A method and apparatus for determining relative permeability based on diffusion

Abstract

The application provides a method and device for determining relative permeability based on diffusion, wherein the method comprises the following steps: determining an effective diffusion coefficient of CO2 gas in a saturated oil porous medium and an isothermal compressibility of the CO2 gas; determining a coefficient representing gas diffusion; calculating dimensionless cumulative oil production considering diffusion according to the effective diffusion coefficient of the CO2 gas in the saturated oil porous medium; obtaining oil content considering diffusion in the target core; and determining oil phase relative permeability and gas phase relative permeability of the target core according to the effective diffusion coefficient of the CO2 gas in the saturated oil porous medium, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion and the oil content considering diffusion. The above scheme solves the technical problems of high accuracy and low efficiency in the existing calculation of relative permeability, and achieves the technical effect of accurately and efficiently determining relative permeability.

Description

Technical Field

[0001] This application belongs to the field of oil and gas exploration technology, and in particular relates to a method and apparatus for determining relative permeability based on diffusion. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) technology is one of the important ways to reduce greenhouse gas emissions. CO2 injection into formations can lock in greenhouse gases, thereby reducing carbon emissions and improving oil recovery rates.

[0003] The underground flow of CO2-crude oil involves a complex seepage mechanism. The relative permeability curve of CO2-crude oil is fundamental to studying its underground seepage and is also crucial for subsequent numerical simulation studies. The determination of CO2-crude oil relative permeability mainly involves steady-state and unsteady-state methods. The unsteady-state method is widely used due to its simplicity and short measurement cycle. Currently, the unsteady-state method is often combined with the JBN method to calculate relative permeability; however, this method, in pursuit of computational simplicity, suffers from relatively low accuracy.

[0004] Existing methods for calculating the relative permeability of CO2-crude oil systems are generally applicable to CO2-crude oil systems in the presence of bound water. Specifically, this involves configuring live oil in an experimental setup and measuring its viscosity, CO2 solubility in the gas-bearing live oil, and CO2 solubility in formation water. Based on these measured parameters and displacement experiments, the relative permeability curve of CO2-crude oil at bound water saturation is obtained. However, this method involves complex experimental setups, cumbersome operation, and the fundamental calculation principle is a steady-state method, requiring the measurement of flow rates at steady-state times under different oil-gas ratios, which consumes a significant amount of time.

[0005] There are currently no effective solutions to the technical problems of low accuracy in existing unsteady-state methods and high operational complexity in steady-state methods. Summary of the Invention

[0006] The purpose of this application is to provide a method and apparatus for determining relative permeability based on diffusion, which can achieve the goal of accurately and efficiently determining relative permeability.

[0007] This application provides a method and apparatus for determining relative permeability based on diffusion, which is implemented as follows:

[0008] A method for determining relative permeability based on diffusion, the method comprising:

[0009] Determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in the target core in saturated oil porous media;

[0010] The coefficient representing the gas diffusion effect is determined based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas.

[0011] Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the dimensionless cumulative oil production considering diffusion is calculated.

[0012] Obtain the oil content in the target core considering diffusion effects;

[0013] Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil content considering diffusion, the relative permeability of the oil phase and the relative permeability of the gas phase in the target core are determined.

[0014] In one embodiment, the relative permeability of the oil phase and the relative permeability of the gas phase of the target core are determined based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, a coefficient representing gas diffusion, dimensionless cumulative oil production considering diffusion, and oil cut considering diffusion, including:

[0015] The relative permeability of the oil phase and the relative permeability of the gas phase are calculated using the following formula:

[0016]

[0017] Among them, K ro f represents the relative permeability of the oil phase. o (S g () indicates the oil content taking diffusion into account. This represents the dimensionless cumulative oil and gas production considering diffusion effects, where I represents the flow capacity ratio, and K... rg The gas phase relative permeability, m g Indicates gas phase viscosity, m o D represents the viscosity of the oil phase, and D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium. e The coefficient representing the gas diffusion effect.

[0018] In one embodiment, determining the effective diffusion coefficient of CO2 gas in a saturated oil porous medium within a target rock core includes:

[0019] The effective diffusion coefficient of CO2 gas in saturated oil porous media is calculated using the following formula:

[0020]

[0021] in,

[0022] Where D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and Kp V represents the slope of the fitted pressure drop curve. d r represents the gas volume excluding the core volume. o Z represents the radius of the target core, Z represents the gas compressibility coefficient, R represents the universal gas constant, T represents the temperature, and N represents the temperature. ￥ Dp represents the maximum mass of gas that can diffuse into the core. pg Z1 represents the pressure drop at time t, where t represents the diffusion time, p1 represents the initial pressure, p2 represents the equilibrium pressure, Z1 represents the compressibility factor of CO2 at pressure p1, Z2 represents the compressibility factor of CO2 at pressure p2, and V represents the gas volume.

[0023] In one implementation, determining the isothermal compressibility of CO2 gas includes:

[0024] The isothermal compressibility of CO2 gas is calculated using the following formula:

[0025]

[0026] Among them, C g The value represents the isothermal compressibility of CO2 gas, and P represents pressure.

[0027] In one embodiment, a coefficient representing the gas diffusion effect is determined based on the effective diffusion coefficient of CO2 gas in a saturated oil porous medium and the isothermal compressibility of CO2 gas, including:

[0028] Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas, the coefficient representing the gas diffusion effect is calculated according to the following formula:

[0029]

[0030] Among them, D e The coefficient representing gas diffusion, C g The isothermal compressibility of CO2 gas, m g S represents the gas phase viscosity, D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium, and S represents the gas phase viscosity. g The value represents the gas saturation, and K represents the permeability.

[0031] In one embodiment, the dimensionless cumulative oil production, taking into account diffusion, is calculated based on the effective diffusion coefficient of CO2 gas in a saturated oil porous medium, including:

[0032] The diffusion band length is calculated using the following formula based on the effective diffusion coefficient of CO2 gas in saturated oil porous media:

[0033]

[0034] Where X represents the diffusion zone length, D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and t represents the diffusion time;

[0035] Based on the length of the diffusion zone, combined with the cross-sectional area and porosity of the core, the volume of the diffusion zone is calculated using the following formula:

[0036] V d =A×X×f

[0037] Among them, V d The diffuse zone volume is represented by A, the cross-sectional area of ​​the core is represented by f, and the porosity is represented by f.

[0038] Based on the diffusion zone volume and the dimensionless cumulative oil production, the dimensionless cumulative oil production considering diffusion is calculated using the following formula:

[0039]

[0040] in, This represents the dimensionless cumulative oil production considering diffusion effects. This indicates the dimensionless cumulative oil production.

[0041] An apparatus for determining relative permeability based on diffusion includes:

[0042] The first determining module is used to determine the effective diffusion coefficient of CO2 gas in the saturated oil porous medium and the isothermal compressibility of CO2 gas in the target core.

[0043] The second determining module is used to determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas.

[0044] The calculation module is used to calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous media.

[0045] The acquisition module is used to obtain the oil content in the target core considering diffusion effects;

[0046] The third determination module is used to determine the relative permeability of the oil phase and the relative permeability of the gas phase of the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing the gas diffusion effect, the dimensionless cumulative oil production considering the diffusion effect, and the oil content considering the diffusion effect.

[0047] An electronic device includes a processor and a memory for storing processor-executable instructions, wherein the processor, when executing the instructions, implements the steps of the method described above.

[0048] A computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0049] A computer program product includes a computer program / instructions that, when executed by a processor, implement the steps of the above-described method.

[0050] The method and apparatus for determining relative permeability based on diffusion provided in this application determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in a saturated oil porous medium within a target core. Further, based on these parameters, a coefficient representing gas diffusion is determined. Then, based on the effective diffusion coefficient and isothermal compressibility of CO2 gas in the saturated oil porous medium, the dimensionless cumulative oil production considering diffusion is calculated. Finally, based on the effective diffusion coefficient, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil cut considering diffusion, the relative permeability of the oil phase and the relative permeability of the gas phase in the target core are determined. In other words, the diffusion coefficient, oil production, and oil cut are determined by considering the diffusion of CO2 gas between crude oils. The relative permeability of the oil phase and the relative permeability of the gas phase in the target core are then determined based on these parameters considering the diffusion of CO2 gas between crude oils. Because the diffusion of CO2 gas between crude oils is considered in the determination process, the results are more accurate. The above solution solves the technical problems of high accuracy and low efficiency in the existing calculation of relative permeability, and achieves the technical effect of accurately and efficiently determining relative permeability. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a flowchart of one embodiment of the method for determining relative penetration rate provided in this application;

[0053] Figure 2 This is a structural diagram of the pressure drop method measuring device provided in this application;

[0054] Figure 3 This is a schematic diagram of the pressure drop curve during the diffusion coefficient measurement process provided in this application;

[0055] Figure 4This is a schematic diagram of the apparatus for determining the relative permeability of CO2-crude oil using the unsteady-state method provided in this application;

[0056] Figure 5 This is a diagram showing the calculation results provided in this application;

[0057] Figure 6 This is a hardware structure block diagram of an electronic device for a method of determining relative penetration rate provided in this application;

[0058] Figure 7 This is a schematic diagram of the module structure of one embodiment of the relative penetration rate determination device provided in this application. Detailed Implementation

[0059] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0060] Given the inaccuracies of existing unsteady-state methods, primarily due to the neglect of the interaction between underground CO2 and crude oil, particularly the diffusion between CO2 and crude oil, the results contain errors in describing the actual reservoir seepage process. Therefore, the role of diffusion in accurately describing underground CO2-crude oil seepage needs to be considered when calculating relative permeability using unsteady-state methods. Based on this, this example presents a method for determining relative permeability to accurately describe the reservoir seepage process, providing a more precise reference and guidance for CO2-assisted oil recovery.

[0061] Figure 1 This is a flowchart of one embodiment of the method for determining relative permeability based on diffusion provided in this application. While this application provides method operation steps or apparatus structures as shown in the following embodiments or figures, more or fewer operation steps or module units may be included in the method or apparatus based on conventional or non-inventive effort. In steps or structures where there is no logically necessary causal relationship, the execution order of these steps or the module structure of the apparatus is not limited to the execution order or module structure described in the embodiments and figures of this application. When the method or module structure is applied in actual devices or terminal products, it can be executed sequentially or in parallel according to the method or module structure shown in the embodiments or figures (e.g., in a parallel processor or multi-threaded processing environment, or even a distributed processing environment).

[0062] Specifically, such as Figure 1As shown, the method for determining relative permeability based on diffusion can include the following steps:

[0063] Step 101: Determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in the target core in saturated oil porous media;

[0064] Step 102: Determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas.

[0065] Step 103: Calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous media.

[0066] Step 104: Obtain the oil content in the target core considering diffusion effects;

[0067] Step 105: Determine the relative permeability of the oil phase and the relative permeability of the gas phase in the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil content considering diffusion.

[0068] In the example above, the diffusion effect of CO2 gas between crude oil particles is considered to determine the diffusion coefficient, oil yield, and oil content. Then, based on these parameters determined by considering the diffusion effect of CO2 gas between crude oil particles, the relative permeability of the oil phase and the relative permeability of the gas phase in the target core are determined. Because the diffusion effect of CO2 gas between crude oil particles is considered in the determination process, the results are more accurate. This method solves the technical problems of high accuracy and low efficiency in existing relative permeability calculations, achieving the technical effect of accurately and efficiently determining relative permeability.

[0069] Specifically, in implementation, the relative permeability of the oil phase and the relative permeability of the gas phase can be calculated using the following formula:

[0070]

[0071] Among them, K ro f represents the relative permeability of the oil phase. o (S g () indicates the oil content taking diffusion into account. This represents the dimensionless cumulative oil and gas production considering diffusion effects, where I represents the flow capacity ratio, and K... rg The gas phase relative permeability, m g Indicates gas phase viscosity, m o D represents the viscosity of the oil phase, and D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium. eThe coefficient representing the gas diffusion effect.

[0072] The effective diffusion coefficient of CO2 gas in saturated oil porous media can be obtained in the following manner, which may include the following steps:

[0073] S1: Cleaning, drying, and weighing the target core;

[0074] S2: Place the target core into an intermediate container filled with crude oil, and then pressurize it to the specified pressure to saturate the core;

[0075] S3: Use epoxy resin to seal the upper and lower end faces of the core to ensure that diffusion only exists in the radial direction;

[0076] S4: Connect the instruments and pipelines according to the experimental setup diagram, and check the airtightness of the experimental setup.

[0077] S5: Turn on the heating device and heat the experimental apparatus to the predetermined pressure;

[0078] S6: Open the valve connecting the intermediate container containing CO2 and the diffusion chamber. When the system pressure is relatively stable, close the valve connecting the intermediate container to CO2 and record the pressure decay data in the diffusion chamber during the experiment.

[0079] S7: When the pressure inside the diffusion chamber tends to stabilize, the experiment ends. Then, the effective diffusion coefficient of CO2 gas in saturated oil porous media can be calculated according to the following formula:

[0080]

[0081] in,

[0082] Where D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and K p V represents the slope of the fitted pressure drop curve. d r represents the gas volume excluding the core volume. o Z represents the radius of the target core, Z represents the gas compressibility coefficient, R represents the universal gas constant, T represents the temperature, and N represents the temperature. ￥ Dp represents the maximum mass of gas that can diffuse into the core. pg Z1 represents the pressure drop at time t, where t represents the diffusion time, p1 represents the initial pressure, p2 represents the equilibrium pressure, Z1 represents the compressibility factor of CO2 at pressure p1, Z2 represents the compressibility factor of CO2 at pressure p2, and V represents the gas volume.

[0083] Specifically, the isothermal compressibility of CO2 gas can be calculated using the following formula:

[0084]

[0085] Among them, C g The value represents the isothermal compressibility of CO2 gas, and P represents pressure.

[0086] Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas mentioned above, the coefficient representing the gas diffusion effect can be calculated according to the following formula:

[0087]

[0088] Among them, D e The coefficient representing gas diffusion, C g The isothermal compressibility of CO2 gas, m g S represents the gas phase viscosity, D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium, and S represents the gas phase viscosity. g The value represents the gas saturation, and K represents the permeability.

[0089] Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the diffusion band length can be calculated using the following formula:

[0090]

[0091] Where X represents the diffusion zone length, D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and t represents the diffusion time;

[0092] Then, based on the length of the diffusion zone, combined with the cross-sectional area and porosity of the core, the volume of the diffusion zone is calculated using the following formula:

[0093] V d =A×X×f

[0094] Among them, V d The diffuse zone volume is represented by A, the cross-sectional area of ​​the core is represented by f, and the porosity is represented by f.

[0095] Furthermore, based on the diffusion zone volume and the dimensionless cumulative oil production, the dimensionless cumulative oil production considering diffusion is calculated using the following formula:

[0096]

[0097] in, This represents the dimensionless cumulative oil production considering diffusion effects. This indicates the dimensionless cumulative oil production.

[0098] Right now, This represents the dimensionless cumulative oil production that takes into account diffusion effects. This represents the dimensionless cumulative production of oil and gas, taking into account diffusion effects. It only refers to oil. It is worth noting the total amount of oil and gas, all of which can be obtained through experimental measurement.

[0099] In implementation, an unsteady-state CO2-crude oil relative permeability test can be used to obtain conventional parameters such as oil production, gas production, and viscosity. Specifically, the following steps can be included:

[0100] S1: Clean and weigh the core, and at the same time, measure the length and diameter of the core;

[0101] S2: Place the core into the intermediate container and pressurize it to saturation. After saturation, weigh the core.

[0102] S3: Place the core after saturation with n-hexane into the core holder, evacuate the plugs and pipelines at both ends, and begin displacement after evacuation and preheating for 6 hours. During the displacement process, accurately record the cumulative time of oil breakthrough, as well as the cumulative time, cumulative gas production and cumulative oil production at each moment after oil and gas breakthrough.

[0103] S4: When the crude oil is displaced by CO2 to the residual oil state, the experiment ends. Then, the core is taken out and weighed to calculate the residual oil saturation.

[0104] The above method will be described below with reference to a specific embodiment. However, it is worth noting that this specific embodiment is only for better illustration of this application and does not constitute an improper limitation of this application.

[0105] Existing unsteady-state methods are inaccurate, primarily because they neglect the interaction between underground CO2 and crude oil, particularly the diffusion between CO2 and crude oil, leading to errors in the description of actual reservoir seepage processes. Therefore, the role of diffusion in accurately describing underground CO2-crude oil seepage needs to be considered in the calculation of relative permeability using unsteady-state methods. Based on this, this paper presents a calculation method that considers oil and gas diffusion in the determination of CO2-crude oil relative permeability using unsteady-state methods, aiming to accurately describe the reservoir seepage process and provide a more precise reference and guidance for CO2-assisted oil recovery.

[0106] Specifically, this example provides a method for testing the relative permeability of a CO2-crude oil system that takes into account diffusion, including the following steps 1 to 8:

[0107] Step 1: Calculate the diffusion coefficient of CO2 in saturated oil cores using the pressure drop method.

[0108] Step 2: Calculate the oil phase permeability based on the displacement experiment and Darcy's law, and use it as the benchmark value for the relative permeability of CO2-crude oil.

[0109] Specifically, a rock sample saturated with crude oil can be loaded into a core holder, and the crude oil can be passed through the rock sample under the action of a displacement pump at a certain pressure or flow rate. After the pressure difference between the inlet and outlet of the displacement rock sample and the outlet flow rate stabilize, the oil phase permeability can be calculated as the basic value of the oil-gas relative permeability.

[0110] Step 3: Calculate the isothermal compressibility of CO2 gas;

[0111] Specifically, the isothermal compressibility of a gas can be calculated using the following formula:

[0112]

[0113] Among them, C g P represents the isothermal compressibility of a gas, and P represents pressure, with the unit being Pa.

[0114] Step 4: Conduct an unsteady-state method to determine the relative permeability of CO2-crude oil, and obtain data such as oil production and gas production.

[0115] Step 5: Calculate the coefficient representing the diffusion effect of CO2 gas;

[0116] Specifically, the coefficient representing gas diffusion can be calculated using the following formula:

[0117]

[0118] Among them, D e The coefficient representing gas diffusion, in cm 2 / s;C g The isothermal compressibility of a gas is expressed in m. g D represents the gas phase viscosity, in mPa·s; D represents the diffusion coefficient of CO2 gas in saturated oil cores, in cm⁻¹. 2 / s;S g Indicates gas saturation, %; K represents permeability, 10. -3 μm 2 .

[0119] Step 6: Calculate the dimensionless cumulative oil production considering diffusion effects;

[0120] Specifically, the dimensionless cumulative oil production, taking into account diffusion, can be calculated using the following formula:

[0121]

[0122] V d =A×X×f

[0123]

[0124] Where X represents the length of the diffusion zone, in cm; and A represents the cross-sectional area of ​​the core, in cm². 2 ; t represents diffusion time, s; f represents porosity, %; V d Represents the volume of the diffusion zone, expressed as a multiple of the pore volume, as a decimal; This represents the dimensionless cumulative oil production, expressed as a multiple of pore volume, in decimal form. This represents the dimensionless cumulative oil production after considering CO2 diffused into the oil equivalent, expressed as a multiple of pore volume, in decimal form.

[0125] Step 7: Calculate the oil content and relative injection capacity of the gas phase, taking into account diffusion effects;

[0126] Specifically, the oil content and relative injection capacity of the gas phase, taking into account diffusion, can be determined using the following formula:

[0127]

[0128] Among them, f o (S g I(t) represents the oil content considering diffusion, a decimal; I(t) represents the relative injection capacity, also known as the flow capacity ratio, a constant. This represents the dimensionless cumulative production of oil and gas after considering CO2 diffused into the oil equivalent, expressed as a multiple of pore volume, in decimal form. This represents the dimensionless cumulative oil production, expressed as a multiple of pore volume, in decimal form. The total amount of dimensionless cumulative oil and gas produced is expressed as a multiple of pore volume, in decimal form; Q(t) represents the total amount of oil and gas produced at the core outlet at time t, in cm³. 3 / s; Q0 represents the total oil production at the core outlet at the initial moment, cm 3 / s; Dp0 represents the initial displacement pressure difference, MPa; Dp(t) represents the displacement pressure difference at time t, MPa.

[0129] Step 8: Calculate the relative permeability of the oil phase and the relative permeability of the gas phase, taking into account diffusion.

[0130] Specifically, the relative permeability of the oil phase and the relative permeability of the gas phase can be calculated using the following formula:

[0131]

[0132] Among them, S ge This indicates the gas saturation at the core outlet after considering diffusion, in %; m g The viscosity of the gas phase is expressed in mPa·s; m o Indicates oil phase viscosity, mPa·s; Kro K represents the relative permeability of the oil phase, a decimal. rg This represents the relative permeability of the gas phase, as a decimal.

[0133] This method addresses the shortcomings of traditional algorithms that do not consider the diffusion effect between CO2 and crude oil in processing CO2-crude oil relative permeability experimental data, thereby improving the accuracy of the measured CO2-crude oil relative permeability curve.

[0134] like Figure 2 The diagram shown is a structural diagram of the pressure drop method measuring device, including: CO2 cylinder 1, gas pressurization device 2, pressure monitoring system 5, temperature control system 6, CO2 intermediate container 7, core diffusion chamber 8, constant speed and constant pressure pumps 11 and 12, and control valves 3, 4, 9 and 10. Based on Figure 2 The experimental setup shown determines the diffusion coefficient of CO2 gas in saturated n-hexane crude oil cores using the pressure drop method. Specifically, it may include:

[0135] S1: The core is cleaned, dried, and weighed;

[0136] S2: Place the core into an intermediate container filled with crude oil and pressurize it to the specified pressure to saturate the core;

[0137] S3: Seal the upper and lower ends of the core with epoxy resin to ensure that diffusion exists only in the radial direction;

[0138] S4: According to Figure 2 Connect the instruments and pipelines shown in the experimental setup diagram, and check the airtightness of the experimental setup.

[0139] S5: Turn on the temperature control system 6 to heat the experimental apparatus to the predetermined pressure;

[0140] S6: Open control valves 3 and 4 to connect the valve between the intermediate container 7 containing CO2 and the diffusion chamber 8. When the system pressure is relatively stable, close control valves 3 and 4 and record the pressure decay data in the intermediate container 8 during the experiment.

[0141] S7: When the pressure inside the intermediate container 7 tends to stabilize, the experiment ends. The diffusion coefficient can be calculated using the following formula:

[0142]

[0143] in,

[0144] Where D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and K p V represents the slope of the fitted pressure drop curve. d r represents the gas volume excluding the core volume. oZ represents the radius of the target core, Z represents the gas compressibility coefficient, R represents the universal gas constant, T represents the temperature, and N represents the temperature. ￥ Dp represents the maximum mass of gas that can diffuse into the core. pg Z1 represents the pressure drop at time t, where t represents the diffusion time, p1 represents the initial pressure, p2 represents the equilibrium pressure, Z1 represents the compressibility factor of CO2 at pressure p1, Z2 represents the compressibility factor of CO2 at pressure p2, and V represents the gas volume.

[0145] Specifically, from the perspective of molecular motion and diffusion-dissolution, the pressure drop mainly stems from the random thermal motion and diffusion effect of gas molecules. When high and low pressure regions are connected, the concentration of gas molecules in the high-pressure region is higher, and the collision frequency is greater. Intermolecular interactions drive some gas molecules to diffuse into the low-pressure region. As diffusion continues, gas molecules in the high-pressure region gradually migrate, reducing their local molecular number density and thus causing a pressure drop. Furthermore, during diffusion, some gas molecules may dissolve in the liquid medium, further accelerating the pressure drop. This phenomenon reflects the molecular diffusion mechanism and its inherent regulation by equilibrium driving forces, providing experimental evidence for the determination of the diffusion coefficient. The pressure drop curve during the diffusion coefficient determination process is shown in the figure below. Figure 3 As shown in the figure, in the pressure drop curve, p1 represents the initial pressure and p2 represents the equilibrium pressure.

[0146] Specifically, in step 2 above, when calculating the oil phase permeability based on the displacement experiment and Darcy's law, and using it as the baseline value for the CO2-crude oil relative permeability, a core sample saturated with crude oil can be loaded into a core holder. The crude oil is then passed through the sample under the action of a displacement pump at a certain pressure or flow rate. After the pressure difference between the inlet and outlet of the displaced sample and the outlet flow rate stabilize, the oil phase permeability is measured three times consecutively. The relative deviation of this measurement is less than 3%, and this value is used as the baseline value for the oil-gas relative permeability. This is because the baseline value of permeability (i.e., the average of three permeability measurements) is not directly used when calculating the relative permeability of oil and gas using the unsteady-state method, as the calculation of relative permeability in the unsteady-state method mainly relies on experimental data such as fluid saturation, pressure gradient, and yield ratio. However, the baseline value of permeability still plays an important role in verifying the rationality of data and normalizing the relative permeability at endpoints. It can be used to check the accuracy of experimental results and describe the basic physical properties of the core. Therefore, measuring the baseline value of permeability is mainly to improve the stability and reliability of experimental data and to describe the properties of the core, rather than for direct calculation of relative permeability.

[0147] like Figure 4The diagram shows a schematic of an apparatus for determining the relative permeability of CO2-crude oil using a non-steady-state method. The apparatus includes: an intermediate container 1 containing crude oil, an intermediate CO2 container 2, constant-speed and constant-pressure pumps 3 and 9, control valves 4, 5, and 6, a two-way valve 7, a pressure monitoring system 8, a core holder 10, a back pressure valve 11, a liquid metering device 12, and a gas metering system 13. In step 4, [the process can be...] Figure 4 An unsteady-state CO2-crude oil relative permeability test was conducted to obtain conventional parameters such as oil production, gas production, and viscosity. Specifically, these parameters may include:

[0148] S1: Clean and weigh the target core, and measure the length and diameter of the target core at the same time;

[0149] S2: Place the core into the intermediate container and pressurize it to saturation. After saturation, weigh the core.

[0150] S3: Place the core after it is saturated with n-hexane into the core holder 10, evacuate the plugs and pipelines at both ends, and start displacement after evacuation and preheating for 6 hours; accurately record the cumulative time of oil breakthrough, as well as the cumulative time, cumulative gas production and cumulative oil production at each time after oil and gas breakthrough.

[0151] S4: When the crude oil is displaced by CO2 to the residual oil state, the experiment ends, the core is removed and weighed to calculate the residual oil saturation.

[0152] Specifically, in step 5 above, the oil phase flow velocity and gas phase flow velocity can be calculated according to Darcy's law using the following formula.

[0153]

[0154] Among them, v o Indicates the oil phase flow velocity, cm / s; v d This indicates the gas phase seepage velocity, in cm / s.

[0155] Furthermore, based on Fick's law and the equation of state, the gas-phase diffusion rate can be obtained by combining them:

[0156]

[0157] Among them, v f This represents the molecular diffusion rate, expressed in cm / s.

[0158] Calculate the flow fraction equation considering diffusion:

[0159]

[0160] For ease of calculation, let

[0161]

[0162] Among them, D e The coefficient representing gas diffusion, in cm 2 / s;C g The isothermal compressibility of a gas is expressed in m. g D represents the gas phase viscosity, in mPa·s; D represents the diffusion coefficient of CO2 gas in saturated oil cores, in cm⁻¹. 2 / s;S g Indicates gas saturation, %; K represents permeability, 10. -3 μm 2 , where v g Q represents the gas phase flow velocity considering diffusion, in cm / s; g Q represents gas flow rate, cm³ / s; o This indicates the oil phase flow rate, in cm³ / s.

[0163] Step 6 above may specifically include:

[0164] S1: Using the analytical solution of Fick's law, the diffusion distances at CO2 concentrations of 1% and 99% are obtained:

[0165] The formula for the analytical solution of concentration can be obtained from Fick's law as follows:

[0166]

[0167] For position x1 with a CO2 concentration of 1%, we have Solve for x1 by taking the logarithm.

[0168] For the position where CO2 concentration is 99% x2, we have Solve for x2 by taking the logarithm.

[0169] S2: Calculate and simplify the diffusion band length:

[0170] If we approximate the distance between locations with CO2 concentrations of 1% to 99% as the length of the diffusion band, then:

[0171]

[0172] Simplifying, we get:

[0173]

[0174] S3: Calculate the diffusion band volume:

[0175] V d =A×X×f

[0176] Where X represents the length of the diffusion zone, in cm; and A represents the cross-sectional area of ​​the core, in cm². 2 ; t represents diffusion time, s; f represents porosity, %; Vd Represents the volume of the diffusion zone, expressed as a multiple of the pore volume, as a decimal; This represents the dimensionless cumulative oil production, expressed as a multiple of pore volume, in decimal form. This represents the dimensionless cumulative oil production after considering CO2 diffused into the oil equivalent, expressed as a multiple of pore volume, in decimal form.

[0177] In step 8 above, the formula for calculating the relative permeability of the oil phase can be obtained. Combined with the flow fraction equation considering diffusion, a method for testing the relative permeability of CO2 considering diffusion can be derived, as shown below. Figure 5 The calculation results are shown in the figure.

[0178] The method described above can be applied to determine relevant parameters in CO2 and n-hexane crude oil displacement experiments using unsteady-state methods. These parameters can be substituted into an improved relative permeability correction formula that considers diffusion to obtain a corrected CO2-crude oil relative permeability curve. This method overcomes the problem of the existing JBN method neglecting the diffusion effect between CO2 and crude oil when calculating the CO2-crude oil relative permeability curve. The improved method in this example, which considers diffusion, provides a more accurate CO2-crude oil system relative permeability curve, better describing the characteristics of underground CO2-crude oil seepage.

[0179] The methods and embodiments provided in the above-described embodiments of this application can be executed in a mobile terminal, computer terminal, or similar computing device. Taking operation on an electronic device as an example... Figure 6 This is a hardware structure block diagram of an electronic device for a method of determining relative penetration rate provided in this application. (Example) Figure 6 As shown, the electronic device 610 may include one or more (only one is shown in the figure) processors 602 (processors 602 may include, but are not limited to, processing devices such as microprocessors (MCUs) or programmable logic devices (FPGAs), a memory 604 for storing data, and a transmission module 606 for communication functions. Those skilled in the art will understand that... Figure 6 The structure shown is for illustrative purposes only and does not limit the structure of the electronic device described above. For example, electronic device 610 may also include... Figure 6 The more or fewer components shown, or having the same Figure 6 The different configurations shown.

[0180] The memory 604 can be used to store software programs and modules of application software, such as the program instructions / modules corresponding to the method for determining the relative penetration rate in the embodiments of this application. The processor 602 executes various functional applications and data processing by running the software programs and modules stored in the memory 604, thereby realizing the method for determining the relative penetration rate of the application described above. The memory 604 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 604 may further include memory remotely located relative to the processor 602, and these remote memories can be connected to the electronic device 610 via a network. Examples of the above-mentioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0181] The transmission module 606 is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by the communication provider of the electronic device 610. In one example, the transmission module 606 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission module 606 may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0182] At the software level, the aforementioned device for determining relative permeability based on diffusion can be as follows: Figure 7 As shown, it includes:

[0183] The first determining module 701 is used to determine the effective diffusion coefficient of CO2 gas in the saturated oil porous medium and the isothermal compressibility of CO2 gas in the target core.

[0184] The second determining module 702 is used to determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas.

[0185] Calculation module 703 is used to calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium.

[0186] The acquisition module 704 is used to acquire the oil content in the target core considering diffusion.

[0187] The third determining module 705 is used to determine the relative permeability of the oil phase and the relative permeability of the gas phase of the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing the gas diffusion effect, the dimensionless cumulative oil production considering the diffusion effect, and the oil content considering the diffusion effect.

[0188] In one embodiment, the third determining module 705 can specifically calculate the relative permeability of the oil phase and the relative permeability of the gas phase according to the following formula:

[0189]

[0190] Among them, K ro f represents the relative permeability of the oil phase. o (S g () indicates the oil content taking diffusion into account. This represents the dimensionless cumulative oil and gas production considering diffusion effects, where I represents the flow capacity ratio, and K... rg The gas phase relative permeability, m g Indicates gas phase viscosity, m o D represents the viscosity of the oil phase, and D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium. e The coefficient representing the gas diffusion effect.

[0191] In one embodiment, the first determining module 701 can specifically calculate the effective diffusion coefficient of CO2 gas in a saturated oil porous medium according to the following formula:

[0192]

[0193] in,

[0194] Where D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and K p V represents the slope of the fitted pressure drop curve. d r represents the gas volume excluding the core volume. o Z represents the radius of the target core, Z represents the gas compressibility coefficient, R represents the universal gas constant, T represents the temperature, and N represents the temperature. ￥ Dp represents the maximum mass of gas that can diffuse into the core. pg Z1 represents the pressure drop at time t, where t represents the diffusion time, p1 represents the initial pressure, p2 represents the equilibrium pressure, Z1 represents the compressibility factor of CO2 at pressure p1, Z2 represents the compressibility factor of CO2 at pressure p2, and V represents the gas volume.

[0195] In one embodiment, the first determining module 701 can specifically calculate the isothermal compressibility of CO2 gas according to the following formula:

[0196]

[0197] Among them, C g The value represents the isothermal compressibility of CO2 gas, and P represents pressure.

[0198] In one embodiment, the second determining module 702 can specifically calculate the coefficient representing the gas diffusion effect according to the following formula:

[0199]

[0200] Among them, D e The coefficient representing gas diffusion, C g The isothermal compressibility of CO2 gas, m g S represents the gas phase viscosity, D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium, and S represents the gas phase viscosity. g The value represents the gas saturation, and K represents the permeability.

[0201] In one implementation, the calculation module 703 can specifically calculate the diffusion band length according to the following formula:

[0202]

[0203] Where X represents the diffusion zone length, D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and t represents the diffusion time;

[0204] Based on the length of the diffusion zone, combined with the cross-sectional area and porosity of the core, the volume of the diffusion zone is calculated using the following formula:

[0205] V d =A×X×f

[0206] Among them, V d The diffuse zone volume is represented by A, the cross-sectional area of ​​the core is represented by f, and the porosity is represented by f.

[0207] Based on the diffusion zone volume and the dimensionless cumulative oil production, the dimensionless cumulative oil production considering diffusion is calculated using the following formula:

[0208]

[0209] in, This represents the dimensionless cumulative oil production considering diffusion effects. This indicates the dimensionless cumulative oil production.

[0210] This application also provides a specific implementation of an electronic device capable of implementing all steps of the method for determining relative permeability based on diffusion in the above embodiments. The electronic device specifically includes: a processor, a memory, a communication interface, and a bus; wherein the processor, memory, and communication interface communicate with each other via the bus; the processor is used to call a computer program in the memory, and when the processor executes the computer program, it implements all steps of the method for determining relative permeability based on diffusion in the above embodiments. For example, when the processor executes the computer program, it implements the following steps:

[0211] Step 1: Determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in the target core in saturated oil porous media;

[0212] Step 2: Determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas.

[0213] Step 3: Calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous media.

[0214] Step 4: Obtain the oil content in the target core considering diffusion effects;

[0215] Step 5: Determine the relative permeability of the oil phase and the relative permeability of the gas phase in the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil content considering diffusion.

[0216] Embodiments of this application also provide a computer-readable storage medium capable of implementing all steps of the method for determining relative permeability based on diffusion in the above embodiments. The computer-readable storage medium stores a computer program that, when executed by a processor, implements all steps of the method for determining relative permeability based on diffusion in the above embodiments. For example, when the processor executes the computer program, it implements the following steps:

[0217] Step 1: Determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in the target core in saturated oil porous media;

[0218] Step 2: Determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas.

[0219] Step 3: Calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous media.

[0220] Step 4: Obtain the oil content in the target core considering diffusion effects;

[0221] Step 5: Determine the relative permeability of the oil phase and the relative permeability of the gas phase in the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil content considering diffusion.

[0222] As described above, this application's embodiments consider the diffusion effect of CO2 gas between crude oils to determine the diffusion coefficient, oil yield, oil content, etc., and then use these parameters, which take into account the diffusion effect of CO2 gas between crude oils, to determine the relative permeability of the oil phase and the relative permeability of the gas phase in the target core. Because the diffusion effect of CO2 gas between crude oils is considered in the determination process, the results are more accurate. This solution solves the technical problems of high accuracy and low efficiency in existing relative permeability calculations, achieving the technical effect of accurately and efficiently determining relative permeability.

[0223] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, hardware + program embodiments are relatively simple in description because they are fundamentally similar to method embodiments; relevant parts can be referred to the descriptions in the method embodiments.

[0224] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0225] While this application provides the method operation steps as described in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-inventive labor. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only execution order. In actual device or client product execution, the methods shown in the embodiments or drawings can be executed sequentially or in parallel (e.g., in a parallel processor or multi-threaded processing environment).

[0226] While this specification provides method operation steps as described in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-inventive means. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only execution order. In actual device or end product execution, the methods shown in the embodiments or drawings may be executed sequentially or in parallel (e.g., in a parallel processor or multi-threaded processing environment, or even a distributed data processing environment). The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, product, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, product, or apparatus. Without further limitations, the presence of other identical or equivalent elements in the process, method, product, or apparatus that includes said elements is not excluded.

[0227] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing the embodiments of this specification, the functions of each module can be implemented in one or more software and / or hardware components, or a module that performs the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0228] Those skilled in the art will also know that, besides implementing the controller using purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the controller function as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers (PLCs), and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the devices within it used to implement various functions can also be considered structures within that hardware component. Alternatively, the devices used to implement various functions can be considered as both software modules implementing the method and structures within a hardware component.

[0229] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0230] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0231] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0232] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0233] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0234] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0235] Those skilled in the art will understand that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, the embodiments of this specification can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, the embodiments of this specification can take the form of computer program products implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0236] The embodiments described in this specification can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. The embodiments of this specification can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0237] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, system embodiments are basically similar to method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0238] The above description is merely an embodiment of the present specification and is not intended to limit the embodiments of the present specification. For those skilled in the art, various modifications and variations can be made to the embodiments of the present specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments of the present specification should be included within the scope of the claims of the embodiments of the present specification.

Claims

1. A method for determining relative permeability based on diffusion, characterized in that, The method includes: Determine the effective diffusion coefficient and isothermal compressibility of CO2 gas in the target core in saturated oil porous media; The coefficient representing the gas diffusion effect is determined based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas. Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the dimensionless cumulative oil production considering diffusion is calculated. Obtain the oil content in the target core considering diffusion effects; Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil content considering diffusion, the relative permeability of the oil phase and the relative permeability of the gas phase in the target core are determined.

2. The method according to claim 1, characterized in that, Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing gas diffusion, the dimensionless cumulative oil production considering diffusion, and the oil cut considering diffusion, the relative permeability of the oil phase and the relative permeability of the gas phase in the target core are determined, including: The relative permeability of the oil phase and the relative permeability of the gas phase are calculated using the following formula: Among them, K ro f represents the relative permeability of the oil phase. o (S g () indicates the oil content taking diffusion into account. This represents the dimensionless cumulative oil and gas production considering diffusion effects, where I represents the flow capacity ratio, and K... rg The gas phase relative permeability, m g Indicates gas phase viscosity, m o D represents the viscosity of the oil phase, and D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium. e The coefficient representing the gas diffusion effect.

3. The method according to claim 1, characterized in that, Determine the effective diffusion coefficient of CO2 gas in the target core in saturated oil porous media, including: The effective diffusion coefficient of CO2 gas in saturated oil porous media is calculated using the following formula: in, Where D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and K p V represents the slope of the fitted pressure drop curve. d r represents the gas volume excluding the core volume. o Z represents the radius of the target core, Z represents the gas compressibility coefficient, R represents the universal gas constant, T represents the temperature, and N represents the temperature. ￥ Dp represents the maximum mass of gas that can diffuse into the core. pg Z1 represents the pressure drop at time t, where t represents the diffusion time, p1 represents the initial pressure, p2 represents the equilibrium pressure, Z1 represents the compressibility factor of CO2 at pressure p1, Z2 represents the compressibility factor of CO2 at pressure p2, and V represents the gas volume.

4. The method according to claim 1, characterized in that, Determining the isothermal compressibility of CO2 gas includes: The isothermal compressibility of CO2 gas is calculated using the following formula: Among them, C g The value represents the isothermal compressibility of CO2 gas, and P represents pressure.

5. The method according to claim 1, characterized in that, Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas, coefficients representing the gas diffusion effect are determined, including: Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media and the isothermal compressibility of CO2 gas, the coefficient representing the gas diffusion effect is calculated according to the following formula: Among them, D e The coefficient representing gas diffusion, C g The isothermal compressibility of CO2 gas, m g S represents the gas phase viscosity, D represents the effective diffusion coefficient of CO2 gas in a saturated oil porous medium, and S represents the gas phase viscosity. g The value represents the gas saturation, and K represents the permeability.

6. The method according to claim 1, characterized in that, Based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the dimensionless cumulative oil production considering diffusion effects is calculated, including: The diffusion band length is calculated using the following formula based on the effective diffusion coefficient of CO2 gas in saturated oil porous media: Where X represents the diffusion zone length, D represents the effective diffusion coefficient of CO2 gas in saturated oil porous media, and t represents the diffusion time; Based on the length of the diffusion zone, combined with the cross-sectional area and porosity of the core, the volume of the diffusion zone is calculated using the following formula: In d =A×X×f Among them, V d The diffuse zone volume is represented by A, the cross-sectional area of ​​the core is represented by f, and the porosity is represented by f. Based on the diffusion zone volume and the dimensionless cumulative oil production, the dimensionless cumulative oil production considering diffusion is calculated using the following formula: V o ￠(t)=V o (t)+V d Among them, V o ￠(t) represents the dimensionless cumulative oil production considering diffusion effects, V o (t) represents the dimensionless cumulative oil production.

7. A device for determining relative permeability based on diffusion, characterized in that, include: The first determining module is used to determine the effective diffusion coefficient of CO2 gas in the saturated oil porous medium and the isothermal compressibility of CO2 gas in the target core. The second determining module is used to determine the coefficient representing the gas diffusion effect based on the effective diffusion coefficient of CO2 gas in saturated oil porous medium and the isothermal compressibility of CO2 gas. The calculation module is used to calculate the dimensionless cumulative oil production considering diffusion based on the effective diffusion coefficient of CO2 gas in saturated oil porous media. The acquisition module is used to obtain the oil content in the target core considering diffusion effects; The third determination module is used to determine the relative permeability of the oil phase and the relative permeability of the gas phase of the target core based on the effective diffusion coefficient of CO2 gas in saturated oil porous media, the coefficient representing the gas diffusion effect, the dimensionless cumulative oil production considering the diffusion effect, and the oil content considering the diffusion effect.

8. An electronic device comprising a processor and a memory for storing processor-executable instructions, characterized in that, When the processor executes the instructions, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in any one of claims 1 to 6.

10. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method described in any one of claims 1 to 6.

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