Method and device for calculating productivity of carbon dioxide-water alternating gas drive in tight oil reservoirs

Abstract

The embodiment of the specification provides a method and device for calculating productivity of carbon dioxide-water alternating gas drive in tight oil reservoirs, which comprises establishing oil-gas-water three-phase continuity equations of matrix systems and artificial fracture systems respectively; establishing motion equations of the matrix systems and the artificial fracture systems respectively; establishing auxiliary equations including at least three-phase channeling equations, molecular diffusion equations and phase permeability equations; obtaining seepage differential equations of the matrix systems and the artificial fracture systems, initial conditions and internal and external boundary conditions thereof according to the continuity equations, the motion equations and the auxiliary equations; discretely processing the seepage differential equations of the matrix systems and the artificial fracture systems by using a finite difference method, and solving to obtain oil-gas-water three-phase three-dimensional difference equations of the matrix systems and the artificial fracture systems; and calculating injection-production productivity of the carbon dioxide-water alternating gas drive in the tight oil reservoirs according to the three-phase three-dimensional difference equations. The method can establish accurate seepage equations, and improve the accuracy of seepage law calculation and oilfield development effect evaluation.

Description

Technical Field

[0001] The embodiments in this specification relate to the field of oil and gas development technology, and in particular to a method and apparatus for calculating the production capacity of tight oil reservoirs using carbon dioxide-water-gas alternating flooding. Background Technology

[0002] Accurate prediction of reservoir production dynamics is a crucial foundation for evaluating oilfield development effectiveness and designing rational development plans. However, describing and predicting reservoir production dynamics requires a clear understanding of reservoir fluid seepage patterns. Tight reservoirs, with their small pore throat size and dense pores, are significantly affected by carbon dioxide diffusion and mass transfer, which is a major factor influencing the seepage patterns of carbon dioxide-water-gas alternating flow. In addition, factors such as carbon dioxide diffusion dissolution and viscosity reduction, diffusion mass transfer, capillary pressure, and relative permeability lag all influence the seepage patterns of carbon dioxide-water-gas alternating flow in tight reservoirs. Furthermore, the current practice of using artificial hydraulic fracturing to develop tight reservoirs also affects the seepage patterns due to the artificial fractures created. These multiple factors contribute to the complexity of the carbon dioxide-water-gas alternating flow mechanism in tight reservoirs, making accurate characterization difficult.

[0003] Current technologies do not consider the impact of molecular diffusion and mass transfer in water slugs formed during water-gas alternating flooding on the seepage patterns of carbon dioxide-water-gas alternating flooding in tight oil reservoirs, resulting in inaccurate characterization of seepage in this process. Furthermore, factors such as capillary pressure, gravity, fractures, and carbon dioxide channeling also influence the seepage patterns. Therefore, there is an urgent need to develop a comprehensive method for characterizing seepage in carbon dioxide-water-gas alternating flooding in tight oil reservoirs that considers numerous factors, including carbon dioxide diffusion and mass transfer, capillary pressure, gravity, fractures, and carbon dioxide channeling, to achieve accurate prediction and evaluation of production capacity. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the purpose of the embodiments in this specification is to provide a method and apparatus for calculating the production capacity of tight oil reservoirs by carbon dioxide-water-gas alternating flooding, thereby solving the problem in the prior art that it is difficult to accurately characterize the seepage flow of tight oil reservoirs by carbon dioxide-water-gas alternating flooding, which leads to inaccurate prediction and calculation of oil reservoir production capacity.

[0005] To solve the above-mentioned technical problems, the specific technical solutions of the embodiments in this specification are as follows:

[0006] In a first aspect, embodiments of this specification provide a method for calculating the productivity of a tight oil reservoir using a carbon dioxide-water-gas alternating flooding system, the method comprising:

[0007] Based on the law of conservation of mass, three-phase continuity equations for oil, gas, and water are established for both the matrix system and the artificial fracture system.

[0008] Considering the initiation pressure gradient, capillary pressure, and gravity, the equations of motion for the matrix system and the artificial fracture system are established respectively.

[0009] Establish auxiliary equations, which include at least the three-phase crossflow equation of oil, gas and water, the molecular diffusion equation of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase cross-permeability equation of oil, gas and water considering the lag of cross-permeability.

[0010] Based on the continuity equation, the motion equation, and the auxiliary equation, the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, are obtained respectively.

[0011] The seepage differential equations of the matrix system and the artificial fracture system were discretized using the finite difference method, and the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system were obtained by solving them.

[0012] Based on the three-dimensional difference equations of oil, gas, and water in the matrix system and artificial fracture system, the production capacity of the tight oil reservoir through alternating carbon dioxide-water-gas flooding is calculated.

[0013] Secondly, a device for calculating the productivity of tight oil reservoirs using carbon dioxide-water-gas alternating flooding, the device comprising:

[0014] The first module is used to establish the three-phase continuity equations of oil, gas, and water for the matrix system and the artificial fracture system, respectively, based on the law of conservation of mass.

[0015] The second module is used to establish the motion equations of the matrix system and the artificial fracture system, taking into account the initiation pressure gradient, capillary pressure and gravity factors.

[0016] The third module is used to establish auxiliary equations, which include at least the three-phase flow equations of oil, gas and water, the molecular diffusion equation of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase interpenetration equations of oil, gas and water considering the lag of interpenetration.

[0017] The solution module is used to obtain the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, based on the continuity equation, the motion equation and the auxiliary equation, respectively.

[0018] The discretization module is used to discretize the seepage differential equations of the matrix system and the artificial fracture system using the finite difference method, and solve them to obtain the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system.

[0019] The calculation module is used to calculate the production capacity of the tight oil reservoir by the three-dimensional difference equations of oil, gas and water phases of the matrix system and the artificial fracture system.

[0020] Thirdly, embodiments of this specification also provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method provided by the above-described technical solution.

[0021] Using the above technical solution, the embodiment of this specification provides a method and apparatus for calculating the production capacity of carbon dioxide-water-gas alternating flooding in tight oil reservoirs. It comprehensively considers factors such as crossflow between the matrix and fractures, starting pressure gradient, capillary pressure and gravity factors, as well as carbon dioxide molecule diffusion mass transfer. It realizes the accurate construction of the seepage equation for carbon dioxide-water-gas alternating flooding in tight oil reservoirs, improves the accuracy of seepage law calculation, and solves the three-dimensional difference equations of oil, gas and water in the matrix system and artificial fracture system. This is beneficial for accurately predicting reservoir production dynamics, improving the accuracy of oilfield development effect evaluation, and designing accurate and suitable development plans for oilfields.

[0022] To make the above and other objects, features and advantages of the embodiments of this specification more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This document illustrates a step-by-step diagram of a method for calculating the productivity of a tight oil reservoir using a carbon dioxide-water-gas alternating flooding system, as provided in an embodiment of this specification.

[0025] Figure 2 The diagram illustrates the steps for calculating the diffusion coefficient affected by water drive and the diffusion coefficient not affected by water drive in the embodiments of this specification.

[0026] Figure 3 A schematic diagram illustrating the steps for verifying the three-dimensional difference equations of oil, gas, and water in a matrix system and an artificial fracture system is shown.

[0027] Figure 4 A schematic diagram showing the comparison and verification between the cumulative oil production output data obtained using the Eclipse production well model and the cumulative oil production capacity data calculated using the three-dimensional difference equation of the oil, gas and water phases using the matrix system and artificial fracture system is shown.

[0028] Figure 5A schematic diagram showing the comparison and verification of gas-oil ratio output data obtained using the Eclipse production well model and gas-oil ratio production capacity data calculated using the three-dimensional difference equation of oil, gas and water phases using the matrix system and artificial fracture system is shown.

[0029] Figure 6 This specification shows a schematic diagram of a tight oil reservoir carbon dioxide-water-gas alternating flooding production capacity calculation device provided in an embodiment of the present specification;

[0030] Figure 7 A schematic diagram of the structure of a computer device provided in an embodiment of this specification is shown.

[0031] Explanation of symbols in the attached drawings:

[0032] 61. First module creation;

[0033] 62. Second module setup;

[0034] 63. The third module is established;

[0035] 64. Solver module;

[0036] 65. Discrete processing module;

[0037] 66. Calculation module;

[0038] 702. Computer equipment;

[0039] 704, Processor;

[0040] 706. Memory;

[0041] 708. Drive mechanism;

[0042] 710. Input / Output Module;

[0043] 712. Input devices;

[0044] 714. Output devices;

[0045] 716. Presentation equipment;

[0046] 718. Graphical User Interface;

[0047] 720. Network interface;

[0048] 722. Communication link;

[0049] 724. Communication bus. Detailed Implementation

[0050] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0051] It should be noted that the terms "first," "second," etc., used in this specification, claims, and the foregoing drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0052] This specification provides a method and apparatus for calculating the production capacity of carbon dioxide-water-gas alternating flooding in tight oil reservoirs. It can comprehensively consider the influence of factors such as molecular diffusion and mass transfer in water slugs formed by water-gas alternating flooding, capillary pressure, gravity, fractures, and carbon dioxide channeling on the seepage law, thereby improving the accuracy of seepage characterization in carbon dioxide-water-gas alternating flooding of tight oil reservoirs and thus improving the accuracy of production capacity prediction. Figure 1 This diagram illustrates the steps of a method for calculating the productivity of a tight oil reservoir using a carbon dioxide-water-gas alternating flooding system, as provided in the embodiments of this specification. This specification provides the operational steps described in the embodiments or flowcharts, but based on conventional or non-inventive methods, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only possible execution order. In actual system or device products, the methods shown in the embodiments or drawings can be executed sequentially or in parallel. Specifically, as shown in the attached diagrams... Figure 1 As shown, the method may include:

[0053] S110: Based on the law of conservation of mass, establish the three-phase continuity equations for oil, gas, and water in the matrix system and the artificial fracture system, respectively.

[0054] Specifically, in the embodiments of this specification, the oil, gas, and water three-phase continuity equations of the matrix system and the artificial fracture system take into account the crossflow between the matrix system and the artificial fracture system. Therefore, the oil, gas, and water three-phase continuity equation of the matrix system is:

[0055]

[0056] In formula (1):

[0057]

[0058] Where ▽ is the Hamiltonian operator, ρ om For the oil phase density in the matrix system, 10 3 kg / m 3 ;υ om ω represents the oil phase flow velocity in the matrix system, in m / s. oim B represents the mass content (%) of oil phase i in the matrix system; om Let m be the volume factor of the oil phase in the matrix system. 3 / m 3 ;q oimf m represents the amount of oil phase i component exchanged between the artificial fracture system and the matrix system due to pressure differential. 3 / s;φ m Porosity of the matrix system, %; S om F represents the saturation of oil phase i component in the matrix system, in %; om The mass diffusion flux of carbon dioxide into the oil phase of the matrix system is expressed in kg / (m³). 2 ·s); a is the quantity of oil phase components;

[0059] ρ gm For the gas phase density in the matrix system, 10 3 kg / m 3 ;υ gm ω represents the vapor flow velocity in the matrix system, in m / s; gim B represents the mass content (%) of the gas phase i component in the matrix system. gm Let m be the volume factor of the gas phase in the matrix system. 3 / m 3 ;q gimf m represents the amount of exchange between the crack and the gas phase i component of the matrix system caused by the pressure difference. 3 / s;S gm denoted as i, the saturation degree of gas phase component i in the matrix system, in %; b represents the quantity of gas phase component i.

[0060] ρ wm The density of the aqueous phase in the matrix system is 10. 3 kg / m 3 ;υ wm B represents the aqueous phase flow velocity in the matrix system, in m / s; wm Water volume index in the matrix system, m 3 / m 3 ;q wmf Due to the pressure difference, the amount of water exchanged between the artificial fracture system and the matrix system, m3 / s;S wm The water saturation level in the matrix system is expressed as %.

[0061] The three-phase continuity equation for oil, gas, and water in an artificial fracture system is as follows:

[0062]

[0063] Where, ρ of The density of the oil phase in the artificial fracture system is 10. 3 kg / m 3 ;υ of ω represents the oil phase flow velocity in the artificial fracture system, in m / s; oif B represents the mass content (%) of oil phase i component in the artificial fracture system. of Let m be the oil phase volume factor in the artificial fracture system. 3 / m 3 ;q oi m represents the amount of oil phase i component artificially extracted in the flow unit. 3 / s;F of The mass diffusion flux of carbon dioxide into the oil phase of the artificial fracture system is expressed in kg / (m³). 2 ·s); φ f Porosity of the artificial fracture system, %; S of The saturation of oil phase i component in the artificial fracture system, in %;

[0064] ρ gf The gas phase density in the artificial fracture system is 10. 3 kg / m 3 ;υ gf ω represents the vapor flow velocity in the artificial fracture system, in m / s; gif B represents the mass content (%) of gas phase i component in the artificial fracture system. gf Let m be the volume factor of the gas phase in the artificial fracture system. 3 / m 3 ;q gi m represents the difference in artificial injection and production of gas phase i component in the flow unit. 3 / s;S gf Let represent the saturation level of gas phase i component in the artificial fracture system, in %;

[0065] ρ wf The density of the water phase in the artificial fracture system is 10. 3 kg / m 3 ;υ wf B represents the water phase seepage velocity in the artificial fracture system, in m / s; wf Let m be the water volume factor in the artificial fracture system. 3 / m 3 ;q wThe difference between water phase artificial injection and production in the flow unit, m 3 / s;S wf The water saturation level in the artificial fracture system is %.

[0066] S120: Considering the initiation pressure gradient, capillary pressure, and gravity, establish the motion equations for the matrix system and the artificial fracture system, respectively.

[0067] Specifically, the equation of motion takes into account the initiation pressure gradient, capillary pressure, and gravity, wherein the equation of motion for the matrix system is:

[0068]

[0069] Among them, υ om K represents the oil phase flow velocity in the matrix system, in m / s; m The absolute permeability of the matrix system, 10 -3 μm 2 ;K ro The relative permeability of the oil phase is dimensionless; μ om ρ is the oil phase viscosity in the matrix system, mPa·s; ▽ is the Hamiltonian operator, P om For the oil phase pressure of the matrix system, Pa; G o Oil phase start-up pressure gradient, MPa / m; ρ om For the oil phase density in the matrix system, 10 3 kg / m 3 g is the acceleration due to gravity, m / s² 2 H represents the height difference, in meters.

[0070] υ gm K represents the vapor flow velocity in the matrix system, in m / s. rg μ represents the relative permeability of the gas phase, which is dimensionless. gm P represents the gas phase viscosity in the matrix system, in mPa·s; gm G represents the gas phase pressure of the matrix system, in Pa; g The gas phase initiation pressure gradient is given in MPa / m; ρ gm For the gas phase density in the matrix system, 10 3 kg / m 3 ;

[0071] υ wm K represents the aqueous phase flow velocity in the matrix system, in m / s. rw The relative permeability of the aqueous phase is dimensionless; μ wm P represents the viscosity of the aqueous phase in the matrix system, in mPa·s. wm The aqueous phase pressure of the matrix system is Pa; G w The starting pressure gradient for the aqueous phase is MPa / m; ρ wmFor a matrix system with an aqueous phase density of 10 3 kg / m 3 .

[0072] The equation of motion for the artificial fracture system is:

[0073]

[0074] Among them, υ of K represents the oil phase flow velocity in the artificial fracture system, in m / s. f The absolute permeability of the artificial fracture system, 10 -3 μm 2 μ of The viscosity of the oil phase in the artificial fracture system is given in mPa·s; P of The oil phase pressure of the artificial fracture system is given in Pa; ρ of The density of the oil phase in the artificial fracture system is 10. 3 kg / m 3 ;

[0075] υ gf The vapor flow velocity in the artificial fracture system is expressed in m / s; μ gf The viscosity of the gas phase in the artificial fracture system is given in mPa·s; P0 gf The vapor pressure of the artificial fracture system is given in Pa; ρ gf The gas phase density in the artificial fracture system is 10. 3 kg / m 3 ;

[0076] υ wf The water phase seepage velocity in the artificial fracture system is expressed in m / s; μ wf The viscosity of the aqueous phase in the artificial fracture system is given in mPa·s; P wf The water phase pressure in the artificial fracture system is Pa; ρ wf The density of the water phase in the artificial fracture system, 10 3 kg / m 3 .

[0077] S130: Establish auxiliary equations, which include at least the three-phase flow equations of oil, gas and water, the molecular diffusion equations of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase interpenetration equations of oil, gas and water considering the hysteresis of interpenetration.

[0078] Due to the pressure difference between the matrix system and the artificial fracture system, oil, gas, and water cross-flow occurs between them. The cross-flow flow rate in the cross-flow equation is:

[0079]

[0080] Where, qoimf m represents the amount of oil phase exchanged between the artificial fracture system and the matrix system due to pressure differential. 3 / s; σ is the shape factor of the contact area between cracks and bedrock per unit volume of rock, ω oim K represents the mass content (%) of oil phase i component in the matrix system. m The absolute permeability of the matrix system, 10 -3 μm 2 ;K ro The relative permeability of the oil phase is dimensionless; μ o B is the viscosity of the oil phase, in mPa·s. om Let m be the volume factor of the oil phase in the matrix system. 3 / m 3 ;P om P represents the oil phase pressure in the matrix system, in Pa; of Here is the oil phase pressure in the artificial fracture system, in Pa;

[0081] q gimf m represents the amount of gas phase exchanged between the artificial fracture system and the matrix system due to pressure difference. 3 / s;ω gim K represents the mass content of gaseous component i in the matrix system, in %; rg μ represents the relative permeability of the gas phase, which is dimensionless. g B is the gas phase viscosity, mPa·s; gm Let m be the volume factor of the gas phase in the matrix system. 3 / m 3 ;P gm P represents the gas phase pressure in the matrix system, in Pa; gf Here is the gas phase pressure in the artificial fracture system, in Pa;

[0082] q wmf m represents the amount of water phase exchanged between the artificial fracture system and the matrix system due to pressure difference. 3 / s;K rw The relative permeability of the aqueous phase is dimensionless; μ w B is the viscosity of the aqueous phase, in mPa·s. wm Water volume index in the matrix system, m 3 / m 3， P wm P represents the pressure of the aqueous phase in the matrix system, in Pa; wf ρ is the water phase pressure in the artificial fracture system, in Pa.

[0083] And, the molecular diffusion equation is:

[0084]

[0085] Among them, F omThe mass diffusion flux of carbon dioxide in crude oil within the matrix system is expressed in kg / (m³). 2 ·s); F of The mass diffusion flux of carbon dioxide in crude oil in an artificial fracture system is expressed in kg / (m³). 2 ·s); M is the molar mass of carbon dioxide, kg / mol; C om C represents the molar concentration of carbon dioxide in the crude oil of the matrix system, in mol / L. of ∠ρ is the molar concentration of carbon dioxide in crude oil in an artificial fracture system, in mol / L; ∠∠ is the Hamiltonian operator; D is the carbon dioxide diffusion coefficient, in m. 2 / s.

[0086] The equation for the three-phase interpermeability of oil, gas, and water with sluggish interpermeability is as follows:

[0087]

[0088] Among them, K rw The relative permeability of the aqueous phase is dimensionless; a w S represents the endpoint value of the relative permeability of the water phase in an oil-water two-phase system; wi Water saturation, %; S orw K represents the residual oil saturation in the oil-water two-phase system, in %; row The relative permeability of the oil phase in an oil-water two-phase system is dimensionless; a ow This represents the endpoint value of the relative permeability of the oil phase in the oil-water two-phase system.

[0089] K rg The relative permeability of the gas phase is dimensionless; a g S represents the endpoint value of the relative permeability of the gas phase in the oil and gas two-phase system. gc Critical gas saturation, %; S org K represents the residual oil saturation in the oil and gas two-phase system, in %; rog The relative permeability of the oil phase in the two-phase oil-gas mixture is dimensionless; a og This represents the endpoint value of the relative permeability of the oil phase in the two-phase oil and gas system.

[0090] S140: Based on the continuity equation, the motion equation, and the auxiliary equation, the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, are obtained respectively.

[0091] Substitute equations (5) to (8) into equations (1) and (3) respectively to obtain the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions.

[0092] S150: The seepage differential equations of the matrix system and the artificial fracture system are discretized using the finite difference method, and the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system are obtained by solving them.

[0093] S160: Calculate the production capacity of the tight oil reservoir based on the three-dimensional difference equations of the oil, gas, and water phases of the matrix system and the artificial fracture system.

[0094] This specification provides a method for calculating the production capacity of tight oil reservoirs using carbon dioxide-water-gas alternating flooding. By constructing a three-phase continuity equation for the matrix system and the artificial fracture system, considering crossflow between the matrix and fractures, and by constructing motion equations considering the starting pressure gradient, capillary pressure, and gravity, as well as auxiliary equations for crossflow caused by the pressure difference between the matrix system and the artificial system, and auxiliary equations for carbon dioxide molecular diffusion, the method achieves accurate construction of the seepage equation for tight oil reservoirs using carbon dioxide-water-gas alternating flooding. This improves the accuracy of seepage law calculations and allows for the solution of three-dimensional difference equations for the oil, gas, and water phases of the matrix system and the artificial fracture system. This facilitates accurate prediction of reservoir production dynamics, improves the accuracy of oilfield development effect evaluation, and enables the design of accurate and suitable development plans for the oilfield.

[0095] In formula (6), the shape factor σ is calculated using the following formula:

[0096]

[0097] Among them, l x Let l be the length of the matrix system in the x-direction, in meters (m); y Let l be the length of the matrix system in the y-direction, in meters (m); z Let be the length of the matrix system in the z-direction, in meters.

[0098] Then formula (6) can be transformed into:

[0099]

[0100] In the formula: l is the flow distance between the matrix and the crack (in meters), and we have:

[0101]

[0102] Furthermore, the auxiliary equation also includes the capillary pressure equation:

[0103] P cog =P g -P o (12)

[0104] P cow =P o -P w (13)

[0105] Among them, P cog P represents the capillary pressure of the oil-gas two-phase system, in Pa. gP is the capillary pressure in the gas phase, in Pa. o P is the capillary pressure of the oil phase, in Pa; cow P represents the capillary pressure of the oil-water two-phase system, in Pa. w The pressure is the capillary pressure in the aqueous phase, in Pa.

[0106] The auxiliary equations also include a molar content constraint equation and a saturation constraint equation, wherein the molar content constraint equation is:

[0107]

[0108] Where, ω oi ω represents the molar content of component i in the oil phase; gi Z represents the molar content of component i in the gas phase. i Let i be the molar content of component i in the oil and gas phases, in %; that is, to normalize the mass content of each component in the oil and gas and the molar content of each phase, ensuring that the sum is 1.

[0109] The saturation constraint equation is:

[0110] S o +S g +S w =1 (15)

[0111] Among them, S o Oil saturation, %; S g For gas saturation, %; and for S w The percentage is the water saturation level.

[0112] Furthermore, in the molecular diffusion equation (Formula 7) constructed in step S130, the carbon dioxide diffusion coefficient includes the diffusion coefficient of carbon dioxide when diffusing in a reservoir affected by water drive and the diffusion coefficient when diffusing in a reservoir not affected by water drive, such as... Figure 2 As shown, the diffusion coefficients of carbon dioxide in reservoirs affected by waterflooding and in reservoirs not affected by waterflooding are calculated through the following steps:

[0113] S210: The reservoir is treated with saturated water and saturated oil to make at least part of the reservoir unaffected by water drive and to make at least part of the reservoir affected by water drive.

[0114] S220: A supercritical carbon dioxide diffusion test is conducted on the reservoir from the water-driven reservoir to the un-water-driven reservoir.

[0115] S230: Construct a one-stage diffusion model of carbon dioxide in reservoirs affected by water drive and a two-stage diffusion model in reservoirs not affected by water drive.

[0116] The one-stage diffusion model is as follows:

[0117] C(x,t)=C i1 +f(x,t) (16)

[0118]

[0119] Where C(x,t) is the concentration of carbon dioxide at position x in the reservoir at time t, C i1 The concentration of carbon dioxide at the initial moment of diffusion in a water-driven reservoir, in mol / m³. 3 f(x,t) is the introduced carbon dioxide deviation factor correction function; D e1 Let m be the diffusion coefficient of carbon dioxide during diffusion in a water-driven reservoir. 2 / s; τ is tortuosity, φ is porosity, %;

[0120] The initial conditions for the one-stage diffusion model are:

[0121] f(x,t)=-C i1 (t=0,0<x<L) (18)

[0122] Its boundary conditions are:

[0123] f(x,t)=0(x=0,0<t<t1) (19)

[0124]

[0125] Where L is the reservoir length in meters (m), and t1 is the time it takes for carbon dioxide to diffuse to the interface between the water-driven reservoir and the un-water-driven reservoir, in seconds (s).

[0126] The two-stage diffusion model is as follows:

[0127]

[0128] Among them, D e2 Let m be the diffusion coefficient of carbon dioxide in a reservoir unaffected by water drive. 2 / s; In the embodiments of this specification, the lengths of the reservoirs affected by waterflooding and those not affected by waterflooding are equal, i.e., both are... t2 is the time it takes for carbon dioxide to diffuse completely in a reservoir unaffected by water flooding, measured in seconds.

[0129] The initial conditions for the two-stage diffusion model are:

[0130]

[0131] The boundary conditions for the two-stage diffusion model are:

[0132] C(x,t)=Ci2 (x=0,t>0) (23)

[0133]

[0134] Among them, C i2 Let be the initial concentration of carbon dioxide during diffusion in a reservoir unaffected by water drive, in mol / m³. 3 .

[0135] S240: Solve the first-stage diffusion model to obtain the diffusion coefficient of carbon dioxide when it diffuses in a reservoir affected by water drive, and solve the second-stage diffusion model to obtain the diffusion coefficient of carbon dioxide when it diffuses in a reservoir not affected by water drive.

[0136] Using the method of separation of variables, the one-stage diffusion model was solved, yielding the following results:

[0137]

[0138] During the diffusion of carbon dioxide in a water-driven reservoir, the change in the molar amount of carbon dioxide is as follows:

[0139]

[0140] Where, ΔM I The molar amount of carbon dioxide diffusing into crude oil in a water-driven reservoir (in mol).

[0141] The change in the molar volume of carbon dioxide during diffusion in a reservoir unaffected by water drive is as follows:

[0142]

[0143] Where, ΔM II The molar amount of carbon dioxide diffusing into crude oil in a reservoir not affected by water drive (in mol).

[0144] By solving formulas (25) and (27), the diffusion coefficients of carbon dioxide in reservoirs affected by water drive and reservoirs not affected by water drive can be obtained respectively. These coefficients can then be substituted into the molecular diffusion equation, i.e., formula (7). Thus, the tight oil reservoir carbon dioxide-water-gas alternating drive production capacity calculation provided in the embodiments of this specification further considers the influence of carbon dioxide-water-gas alternating drive on carbon dioxide diffusion and mass transfer, thereby making the constructed tight oil reservoir carbon dioxide-water-gas alternating drive seepage equation more accurate, thereby improving the accuracy of the calculation of the three-dimensional difference equations of oil, gas and water in the matrix system and artificial fracture system.

[0145] Therefore, the seepage differential equation of the matrix system obtained in step S140 is:

[0146]

[0147] Furthermore, the seepage differential equation for the artificial fracture system is:

[0148]

[0149] Furthermore, the initial conditions are:

[0150]

[0151] Where P is the formation pressure, in Pa; P i The original formation pressure is Pa; ω oi ω represents the molar content of component i in the oil phase; gi x represents the molar content of component i in the gas phase; oi y represents the molar content of oil phase component i at the initial moment; gi The initial molar content of gas phase component i is given.

[0152] The outer boundary conditions are:

[0153] Assuming the reservoir boundary is a closed boundary and an impermeable boundary, then there is no flow at the boundary, i.e.:

[0154]

[0155] The inner boundary conditions are:

[0156] At coordinates (0, 0) and (l) x , l y At point ), there is a production well or injection well. If the production well is producing at constant pressure, then:

[0157] P prwf =P1 (32)

[0158] Injection well pressure control, i.e.:

[0159] P inwf =P2 (33)

[0160] Among them, P prwf The production well pressure is given in Pa; P inwf The injection well pressure is expressed in Pa.

[0161] By discretizing the oil phase seepage equation in formula (28) using the finite difference method, taking the conductivity coefficient, capillary force, gravity, and molecular diffusion as explicit and the pressure as implicit, we can obtain:

[0162] The three-dimensional difference equations for the oil, gas, and water phases of the matrix system are as follows:

[0163]

[0164] in,

[0165]

[0166]

[0167] V ijk =Δx i Δy j Δz k (37)

[0168]

[0169]

[0170]

[0171] Where Δ is the change. P represents the differential introduction amount of component i in the oil phase of the matrix system at time step n. n+1 The pressure at time step n+1, in Pa; Let be the oil phase density of the matrix system at time step n, 10 3 kg / m 3 g is the acceleration due to gravity, m / s² 2 H represents the height difference, in meters. Let n be the mass diffusion flux of carbon dioxide into the oil phase of the matrix system at time step n, in kg / (m³). 2 ·s); C n+1 Carbon dioxide concentration at time step n+1, in mol / L; m is the amount of oil phase i component exchanged between the artificial fracture system and the matrix system due to pressure difference at time step n+1. 3 / s;x i For the i-th grid in the x-direction; for the y-direction... j For the j-th grid in the y-direction; z k For the k-th grid in the z-direction; φ m Porosity of the matrix system, %; ρ om For the oil phase density of the matrix system, 10 3 kg / m 3 S om The saturation of component i in the oil phase of the matrix system, in %;

[0172] The differential introduction amount of gas phase component i at time step n of the matrix system. Let be the gas phase density of the matrix system at time step n, 10 3 kg / m 3 ; m represents the amount of gas phase exchanged between the artificial fracture system and the matrix system caused by the pressure difference at time step n+1. 3 / s;ρ gm For the gas phase density of the matrix system, 10 3 kg / m 3 S gm The saturation of component i in the gas phase of the matrix system, in %;

[0173] The amount of water phase differentially introduced at time step n in the matrix system. Let be the aqueous phase density of the matrix system at time step n, 10 3 kg / m 3 ; m represents the amount of water phase exchanged between the artificial fracture system and the matrix system due to pressure difference at time step n+1. 3 / s;S wm The water saturation level in the matrix system is expressed as %, ρ. wm The density of the aqueous phase in the matrix system is 10. 3 kg / m 3 S wm The water saturation level in the matrix system is expressed as %.

[0174] and These represent the differential introduction amounts of oil phase i component in the matrix system along the x, y, and z directions at time step n, respectively. and When n time steps and Oil phase initiation pressure gradient at the grid; and When n time steps and Oil phase initiation pressure gradient at the grid; and When n time steps and Oil phase initiation pressure gradient at the grid; and respectively in the x direction and At the grid; and respectively in the y direction and At the grid; and respectively in the z direction and At the grid;

[0175] and These represent the differential introduction amounts of the i-th gas phase component of the matrix system in the x, y, and z directions at time step n, respectively. n-time step gas phase start-up pressure gradient; When n time steps and Vapor phase initiation pressure gradient at the grid;

[0176] and These represent the differential introduction amounts of the aqueous phase i component of the matrix system in the x, y, and z directions at time step n, respectively. When n time steps and Water phase initiation pressure gradient at the grid.

[0177] The three-dimensional difference equations for the oil, gas, and water phases of the artificial fracture system are as follows:

[0178]

[0179] In the formula,

[0180]

[0181]

[0182]

[0183]

[0184] in, The differential introduction amount of oil phase i component in the artificial fracture system at time step n; Let be the oil phase density at time step n of the artificial fracture system, 10 3 kg / m 3 ;q oi m represents the amount of oil phase i component artificially extracted in the flow unit. 3 / s; Let be the mass diffusion flux of carbon dioxide into the oil phase of the artificial fracture system at time step n, kg / (m³). 2 ·s); φ f Porosity of the artificial fracture system, %; ρ of The density of the oil phase in the artificial fracture system is 10. 3 kg / m 3 S of The saturation of oil phase i component in the artificial fracture system, in %;

[0185] The differential introduction amount of gas phase i component in the artificial fracture system at time step n; Let n be the gas phase density in the artificial fracture system at time step n, 10 3 kg / m 3 ;q gi m represents the difference in artificial injection and production of gas phase i component in the flow unit. 3 / s;ρ gf The gas phase density in the artificial fracture system is 10. 3 kg / m 3 S gf Let represent the saturation level of gas phase i component in the artificial fracture system, in %;

[0186] The amount of water phase differential introduced into the artificial fracture system; Let be the water phase density in the artificial fracture system at time step n, 10 3 kg / m 3 ;q w The difference between water phase artificial injection and production in the flow unit, m 3 / s;ρ wf The density of the water phase in the artificial fracture system, 10 3 kg / m 3 S wf The water saturation level in the artificial fracture system is expressed as %.

[0187] and The differential introduction amounts of oil phase i component in the artificial fracture system at time steps n (x, y, and z) are respectively. and These represent the differential introduction amounts of gas phase i component in the artificial fracture system along the x, y, and z directions at time step n, respectively. n-time step gas phase start-up pressure gradient; and These represent the differential introduction amounts of the i-th component of the aqueous phase in the artificial fracture system along the x, y, and z directions at time step n.

[0188] like Figure 3 As shown in the embodiments of this specification, before step S160: calculating the production capacity of the tight oil reservoir using the three-dimensional difference equations of the oil, gas, and water phases of the matrix system and the artificial fracture system, the method further includes:

[0189] S310: Establish a production well model for carbon dioxide-water-gas alternating flooding in tight oil reservoirs.

[0190] S320: Input the production well data and simulation parameter data into the production well model.

[0191] The input production well data can include well type data, injection parameters, and production parameters; the simulation parameter data can include grid parameters, molecular diffusion coefficient, phase permeability coefficient, PVT (i.e., pressure, volume, and temperature) data.

[0192] S330: Run the production well model to obtain the pressure field distribution, oil, gas and water composition and saturation field distribution at each time step until the simulation production ends.

[0193] S340: Using the production well model to simulate the output data at the end of production, the three-dimensional difference equations of oil, gas, and water in the matrix system and artificial fracture system are verified.

[0194] The output data may include at least cumulative oil production, cumulative water production, and gas-oil ratio. For example... Figure 4 The diagram shown is a comparison and verification diagram of the cumulative oil production output data obtained using the Eclipse production well model and the cumulative oil production capacity data calculated using the three-dimensional difference equations of the oil, gas, and water phases using the matrix system and artificial fracture system in the embodiments of this specification. Figure 5 The diagram shown is a comparison and verification schematic of the gas-oil ratio output data obtained using the Eclipse production well model and the gas-oil ratio production capacity data calculated using the three-dimensional difference equations of the oil, gas, and water phases in the embodiments of this specification. Figure 4 and Figure 5 As shown, the cumulative oil production data calculated by the three-dimensional difference equation is higher than the output data calculated by the Eclipse production well model. This is mainly because the Eclipse production well model does not consider factors such as carbon dioxide diffusion and mass transfer, dissolution and viscosity reduction, and expansion of crude oil volume. Simultaneously, since the three-dimensional difference equation obtained by this method considers the diffusion effect of carbon dioxide in reservoirs affected by and unaffected by water drive, the calculated production gas-oil ratio is also higher than the simulation results of the Eclipse production well model. Therefore, the method for calculating the production capacity of tight oil reservoirs using carbon dioxide-water-gas alternating flooding provided in the embodiments of this specification can more realistically and accurately reflect the seepage law and production characteristics of tight oil reservoirs using carbon dioxide-water-gas alternating flooding.

[0195] like Figure 6 As shown in the embodiments of this specification, a device for calculating the production capacity of a tight oil reservoir using a carbon dioxide-water-gas alternating flooding method is also provided. The device includes:

[0196] The first module 61 is used to establish the three-phase continuity equations of oil, gas and water for the matrix system and the artificial fracture system respectively, based on the law of conservation of mass.

[0197] The second module 62 is used to establish the motion equations of the matrix system and the artificial fracture system, respectively, taking into account the initiation pressure gradient, capillary pressure and gravity factors.

[0198] The third module 63 is used to establish auxiliary equations, which include at least the three-phase flow equations of oil, gas and water, the molecular diffusion equation of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase interpenetration equations of oil, gas and water considering the lag of interpenetration.

[0199] Solver module 64 is used to obtain the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, based on the continuity equation, the motion equation and the auxiliary equation, respectively.

[0200] Discrete processing module 65 is used to discretize the seepage differential equations of the matrix system and the artificial fracture system using the finite difference method, and solve for the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system.

[0201] The calculation module 66 is used to calculate the production capacity of the tight oil reservoir by carbon dioxide-water-gas alternating flooding injection and production based on the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system.

[0202] The beneficial effects obtained by the apparatus provided in the embodiments of this specification are consistent with the beneficial effects obtained by the methods described above, and will not be repeated here.

[0203] like Figure 7 The illustration shows a computer device provided in an embodiment of this specification. The tight oil reservoir carbon dioxide-water-gas alternating flooding production capacity calculation device provided in this specification can be the computer device in this embodiment, executing the methods described above. The computer device 702 may include one or more processors 704, such as one or more central processing units (CPUs), each processing unit capable of implementing one or more hardware threads. The computer device 702 may also include any memory 706 for storing information of any kind, such as code, settings, data, etc. Non-limitingly, for example, the memory 706 may include any type of RAM, any type of ROM, flash memory, hard disk, optical disk, etc. More generally, any memory can use any technology to store information. Further, any memory can provide volatile or non-volatile retention of information. Further, any memory can represent a fixed or removable component of the computer device 702. In one case, when the processor 704 executes associated instructions stored in any memory or combination of memories, the computer device 702 can perform any operation of the associated instructions. The computer device 702 also includes one or more drive mechanisms 708 for interacting with any memory, such as a hard disk drive mechanism, an optical disk drive mechanism, etc.

[0204] Computer device 702 may also include an input / output module 710 (I / O) for receiving various inputs (via input device 712) and providing various outputs (via output device 714). A specific output mechanism may include a presentation device 716 and an associated graphical user interface (GUI) 718. In other embodiments, the input / output module 710 (I / O), input device 712, and output device 714 may be omitted, and the device may function solely as a computer device within a network. Computer device 702 may also include one or more network interfaces 720 for exchanging data with other devices via one or more communication links 722. One or more communication buses 724 couple the components described above together.

[0205] Communication link 722 can be implemented in any way, such as via a local area network, a wide area network (e.g., the Internet), a point-to-point connection, or any combination thereof. Communication link 722 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc., governed by any protocol or combination of protocols.

[0206] Corresponding to, for example Figures 1 to 3 In addition to the method shown, embodiments of this specification also provide a computer-readable storage medium storing a computer program that, when executed by a processor, performs the steps of the above-described method.

[0207] This specification also provides computer-readable instructions, wherein when a processor executes the instructions, the program therein causes the processor to perform the following... Figures 1 to 3 The method shown.

[0208] This specification also provides a computer program product, including at least one instruction or at least one program segment, wherein the at least one instruction or the at least one program segment is loaded and executed by a processor to achieve the following: Figures 1 to 3 The method shown.

[0209] It should be understood that in the various embodiments of this specification, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this specification.

[0210] It should also be understood that, in the embodiments of this specification, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this specification generally indicates that the preceding and following related objects have an "or" relationship.

[0211] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this specification can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this specification.

[0212] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0213] In the several embodiments provided in this specification, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and 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 couplings or direct couplings or communication connections shown or discussed may be indirect couplings or communication connections through some interfaces, devices, or units, or they may be electrical, mechanical, or other forms of connection.

[0214] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments described in this specification, depending on actual needs.

[0215] Furthermore, the functional units in the various embodiments of this specification can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0216] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this specification, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this specification. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0217] This specification uses specific embodiments to illustrate the principles and implementation methods of this specification. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this specification. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this specification. Therefore, the content of this specification should not be construed as a limitation of this specification.

Claims

1. A method for calculating the productivity of carbon dioxide-water-gas alternating flooding in tight oil reservoirs, characterized in that, include: Based on the law of conservation of mass, three-phase continuity equations for oil, gas, and water are established for both the matrix system and the artificial fracture system. Considering the initiation pressure gradient, capillary pressure, and gravity, the equations of motion for the matrix system and the artificial fracture system are established respectively. Establish auxiliary equations, which include at least the three-phase crossflow equation of oil, gas and water, the molecular diffusion equation of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase cross-permeability equation of oil, gas and water considering the lag of cross-permeability. Based on the continuity equation, the motion equation, and the auxiliary equation, the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, are obtained. The seepage differential equations of the matrix system and the artificial fracture system were discretized using the finite difference method, and the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system were obtained by solving them. Based on the three-dimensional difference equations of oil, gas, and water in the matrix system and artificial fracture system, the production capacity of the tight oil reservoir through alternating carbon dioxide-water-gas flooding and production is calculated. The three-phase continuity equation for the matrix system (oil, gas, and water) is as follows: in, For Hamiltonian operators, The density of the oil phase in the matrix system, The oil phase flow velocity in the matrix system, For the oil phase in the matrix system Component mass content Let be the volume factor of the oil phase in the matrix system. The artificial fracture system and the oil phase of the matrix system caused by pressure difference The exchange capacity of the components For the porosity of the matrix system, For the oil phase in the matrix system Component saturation This represents the mass diffusion flux of carbon dioxide into the oil phase of the matrix system. The amount of oil phase components; The density of the gas phase in the matrix system. The vapor flow velocity in the matrix system, For the gas phase in the matrix system Component mass content Let be the volume factor of the gas phase in the matrix system. The cracks are caused by pressure difference and are connected to the gas phase of the matrix system. The exchange capacity of the components For the gas phase in the matrix system Component saturation The quantity of gaseous components; The density of the aqueous phase in the matrix system, The aqueous phase permeation velocity in the matrix system, The volume coefficient of the aqueous phase in the matrix system; The amount of water exchanged between the artificial fracture system and the matrix system due to pressure difference. This represents the water saturation level in the matrix system. The three-phase continuity equation for oil, gas, and water in an artificial fracture system is as follows: in, The density of the oil phase in the artificial fracture system. The oil phase flow velocity in the artificial fracture system. Oil phase in artificial fracture system Component mass content This refers to the oil phase volume factor in the artificial fracture system. Oil phase in the flow unit Components extracted manually This represents the mass diffusion flux of carbon dioxide into the oil phase of the artificial fracture system. For the porosity of the artificial fracture system, Oil phase in artificial fracture system Component saturation; The gas phase density in the artificial fracture system. The vapor flow velocity in the artificial fracture system. Gas phase in artificial fracture system Component mass content is the volume coefficient of the gas phase in the artificial fracture system. This refers to the difference between artificial injection and production of gas phase i component in the flow unit. Gas phase in artificial fracture system Component saturation; The density of the water phase in the artificial fracture system. The water phase seepage velocity in the artificial fracture system. The volume coefficient of the water phase in the artificial fracture system. This refers to the difference between artificial injection and production of the aqueous phase in the flow unit. This represents the water saturation level in the artificial fracture system.

2. The method according to claim 1, characterized in that, The equation of motion for the matrix system is: in, The oil phase flow velocity in the matrix system, The absolute permeability of the matrix system. The relative permeability of the oil phase. The viscosity of the oil phase in the matrix system. For Hamiltonian operators, For the oil phase pressure of the matrix system, For the oil phase start-up pressure gradient, The density of the oil phase in the matrix system, It is the acceleration due to gravity. The difference in height; The vapor flow velocity in the matrix system, The relative permeability of the gas phase. The viscosity of the gas phase in the matrix system. For the gas phase pressure of the matrix system, For the gas phase initiation pressure gradient, This represents the gas phase density in the matrix system. The aqueous phase permeation velocity in the matrix system, The relative permeability of the aqueous phase. The viscosity of the aqueous phase in the matrix system, For the aqueous phase pressure of the matrix system, To initiate the pressure gradient in the aqueous phase, The density of the aqueous phase in the matrix system; The equation of motion for the artificial fracture system is: in, The oil phase flow velocity in the artificial fracture system. The absolute permeability of the artificial fracture system. The viscosity of the oil phase in the artificial fracture system. For the oil phase pressure of the artificial fracture system, The density of the oil phase in the artificial fracture system; The vapor flow velocity in the artificial fracture system. The viscosity of the gas phase in the artificial fracture system. The gas phase pressure of the artificial fracture system. The gas phase density in the artificial fracture system; The water phase seepage velocity in the artificial fracture system. The viscosity of the aqueous phase in the artificial fracture system. For the water phase pressure of the artificial fracture system, The density of the water phase in the artificial fracture system is given.

3. The method according to claim 1, characterized in that, The equation for the three-phase flow of oil, gas, and water is as follows: in, This refers to the amount of oil phase i component exchanged between the artificial fracture system and the matrix system due to pressure differential. The shape factor represents the contact area between cracks and bedrock per unit volume of rock. For the oil phase in the matrix system Component mass content The absolute permeability of the matrix system. The relative permeability of the oil phase. Oil phase viscosity, Let be the volume factor of the oil phase in the matrix system. For the oil phase pressure in the matrix system, This refers to the oil phase pressure in the artificial fracture system. This refers to the amount of gas phase i-component exchanged between the artificial fracture system and the matrix system due to pressure difference. For the gas phase in the matrix system Component mass content The relative permeability of the gas phase. The viscosity is the gas phase viscosity. Let be the volume factor of the gas phase in the matrix system. The gas phase pressure in the matrix system, This refers to the gas phase pressure in the artificial fracture system. This refers to the amount of water phase exchanged between the artificial fracture system and the matrix system due to pressure difference. The relative permeability of the aqueous phase. The viscosity of the aqueous phase is... The volume coefficient of the aqueous phase in the matrix system, For the pressure of the aqueous phase in the matrix system, The pressure of the water phase in the artificial fracture system.

4. The method according to claim 3, characterized in that, The shape factor is calculated using the following formula: in, For the matrix system in Length in direction, For the matrix system in Length in direction, For the matrix system in The length of the direction.

5. The method according to claim 1, characterized in that, The molecular diffusion equation is as follows: in, This represents the mass diffusion flux of carbon dioxide in crude oil within the matrix system. This represents the mass diffusion flux of carbon dioxide in crude oil within an artificial fracture system. Here is the molar mass of carbon dioxide; This represents the molar concentration of carbon dioxide in the crude oil of the matrix system. This represents the molar concentration of carbon dioxide in crude oil within an artificial fracture system. For Hamiltonian operators, is the carbon dioxide diffusion coefficient.

6. The method according to claim 5, characterized in that, The carbon dioxide diffusion coefficient includes the diffusion coefficient of carbon dioxide when diffusing in a reservoir affected by water drive and the diffusion coefficient when diffusing in a reservoir not affected by water drive. The diffusion coefficient of carbon dioxide when diffusing in a reservoir affected by water drive is calculated by the following formula: in, This represents the diffusion molar amount of carbon dioxide in a water-driven reservoir. Coordinates of the reservoir affected by water drive exist The concentration of carbon dioxide at any given time. This represents the initial concentration of carbon dioxide during diffusion in a water-driven reservoir. This is the sum of the lengths of the reservoirs affected by waterflooding and those not affected by waterflooding. denoted as the diffusion coefficient of carbon dioxide during diffusion in a water-driven reservoir. Reservoir tortuosity Reservoir porosity; The diffusion coefficient of carbon dioxide in a reservoir unaffected by water flooding is calculated using the following formula: in, This represents the diffusion molar amount of carbon dioxide in a reservoir unaffected by water flooding. This represents the initial concentration of carbon dioxide during diffusion in a reservoir unaffected by water flooding. is the diffusion coefficient of carbon dioxide when it diffuses in a reservoir unaffected by water drive.

7. The method according to claim 1, characterized in that, Before calculating the production capacity of the tight oil reservoir using the three-dimensional difference equations of the oil, gas, and water phases based on the matrix system and the artificial fracture system, the method further includes: Establish a production well model for carbon dioxide-water-gas alternating flooding in tight oil reservoirs; Input the production well data and simulation parameter data into the production well model; Run the production well model to obtain the pressure field distribution, oil, gas and water composition and saturation field distribution at each time step until production ends; The three-dimensional difference equations of oil, gas, and water in the matrix system and artificial fracture system are verified using the output data at the end of the production well model.

8. A device for calculating the productivity of a tight oil reservoir using a carbon dioxide-water-gas alternating flooding method, characterized in that, The device includes: The first module is used to establish the three-phase continuity equations of oil, gas, and water for the matrix system and the artificial fracture system, respectively, based on the law of conservation of mass. The second module is used to establish the motion equations of the matrix system and the artificial fracture system, taking into account the initiation pressure gradient, capillary pressure and gravity factors. The third module is used to establish auxiliary equations, which include at least the three-phase flow equations of oil, gas and water, the molecular diffusion equation of carbon dioxide in the matrix system and the artificial fracture system, and the three-phase interpenetration equations of oil, gas and water considering the lag of interpenetration. The solution module is used to obtain the seepage differential equations of the matrix system and the artificial fracture system, as well as their initial conditions and internal and external boundary conditions, based on the continuity equation, the motion equation and the auxiliary equation, respectively. The discretization module is used to discretize the seepage differential equations of the matrix system and the artificial fracture system using the finite difference method, and solve them to obtain the three-dimensional difference equations of oil, gas and water in the matrix system and the artificial fracture system. The calculation module is used to calculate the production capacity of the tight oil reservoir based on the three-dimensional difference equations of the oil, gas and water phases of the matrix system and the artificial fracture system; The three-phase continuity equations for oil, gas, and water in the matrix system constructed by the first module are as follows: in, For Hamiltonian operators, The density of the oil phase in the matrix system, The oil phase flow velocity in the matrix system, For the oil phase in the matrix system Component mass content Let be the volume factor of the oil phase in the matrix system. The artificial fracture system and the oil phase of the matrix system caused by pressure difference The exchange capacity of the components For the porosity of the matrix system, For the oil phase in the matrix system Component saturation This represents the mass diffusion flux of carbon dioxide into the oil phase of the matrix system. The amount of oil phase components; The density of the gas phase in the matrix system. The vapor flow velocity in the matrix system, For the gas phase in the matrix system Component mass content Let be the volume factor of the gas phase in the matrix system. The cracks are caused by pressure difference and are connected to the gas phase of the matrix system. The exchange capacity of the components For the gas phase in the matrix system Component saturation The quantity of gaseous components; The density of the aqueous phase in the matrix system, The aqueous phase permeation velocity in the matrix system, The volume coefficient of the aqueous phase in the matrix system; The amount of water exchanged between the artificial fracture system and the matrix system due to pressure difference. This represents the water saturation level in the matrix system. The three-phase continuity equation for oil, gas, and water in an artificial fracture system is as follows: in, The density of the oil phase in the artificial fracture system. The oil phase flow velocity in the artificial fracture system. Oil phase in artificial fracture system Component mass content This refers to the oil phase volume factor in the artificial fracture system. Oil phase in the flow unit Components extracted manually This represents the mass diffusion flux of carbon dioxide into the oil phase of the artificial fracture system. For the porosity of the artificial fracture system, Oil phase in artificial fracture system Component saturation; The gas phase density in the artificial fracture system. The vapor flow velocity in the artificial fracture system. Gas phase in artificial fracture system Component mass content is the volume coefficient of the gas phase in the artificial fracture system. This refers to the difference between artificial injection and production of gas phase i component in the flow unit. Gas phase in artificial fracture system Component saturation; The density of the water phase in the artificial fracture system. The water phase seepage velocity in the artificial fracture system. The volume coefficient of the water phase in the artificial fracture system. This refers to the difference between artificial injection and production of the aqueous phase in the flow unit. This represents the water saturation level in the artificial fracture system.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 7.

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