact angle constitutive model, the capillary bundle geometric model is used to step-control the displacement pressure difference to perform multiple rounds of displacement-sucking flow simulation, and obtain the capillary pressure curves at different stages in the infiltration-regulated oil displacement process.

[0012] According to the method provided in the first aspect, preferably, constructing the capillary bundle geometric model includes:

[0013] Obtain the pore throat distribution characteristics of the target reservoir;

[0014] A capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir is constructed; wherein the capillary radius distribution in the capillary bundle model is characterized by a truncated Weibull distribution function;

[0015] More preferably, the capillary bundle model is a cylindrical capillary bundle model;

[0016] More preferably, the capillary radius distribution in the capillary bundle model is characterized by the following truncated Weibull distribution function:

[0017]

[0018] In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R av is the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model.

[0019] According to the method provided in the first aspect, preferably, respectively determining the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process, and determining the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation process includes:

[0020] Determine the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the target reservoir infiltration and oil displacement process; determine the oil-water interfacial tension during the target reservoir infiltration and oil displacement process;

[0021] Based on the rock contact angle in the initial wetting state during the target reservoir infiltration and oil displacement process, the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined;

[0022] The final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the rock contact angle in the final wetting state during the target reservoir infiltration control oil displacement process;

[0023] The oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the target reservoir infiltration and regulation of the oil-water interfacial tension during the oil displacement process.

[0024] According to the method provided in the first aspect, preferably, the contact angle constitutive model is a calculation model of the contact angle with respect to the contact reaction time;

[0025] More preferably, the contact angle constitutive model reflecting the change of rock wettability during the process of wetting regulation and oil displacement is:

[0026]

[0027]

[0028]

[0029] In the formula, θ m (·) is the contact angle at each position of the mth capillary during the displacement-sucking flow simulation; is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical on the rock pore wall, with a value of 0-1; C is a dimensionless parameter determined by the ratio of the adsorption and desorption rate constants during the wetting control oil displacement process, and is used to control the conversion speed from the initial wetting state to the final wetting state; χ m (t) is the normalized contact reaction time of the mth capillary at time t of displacement-sucking flow simulation; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition; is the interface position of the mth capillary at the time τ of displacement-sucking flow simulation, ranging from 0 to L; t is the duration of displacement-sucking flow simulation, ranging from 0 to T;

[0030] More preferably, the method further comprises the step of obtaining the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition:

[0031] Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, which is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition.

[0032] According to the method provided in the first aspect, preferably, stepwise controlling the displacement pressure difference to perform a round of displacement-sucking flow simulation includes:

[0033] 1) Fluid displacement process simulation steps:

[0034] ① Obtain the maximum threshold pressure P c max

[0035] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0036] ③ When ΔP<P c max Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined;

[0037] ④Gradually increase the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometric model until ΔP < P cmax If it is not established, the displacement simulation is completed;

[0038] 2) Fluid sucking process simulation steps:

[0039] ① Obtain the minimum threshold pressure P c min

[0040] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0041] ③ When ΔP>P c min Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined;

[0042] ④Gradually reduce the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until ΔP>P c min Not established to complete the sucking simulation;

[0043] 3) determining the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation;

[0044] More preferably, during multiple rounds of displacement-sucking flow simulation, after each round of displacement-sucking flow simulation is completed, the size of the contact angle in each capillary is determined based on the contact angle constitutive model, and the size of the contact angle in each capillary is updated, and then the above steps 1) to 3) are repeated to perform the next round of displacement-sucking flow simulation;

[0045] More preferably, the maximum threshold pressure P c max Not less than the maximum capillary pressure during displacement-sucking flow simulation;

[0046] More preferably, the minimum threshold pressure is no greater than the minimum capillary pressure during the displacement-sucking flow simulation;

[0047] More preferably, the capillary pressure P m Determined by the following formula:

[0048]

[0049] Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees.

[0050] According to the method provided in the first aspect, preferably, the contact angle is an oil phase contact angle.

[0051] According to the method provided in the first aspect, preferably, the capillary pressure curves at different stages in the infiltration-regulated oil displacement process are capillary pressure curves corresponding to different average contact reaction times in the infiltration-regulated oil displacement process.

[0052] According to the method provided in the first aspect, preferably, the method further comprises:

[0053] Determine the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the target reservoir infiltration and oil displacement process.

[0054] The technical solution of the first aspect of the present invention creatively constrains the contact angle during the flow simulation of the displacement-sucking process through a constitutive model that reflects the changes in rock wettability during the wetting-regulated oil recovery process, and obtains the capillary pressure curves of each stage in the wetting-regulated oil recovery process by utilizing the flow simulation of the displacement-sucking process. These capillary pressure curves take into account the influence of the dynamic changes in microscopic wetting during the wetting-regulated oil recovery process.

[0055] In a second aspect, the present invention provides a method for determining a dynamic capillary pressure characterization model in an infiltration-controlled oil displacement process, wherein the method comprises:

[0056] Obtain capillary pressure data at different stages of the target reservoir infiltration and oil displacement process;

[0057] Based on the capillary pressure data of different stages in the process of infiltration-controlled oil recovery in the target reservoir, a dynamic capillary pressure characterization model in the process of infiltration-controlled oil recovery was fitted.

[0058] According to the method provided in the second aspect, preferably, the dynamic capillary pressure characterization model in the infiltration regulation oil displacement process is:

[0059] P c =(1-ω)P cst,in +ωP c st,f

[0060]

[0061] Where P c st,in The capillary pressure in the initial wetting state during the oil displacement process is regulated by infiltration; P c st,f is the capillary pressure in the final wetting state during the oil displacement process; ω is the weight coefficient; is the uniform average contact reaction time, with a value of 0-1; S w is the oil phase fluid saturation; β2 is the dimensionless fitting coefficient.

[0062] According to the method provided in the second aspect, preferably, obtaining capillary pressure data at different stages in the process of oil displacement by infiltration control of the target reservoir includes:

[0063] Construct capillary bundle geometry model;

[0064] Determine the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, and determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0065] A contact angle constitutive model is constructed to reflect the change of rock wettability during the process of oil displacement by wetting control, so as to constrain the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation.

[0066] Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation and the contact angle constitutive model, the capillary bundle geometric model is used to step-control the displacement pressure difference to perform multiple rounds of displacement-sucking flow simulation, and obtain the capillary pressure curves at different stages in the infiltration-regulated oil displacement process.

[0067] According to the method provided in the second aspect, preferably, constructing the capillary bundle geometric model includes:

[0068] Obtain the pore throat distribution characteristics of the target reservoir;

[0069] A capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir is constructed; wherein the capillary radius distribution in the capillary bundle model is characterized by a truncated Weibull distribution function;

[0070] More preferably, the capillary bundle model is a cylindrical capillary bundle model.

[0071] More preferably, the capillary radius distribution in the capillary bundle model is characterized by the following truncated Weibull distribution function:

[0072]

[0073] In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R av is the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model.

[0074] According to the method provided in the second aspect, preferably, respectively determining the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process, and determining the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation process includes:

[0075] Determine the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the target reservoir infiltration and oil displacement process; determine the oil-water interfacial tension during the target reservoir infiltration and oil displacement process;

[0076] Based on the rock contact angle in the initial wetting state during the target reservoir infiltration and oil displacement process, the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined;

[0077] The final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the rock contact angle in the final wetting state during the target reservoir infiltration control oil displacement process;

[0078] The oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the target reservoir infiltration and regulation of the oil-water interfacial tension during the oil displacement process.

[0079] According to the method provided in the second aspect, preferably, the contact angle constitutive model is a calculation model of the contact angle with respect to the contact reaction time;

[0080] According to the method provided in the second aspect, preferably, the contact angle constitutive model reflecting the change of rock wettability during the process of wetting regulation and oil displacement is:

[0081]

[0082]

[0083]

[0084] In the formula, θ m(·) is the contact angle at each position of the mth capillary during the displacement-sucking flow simulation; is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical on the rock pore wall, with a value of 0-1; C is a dimensionless parameter determined by the ratio of the adsorption and desorption rate constants during the wetting control oil displacement process, and is used to control the conversion speed from the initial wetting state to the final wetting state; χ m (t) is the normalized contact reaction time of the mth capillary at time t of displacement-sucking flow simulation; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition that the contact angle of each capillary is the initial contact angle; is the interface position of the mth capillary at the time τ of displacement-sucking flow simulation, ranging from 0 to L; t is the duration of displacement-sucking flow simulation, ranging from 0 to T;

[0085] More preferably, the method further comprises the step of obtaining the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition:

[0086] Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, which is the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition of the initial contact angle.

[0087] According to the method provided in the second aspect, preferably, stepwise controlling the displacement pressure difference to perform a round of displacement-sucking flow simulation includes:

[0088] 1) Fluid displacement process simulation steps:

[0089] ① Obtain the maximum threshold pressure P c max

[0090] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0091] ③ When ΔP<P c max Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined;

[0092] ④Gradually increase the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometric model until ΔP < P c max If it is not established, the displacement simulation is completed;

[0093] 2) Fluid sucking process simulation steps:

[0094] ① Obtain the minimum threshold pressure P c min

[0095] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0096] ③ When ΔP>P c min Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined;

[0097] ④Gradually reduce the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until ΔP>P c min Not established to complete the sucking simulation;

[0098] 3) determining the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation;

[0099] More preferably, during multiple rounds of displacement-sucking flow simulation, after each round of displacement-sucking flow simulation is completed, the size of the contact angle in each capillary is determined based on the contact angle constitutive model, and the size of the contact angle in each capillary is updated, and then the above steps 1) to 3) are repeated to perform the next round of displacement-sucking flow simulation;

[0100] More preferably, the maximum threshold pressure P c max Not less than the maximum capillary pressure during displacement-sucking flow simulation;

[0101] More preferably, the minimum threshold pressure is no greater than the minimum capillary pressure during the displacement-sucking flow simulation;

[0102] More preferably, the capillary pressure P m Determined by the following formula:

[0103]

[0104] Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees.

[0105] According to the method provided in the second aspect, preferably, the contact angle is an oil phase contact angle.

[0106] According to the method provided in the second aspect, preferably, the capillary pressure data at different stages in the infiltration-regulated oil displacement process is the capillary pressure data corresponding to different average contact reaction times in the infiltration-regulated oil displacement process.

[0107] According to the method provided in the second aspect, preferably, the method further comprises:

[0108] Determine the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the target reservoir infiltration and oil displacement process.

[0109] The technical solution of the second aspect of the present invention creatively obtains a dynamic capillary pressure characterization model in the infiltration-regulated oil recovery process based on the capillary pressure data fitting at different stages in the infiltration-regulated oil recovery process. The model takes into account the influence of dynamic changes in microscopic wetting in the infiltration-regulated oil recovery process.

[0110] The technical solution provided by the present invention is applicable to low-permeability-tight oil, shale oil, and marine carbonate oil reservoirs. The method is easy to implement and the prediction results are highly accurate. It can provide a basis for the optimization design of infiltration control oil recovery schemes, development dynamic law analysis, and production optimization control for this type of complex oil reservoirs. The technical solution provided by the present invention solves the technical problem that the traditional capillary pressure theoretical model cannot reflect the influence of dynamic wetting changes, resulting in low accuracy of numerical simulation results. In addition, the technical solution provided by the present invention is not limited to infiltration control oil recovery systems such as nanofluids, surfactants, and ion-matched water, but can also be applied to other new technologies for improving recovery that can cause wetting changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Figure 1 A flow chart of a method for determining a capillary pressure curve in an infiltration-controlled oil displacement process provided in one embodiment of the present invention.

[0112] Figure 2 A flow chart of a method for determining a dynamic capillary pressure characterization model in an infiltration-controlled oil recovery process provided by an embodiment of the present invention.

[0113] Figure 3 It is a capillary pressure curve diagram at different stages of the infiltration regulation oil displacement process in Example 1 of the present invention.

[0114] Figure 4 This is a graph of capillary contact angles of various sizes at different stages during the infiltration and regulation oil displacement process in Example 1 of the present invention.

[0115] Figure 5 It is a comparison diagram of the capillary pressure curve obtained by using the dynamic capillary pressure characterization model in Example 1 of the present invention and the capillary pressure curve obtained by displacement-sucking flow simulation. DETAILED DESCRIPTION

[0116] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0117] See also Figure 1 A specific embodiment of the present invention provides a method for determining a capillary pressure curve during infiltration and oil displacement, wherein the method comprises:

[0118] Step S1: constructing a capillary bundle geometric model;

[0119] Step S2: respectively determining the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process, and determining the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation process;

[0120] Step S3: constructing a contact angle constitutive model that reflects the change in rock wettability during the infiltration-controlled oil displacement process, so as to constrain the size of each capillary contact angle in the capillary bundle geometric model during the displacement-sucking flow simulation process;

[0121] Step S4: Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, and the contact angle constitutive model, the capillary bundle geometric model is used to control the displacement pressure difference in a stepwise manner to perform multiple rounds of displacement-sucking flow simulation, and obtain the capillary pressure curves at different stages in the infiltration-regulated oil displacement process.

[0122] Further, in step S1, constructing the capillary bundle geometric model includes:

[0123] Step S11: obtaining the pore throat distribution characteristics of the target reservoir;

[0124] Among them, the pore throat distribution characteristics of the target reservoir can be determined by low-field nuclear magnetic resonance T2 spectrum analysis of actual rock samples of the target reservoir; in a specific implementation, actual rock samples at the target position of the target reservoir are drilled, the rock samples are deoiled and dried, and the rock samples after drying are tested by low-field nuclear magnetic resonance T2 spectrum. The pore throat distribution characteristics including the minimum pore throat radius, the maximum pore throat radius, the average pore throat radius and the pore throat radius distribution curve are determined based on the low-field nuclear magnetic resonance T2 spectrum obtained by the test;

[0125] Step S12: constructing a capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir; wherein the capillary radius distribution in the capillary bundle model is characterized by a truncated Weibull distribution function;

[0126] Furthermore, the capillary bundle model is a cylindrical capillary bundle model.

[0127] Furthermore, the capillary radius distribution in the capillary bundle model is characterized by the following truncated Weibull distribution function:

[0128]

[0129] In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R avis the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model.

[0130] Further, in step S2, the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation are determined respectively, and the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation is determined, including:

[0131] Step S21: determining the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the target reservoir infiltration and regulation oil displacement process; determining the oil-water interfacial tension during the target reservoir infiltration and regulation oil displacement process;

[0132] Among them, the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the infiltration and regulation of oil displacement of the target reservoir can be determined by testing the rock surface contact angle before and after the infiltration and regulation of oil displacement for the target reservoir rock sample; in a specific implementation manner, the rock surface contact angle test is carried out before and after the infiltration and regulation of oil displacement for the target reservoir rock sample, and then the rock surface contact angles before and after the infiltration and regulation of oil displacement obtained by the test are used as the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the infiltration and regulation of oil displacement of the target reservoir, respectively;

[0133] Among them, the oil-water interfacial tension during the oil displacement process of the target reservoir can be determined by performing an oil-water interfacial tension test on the target reservoir rock sample; in a specific implementation, an oil-water interfacial tension test is performed on the target reservoir rock sample, and the oil-water interfacial tension obtained by the test is used as the oil-water interfacial tension during the oil displacement process of the target reservoir;

[0134] Step S22: determining the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process based on the rock contact angle in the initial wetting state during the target reservoir infiltration control oil displacement process;

[0135] Among them, the rock contact angle in the initial wetting state during the target reservoir infiltration and oil displacement process can be used as the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process;

[0136] Step S23: determining the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process based on the rock contact angle in the final wetting state during the target reservoir infiltration control oil displacement process;

[0137] Among them, the rock contact angle in the final wetting state during the oil displacement process of the target reservoir infiltration control can be used as the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0138] Step S24: determining the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation based on the oil-water interfacial tension in the target reservoir infiltration control oil displacement process;

[0139] Among them, the oil-water interfacial tension in the target reservoir wetting and oil displacement process can be used as the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation.

[0140] Further, in step S3, the contact angle constitutive model is a calculation model of the contact angle with respect to the contact reaction time;

[0141] Furthermore, the contact angle constitutive model reflecting the change of rock wettability during oil displacement is:

[0142]

[0143]

[0144]

[0145] In the formula, θ m (·) is the contact angle at each position of the mth capillary during the displacement-sucking flow simulation (i.e., the normalized contact reaction time of the mth capillary is χ m The contact angle at each position at time t, i.e., the contact angle at each position of the mth capillary at time t in the displacement-sucking flow simulation); is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical agent on the rock pore wall, with a value of 0-1; C is a dimensionless parameter determined by the ratio of the adsorption rate constant to the desorption rate constant during the wetting control oil displacement process (in a specific embodiment, it is equal to the ratio of the adsorption rate constant to the desorption rate constant during the wetting control oil displacement process), and is used to control the conversion speed from the initial wetting state to the final wetting state; χ m (t) is the normalized contact reaction time of the mth capillary at time t of displacement-sucking flow simulation; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition; is the interface position of the mth capillary at the time τ of the displacement-sucking flow simulation (i.e., the function of the interface position changing with the displacement-sucking flow simulation duration), ranging from 0 to L; t is the displacement-sucking flow simulation duration, ranging from 0 to T;

[0146] Among them, for capillaries with different radius distributions, the contact reaction time of the displacement-sucking flow simulation is significantly different (in the above model, the normalized contact reaction time χ m To reflect), the wetting state of the capillary bundles with different radius distributions is non-uniform;

[0147] The interface position of the mth capillary at the time τ in the displacement-sucking flow simulation can be determined by using a simulation method in the art; for example, the interface movement position can be characterized by using the seepage velocity × time, which can be solved in real time by integral calculation in the displacement-sucking flow simulation;

[0148] Furthermore, before performing step S4, the method further comprises the step of obtaining the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition of the initial contact angle of each capillary:

[0149] Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, which is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition.

[0150] The contact angle constitutive model provided in the preferred technical method that reflects the change in rock wettability during the infiltration and regulation of oil recovery can effectively reflect the dynamic change mechanism of microscopic wetting during the infiltration and regulation of oil recovery by chemical agents such as nanofluids, surfactants, and ion-matched water.

[0151] Furthermore, the displacement pressure difference is controlled in stages to perform a displacement-sucking flow simulation including:

[0152] 1) Fluid displacement process simulation steps:

[0153] ① Obtain the maximum threshold pressure P c max

[0154] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0155] ③ When ΔP<P c max Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined;

[0156] ④Gradually increase the pressure P of the water phase fluid at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometric model until ΔP < P c max If it is not established, the displacement simulation is completed;

[0157] 2) Fluid sucking process simulation steps:

[0158] ① Obtain the minimum threshold pressure P c min

[0159] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0160] ③ When ΔP>P c min Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined;

[0161] ④Gradually reduce the pressure P of the water phase fluid at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until ΔP>P c min Not established to complete the sucking simulation;

[0162] 3) determining the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation;

[0163] Furthermore, during multiple rounds of displacement-sucking flow simulation, after each round of displacement-sucking flow simulation is completed, the size of the contact angle in each capillary is determined based on the contact angle constitutive model, and the size of the contact angle in each capillary is updated, and then the above steps 1) to 3) are repeated to perform the next round of displacement-sucking flow simulation;

[0164] Furthermore, the maximum threshold pressure P c max Not less than the maximum capillary pressure during displacement-sucking flow simulation;

[0165] Furthermore, the minimum threshold pressure is no greater than the minimum capillary pressure during the displacement-sucking flow simulation;

[0166] Furthermore, the capillary pressure P m Determined by the following formula:

[0167]

[0168] Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees;

[0169] The average contact reaction time of each capillary can be obtained by weighted average of the contact reaction time of each capillary.

[0170] Furthermore, the contact angle is the oil phase contact angle.

[0171] Furthermore, the capillary pressure curves at different stages in the infiltration-controlled oil displacement process are capillary pressure curves corresponding to different average contact reaction times in the infiltration-controlled oil displacement process.

[0172] Furthermore, the method further comprises:

[0173] Determine the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the oil displacement process of the target reservoir under infiltration control;

[0174] Among them, the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the infiltration and regulation oil displacement process of the target reservoir can be determined by performing mercury injection tests on the target reservoir rock samples before and after the infiltration and regulation oil displacement; in a specific implementation method, mercury injection tests are carried out on the target reservoir rock samples before and after the infiltration and regulation oil displacement, and the capillary pressure curves before and after the infiltration and regulation oil displacement obtained by the tests are used as the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the infiltration and regulation oil displacement process of the target reservoir, respectively.

[0175] Among them, the capillary pressure curves at different stages in the process of infiltration-controlled oil displacement are obtained based on the results of multiple rounds of displacement-sucking flow simulation based on step-by-step control of the displacement pressure difference, which can be specifically carried out in a conventional manner in the field.

[0176] See also Figure 2 The embodiment of the present invention also provides a method for determining a dynamic capillary pressure characterization model in an infiltration-controlled oil displacement process, wherein the method comprises:

[0177] Step A1: obtaining capillary pressure data at different stages of the target reservoir infiltration control oil displacement process;

[0178] Step A2: Based on the capillary pressure data at different stages of the target reservoir infiltration-controlled oil recovery process, a dynamic capillary pressure characterization model in the infiltration-controlled oil recovery process is fitted.

[0179] Furthermore, the dynamic capillary pressure characterization model in the infiltration regulation oil displacement process is:

[0180]

[0181]

[0182] Where P c st,in The capillary pressure in the initial wetting state during the oil displacement process is regulated by infiltration; P c st,f is the capillary pressure in the final wetting state during the oil displacement process; ω is the weight coefficient; is the uniform average contact reaction time, with a value of 0-1; S w is the oil phase fluid saturation; β2 is the dimensionless fitting coefficient.

[0183] Furthermore, the capillary pressure data at different stages of the target reservoir infiltration and oil displacement process are obtained, including:

[0184] Step A11: constructing a capillary bundle geometric model;

[0185] Step A12: respectively determining the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process, and determining the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation process;

[0186] Step A13: constructing a contact angle constitutive model that reflects the change in rock wettability during the infiltration-controlled oil displacement process, so as to constrain the size of each capillary contact angle in the capillary bundle geometric model during the displacement-sucking flow simulation process;

[0187] Step A14: Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, and the contact angle constitutive model, the capillary bundle geometric model is used to control the displacement pressure difference in a stepwise manner to perform multiple rounds of displacement-sucking flow simulation, and obtain the capillary pressure curves at different stages in the infiltration-regulated oil recovery process.

[0188] Furthermore, in step A11, constructing the capillary bundle geometric model includes:

[0189] Step A111: obtaining pore throat distribution characteristics of the target reservoir;

[0190] Step A112: constructing a capillary bundle model capable of describing the pore throat distribution characteristics of the target reservoir; wherein the capillary radius distribution in the capillary bundle model is characterized by a truncated Weibull distribution function;

[0191] Furthermore, the capillary bundle model is a cylindrical capillary bundle model.

[0192] Furthermore, the capillary radius distribution in the capillary bundle model is characterized by the following truncated Weibull distribution function:

[0193]

[0194] In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R av is the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model.

[0195] Furthermore, in step A12, the initial contact angle and the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation are determined respectively, and the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation is determined, including:

[0196] Step A121: determining the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the target reservoir infiltration and oil displacement process; determining the oil-water interfacial tension during the target reservoir infiltration and oil displacement process;

[0197] Step A122: determining the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process based on the rock contact angle in the initial wetting state during the target reservoir infiltration control oil displacement process;

[0198] Step A123: determining the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation process based on the rock contact angle in the final wetting state during the target reservoir infiltration control oil displacement process;

[0199] Step A124: Determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation based on the oil-water interfacial tension in the target reservoir infiltration control oil-water interfacial tension during the displacement.

[0200] Furthermore, in step A13, the contact angle constitutive model is a calculation model of the contact angle with respect to the contact reaction time;

[0201] Furthermore, the contact angle constitutive model that reflects the change of rock wettability during oil displacement is:

[0202]

[0203]

[0204]

[0205] In the formula, θ m (·) is the contact angle at each position of the mth capillary during the displacement-sucking flow simulation; is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical on the rock pore wall, with a value of 0-1; C is a dimensionless parameter determined by the ratio of the adsorption and desorption rate constants during the wetting control oil displacement process, and is used to control the conversion speed from the initial wetting state to the final wetting state; χ m (t) is the normalized contact reaction time of the mth capillary at time t of displacement-sucking flow simulation; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition; is the interface position in the mth capillary at the time τ of displacement-sucking flow simulation, ranging from 0 to L; t is the duration of displacement-sucking flow simulation, ranging from 0 to T;

[0206] Furthermore, before performing step A14, the method further includes the step of obtaining the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition:

[0207] Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, that is, the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition that each capillary contact angle is the initial contact angle.

[0208] Furthermore, the displacement pressure difference is controlled in stages to perform a displacement-sucking flow simulation including:

[0209] 1) Fluid displacement process simulation steps:

[0210] ① Obtain the maximum threshold pressure P c max

[0211] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0212] ③ When ΔP<P c max Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined;

[0213] ④Gradually increase the pressure P of the water phase fluid at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometric model until ΔP < P c max If it is not established, the displacement simulation is completed;

[0214] 2) Fluid sucking process simulation steps:

[0215] ① Obtain the minimum threshold pressure P c min

[0216] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0217] ③ When ΔP>P c min Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined;

[0218] ④Gradually reduce the pressure P of the water phase fluid at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until ΔP>P c min Not established to complete the sucking simulation;

[0219] 3) determining the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation;

[0220] Furthermore, in the process of multiple rounds of displacement-sucking flow simulation, after each round of displacement-sucking flow simulation is completed, the size of the contact angle in each capillary is determined based on the contact angle constitutive model, and the size of the contact angle in each capillary is updated, and then the above steps 1) to 3) are repeated to perform the next round of displacement-sucking flow simulation;

[0221] Furthermore, the maximum threshold pressure P c max Not less than the maximum capillary pressure during displacement-sucking flow simulation;

[0222] Furthermore, the minimum threshold pressure is no greater than the minimum capillary pressure during the displacement-sucking flow simulation;

[0223] Furthermore, the capillary pressure P m Determined by the following formula:

[0224]

[0225] Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees;

[0226] The average contact reaction time of each capillary can be obtained by weighted average of the contact reaction time of each capillary.

[0227] Furthermore, the contact angle is the oil phase contact angle.

[0228] Furthermore, each capillary pressure curve in the infiltration-controlled oil displacement process is a capillary pressure curve corresponding to different average contact reaction times in the infiltration-controlled oil displacement process.

[0229] Furthermore, the method further comprises:

[0230] Determine the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the target reservoir infiltration and oil displacement process.

[0231] The method for obtaining the dynamic capillary pressure characterization model during the infiltration-controlled oil recovery process can be used to determine the dynamic capillary pressure curve during the infiltration-controlled oil recovery process.

[0232] Among them, the capillary pressure curves at different stages in the process of infiltration-controlled oil displacement are obtained based on the results of multiple rounds of displacement-sucking flow simulation based on step-by-step control of the displacement pressure difference, which can be specifically carried out in a conventional manner in the field.

[0233] Example 1

[0234] Taking a low permeability rock sample of a multimodal carbonate reservoir in a certain area as an example, the method for determining the capillary pressure curve in the process of infiltration regulation and oil recovery and the method for determining the dynamic capillary pressure characterization model of the present invention are described; specifically, the following steps are followed:

[0235] 1. Determine the pore throat distribution characteristics of the target reservoir, construct a capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir, and characterize the capillary radius distribution in the capillary bundle model by using the truncated Weibull distribution function;

[0236] Specifically, actual rock samples at the target position of the target reservoir are drilled, the rock samples are deoiled and dried, low-field nuclear magnetic resonance T2 spectrum test is performed on the dried rock samples, and the pore throat distribution characteristics including the minimum pore throat radius (see Table 1), the maximum pore throat radius (see Table 1), the average pore throat radius (see Table 1) and the pore throat radius distribution curve are determined based on the low-field nuclear magnetic resonance T2 spectrum obtained in the test;

[0237] Then, a cylindrical capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir is constructed, and the capillary radius distribution in the capillary bundle model is characterized by the truncated Weibull distribution function as shown below:

[0238]

[0239] In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R av is the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model;

[0240] The number and length of capillaries in the capillary bundle model are shown in Table 1.

[0241] 2. Determine the pore throat distribution characteristics of the target reservoir, the rock oil phase contact angle in the initial wetting state and the rock oil phase contact angle in the final wetting state during the infiltration and regulation of oil displacement, the capillary pressure curve in the initial wetting state and the capillary pressure curve in the final wetting state during the infiltration and regulation of oil displacement, and the oil-water interfacial tension; determine the initial oil phase contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation based on the rock oil phase contact angle in the initial wetting state during the infiltration and regulation of oil displacement of the target reservoir (see Table 1); determine the final oil phase contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation based on the rock contact angle in the final wetting state during the infiltration and regulation of oil displacement of the target reservoir (see Table 1); determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation based on the oil-water interfacial tension during the infiltration and regulation of oil displacement of the target reservoir (see Table 1);

[0242] Specifically: for the target reservoir rock samples, the rock surface contact angle tests are carried out before and after the infiltration and regulation oil displacement, and then the rock surface contact angles before and after the infiltration and regulation oil displacement obtained by the tests are used as the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the infiltration and regulation oil displacement of the target reservoir, respectively; the rock contact angle in the initial wetting state during the infiltration and regulation oil displacement of the target reservoir is used as the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation; the rock contact angle in the final wetting state during the infiltration and regulation oil displacement of the target reservoir is used as the final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0243] For the target reservoir rock samples, the oil-water interface tension test is carried out, and the oil-water interface tension obtained by the test is used as the oil-water interface tension in the process of oil displacement by wetting and regulating the target reservoir; the oil-water interface tension in the process of oil displacement by wetting and regulating the target reservoir is used as the oil-water interface tension in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0244] For the target reservoir rock samples, mercury injection tests were carried out before and after the infiltration and regulation flooding, and the capillary pressure curves before and after the infiltration and regulation flooding obtained were used as the capillary pressure curves of the target reservoir in the initial wetting state during the infiltration and regulation flooding process (see Figure 3 ) and the capillary pressure curve in the final wetting state (see Figure 3 ).

[0245] Table 1

[0246] parameter Value unit parameter Value unit Oil-water interfacial tension 7.2 mN / m Number of capillaries 500 indivual Minimum pore throat radius 6.0 μm Maximum pore throat radius 40.0 μm Final oil phase contact angle 80 Spend Initial oil phase contact angle 0.0 Spend Oil phase viscosity 1.5 mPa·s Water phase viscosity 1.5 mPa·s Capillary length 0.001 m Average pore radius 23.0 μm

[0247] 3. Construct a contact angle constitutive model that reflects the change in rock wettability during the process of oil displacement by wetting control, so as to constrain the size of the capillary contact angles in the capillary bundle geometric model during the displacement-sucking flow simulation;

[0248] Specifically: Construct the following contact angle constitutive model to reflect the change of rock wettability during the process of oil displacement regulated by infiltration:

[0249]

[0250]

[0251]

[0252] In the formula, θ m (·) is the contact angle at each position after the mth capillary interface position during the displacement-sucking flow simulation; is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical agent on the rock pore wall, with a value of 0-1; C is a dimensionless parameter, which is equal to the ratio of the adsorption and desorption rate constants during the wetting control oil displacement process, and is used to control the conversion speed from the initial wetting state to the final wetting state. In this embodiment, the value is 3×10 -3 ; m (t) is the duration of displacement-sucking flow simulation t, the normalized contact reaction time of the mth capillary; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition that the contact angle of each capillary is the initial contact angle; is the interface position of the displacement-sucking flow simulation in the mth capillary for τ time, ranging from 0 to L; t is the displacement-sucking flow simulation time, ranging from 0 to T;

[0253] The time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition is determined by the following method:

[0254] Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model of this embodiment is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, which is the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition of the initial contact angle.

[0255] 4. Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, and the constitutive model of oil-water interfacial tension and contact angle in the capillary bundle geometric model during the displacement-sucking flow simulation, the capillary bundle geometric model is used to control the displacement pressure difference in stages to perform multiple rounds of displacement-sucking flow simulation, obtain the capillary pressure data at different stages in the infiltration-controlled oil displacement process, and obtain the capillary pressure curves at different stages in the infiltration-controlled oil displacement process;

[0256] Among them, the step-by-step control of displacement pressure difference for multiple rounds of displacement-sucking flow simulation includes:

[0257] 1) Fluid displacement process simulation steps:

[0258] ① Obtain the maximum threshold pressure P c max

[0259] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=Pl res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0260] ③ When ΔP<P c max Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined;

[0261] ④Gradually increase the water phase fluid pressure P at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometric model until ΔP < P c max If it is not established, the displacement simulation is completed;

[0262] ⑤ Determine the characteristic duration and average contact reaction time of displacement simulation;

[0263] 2) Fluid sucking process simulation steps:

[0264] ① Obtain the minimum threshold pressure P c min

[0265] ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, ΔP=P l res -P r res ; where P l res , P r res are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively;

[0266] ③ When ΔP>P c min Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined;

[0267] ④Gradually reduce the water phase fluid pressure P at the injection end l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until ΔP>P c min Not established to complete the sucking simulation;

[0268] ⑤ Determine the characteristic duration of sucking simulation and the average contact reaction time;

[0269] 3) determining the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation;

[0270] 4) determining the size of the contact angle in each capillary based on the contact angle constitutive model, and updating the size of the contact angle in each capillary, and then repeating the above steps 1) to 3) to perform the next round of displacement-sucking flow simulation;

[0271] Among them, the maximum threshold pressure P c max is the maximum capillary pressure during displacement-sucking flow simulation; the minimum threshold pressure P c min is the minimum capillary pressure during displacement-sucking flow simulation;

[0272] Where, capillary pressure P m Determined by the following formula:

[0273]

[0274] Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees.

[0275] The capillary pressure curves at different stages of the infiltration-controlled oil displacement process are determined as follows: Figure 3 As shown in the figure, it can be seen that the contact reaction time with the chemical agent has a significant effect on the capillary pressure curve. With the increase of contact reaction time, the capillary pressure at the bound water saturation remains basically unchanged, and eventually approaches the capillary pressure value of the endpoint wetting state; the dynamic change of the contact angle during the wetting regulation oil displacement process is shown in the figure. Figure 4 As shown, it can be seen that the contact angle has a good correlation with the capillary radius and the contact reaction time, indicating that in addition to the saturation of the wetting phase fluid, the length of the contact reaction time will also significantly affect the size of the capillary pressure.

[0276] 5. Based on the capillary pressure data at different stages of the target reservoir infiltration control oil recovery process, a dynamic capillary pressure characterization model in the infiltration control oil recovery process is fitted;

[0277] The dynamic capillary pressure characterization model finally fitted is:

[0278]

[0279] Where P c st,in The capillary pressure in the initial wetting state during the oil displacement process is regulated by infiltration; P c st,f is the capillary pressure in the final wetting state during the infiltration and oil displacement process; χ is the average contact reaction time; S w is the oil phase fluid saturation;

[0280] In order to verify the accuracy of the dynamic capillary pressure calculation model, the dynamic capillary pressure in the process of infiltration-controlled oil displacement was determined using the dynamic capillary pressure calculation model. The dynamic capillary pressure curve in the process of infiltration-controlled oil displacement determined using the dynamic capillary pressure calculation model was compared with the capillary pressure curve obtained by displacement-sucking flow simulation in step 4 (e.g. Figure 5 As shown), it can be seen that the dynamic capillary pressure characterization model established in the embodiment of the present invention can well match the displacement-sucking flow simulation results.

[0281] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining a capillary pressure curve during oil displacement by infiltration control, wherein: The method includes: Construct capillary bundle geometry model; Determine the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, and determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation; A contact angle constitutive model is constructed to reflect the change of rock wettability during the process of oil displacement by wetting control, so as to constrain the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation. Based on the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, and the contact angle constitutive model, the capillary bundle geometric model is used to control the displacement pressure difference in stages to perform multiple rounds of displacement-sucking flow simulation, and obtain the capillary pressure curves at different stages in the infiltration-controlled oil displacement process; Among them, constructing the capillary bundle geometric model includes: Obtain the pore throat distribution characteristics of the target reservoir; A capillary bundle model that can describe the pore throat distribution characteristics of the target reservoir is constructed; wherein the capillary radius distribution in the capillary bundle model is characterized by a truncated Weibull distribution function; The contact angle constitutive model reflecting the change of rock wettability during oil displacement by wetting control is: In the formula, θ m (·) is the contact angle of the mth capillary during displacement-sucking flow simulation; is the final contact angle of the mth capillary; is the initial contact angle of the mth capillary; is a dynamic parameter reflecting the degree of adsorption of the wetting control chemical on the rock pore wall, with a value of 0-1; C is a dimensionless parameter determined by the ratio of the adsorption and desorption rate constants during the wetting control oil displacement process, and is used to control the conversion speed from the initial wetting state to the final wetting state; χ m (t) is the duration of displacement-sucking flow simulation t, the normalized contact reaction time of the mth capillary; L is the length of a single capillary; T is the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition; is the interface position corresponding to the displacement-sucking flow simulation time τ of the mth capillary, which is between 0-L; t is the displacement-sucking flow simulation time, which is between 0-T.

2. The method according to claim 1, wherein: The capillary bundle model is a cylindrical capillary bundle model.

3. The method according to claim 1, wherein: The capillary radius distribution in the capillary bundle model is characterized by the following truncated Weibull distribution function: In the formula, R max is the maximum pore throat radius of the target reservoir; R min is the minimum pore throat radius of the target reservoir; R av is the average pore throat radius of the target reservoir; η is a dimensionless parameter; f(R) is the distribution frequency of capillaries with a radius of R in the capillary bundle model.

4. The method according to claim 1, wherein: Determine the initial contact angle and final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation, and determine the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, including: Determine the rock contact angle in the initial wetting state and the rock contact angle in the final wetting state during the target reservoir infiltration and oil displacement process; determine the oil-water interfacial tension during the target reservoir infiltration and oil displacement process; Based on the rock contact angle in the initial wetting state during the target reservoir infiltration and oil displacement process, the initial contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined; The final contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the rock contact angle in the final wetting state during the target reservoir infiltration control oil displacement process; The oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation is determined based on the target reservoir infiltration and regulation of the oil-water interfacial tension during the oil displacement process.

5. The method according to claim 1, wherein: The method further includes the step of obtaining the time for all capillaries to perform a round of displacement-sucking flow simulation under the initial contact angle condition: Based on the oil-water interfacial tension in the capillary bundle geometric model during the displacement-sucking flow simulation, the contact angle of each capillary in the capillary bundle geometric model during the displacement-sucking flow simulation is the initial contact angle, and the capillary bundle geometric model is used to step-control the displacement pressure difference to perform a round of displacement-sucking flow simulation, and the time for all capillaries to perform a complete displacement-sucking flow simulation is obtained, which is the time for all capillaries to perform a round of displacement-sucking flow simulation under the condition of the initial contact angle.

6. The method according to claim 5, wherein: Step-by-step control of displacement pressure difference to conduct a round of displacement-sucking flow simulation includes: 1) Fluid displacement process simulation steps: ①Get the maximum threshold pressure ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, Where P l res , are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively; ③In Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it less than the displacement pressure difference ΔP? If so, the displacement simulation is performed on the capillary until a stable state is reached; the average saturation of the capillary bundle geometric model is determined; ④Gradually increase the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform displacement simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until If it does not hold, the displacement simulation is completed; 2) Fluid sucking process simulation steps: ① Obtain the minimum threshold pressure ② Obtain the displacement pressure difference ΔP between the water phase and the oil phase fluid, Where P l res , are the pressures of the water phase fluid at the inlet end and the oil phase fluid at the outlet end of the capillary bundle model, respectively; ③In Under the condition, for each capillary in the capillary bundle geometric model, determine the capillary pressure P of the capillary m Is it greater than the displacement pressure difference ΔP? If so, the capillary is subjected to a sucking simulation until a steady state is reached; the average saturation of the capillary bundle geometric model is determined; ④Gradually reduce the pressure P of the water phase fluid at the inlet l res Repeat steps ②-③ to update the displacement pressure difference ΔP and perform suction simulation under the updated displacement pressure difference ΔP to determine the average saturation of the capillary bundle geometry model until Not established to complete the sucking simulation; 3) Determine the contact reaction time of each capillary and the average contact reaction time of each capillary during the displacement-sucking flow simulation.

7. The method according to claim 6, wherein: During multiple rounds of displacement-sucking flow simulation, after each round of displacement-sucking flow simulation is completed, the size of the contact angle in each capillary is determined based on the contact angle constitutive model, and the size of the contact angle in each capillary is updated, and then the above steps 1) to 3) are repeated to perform the next round of displacement-sucking flow simulation.

8. The method according to claim 6, wherein: Maximum threshold pressure Not less than the maximum capillary pressure during displacement-sucking flow simulation; The minimum threshold pressure is no greater than the minimum capillary pressure during the displacement-sucking flow simulation; Capillary pressure P m Determined by the following formula: Where P m is the capillary pressure, in Pa; σ is the oil-water interfacial tension, in mN / m; R m is the inner diameter of the mth capillary, in μm; θ m is the contact angle of the mth capillary, in degrees.

9. The method according to claim 1, wherein: The capillary pressure curves at different stages of the infiltration-controlled oil displacement process are capillary pressure curves corresponding to different average contact reaction times during the infiltration-controlled oil displacement process; The capillary pressure data at different stages in the infiltration-controlled oil displacement process are capillary pressure data corresponding to different average contact reaction times in the infiltration-controlled oil displacement process.

10. A method for determining a dynamic capillary pressure characterization model in an infiltration-controlled oil displacement process, wherein: The method includes: Obtain capillary pressure data at different stages of the target reservoir infiltration and oil displacement process; Based on the capillary pressure data at different stages of the target reservoir infiltration-controlled oil recovery process, a dynamic capillary pressure characterization model in the infiltration-controlled oil recovery process is fitted; The dynamic capillary pressure characterization model in the process of oil displacement regulated by infiltration is: In the formula, To regulate the capillary pressure in the initial wetting state during oil displacement for infiltration; is the capillary pressure in the final wetting state during the oil displacement process; ω is the weight coefficient; is the uniform average contact reaction time, with a value of 0-1; S w is the oil phase fluid saturation; β2 is the dimensionless fitting coefficient; Among them, the capillary pressure data at different stages of the target reservoir infiltration and oil displacement process include: The capillary pressure curves at different stages in the infiltration-controlled oil displacement process are obtained according to the method for determining the capillary pressure curve in the infiltration-controlled oil displacement process according to any one of claims 1 to 9.

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