Treatment method for chemical reaction and viscosity change in CO2 storage and oil displacement

Abstract

The invention relates to the technical field of oil exploration and development, and particularly provides a treatment method for chemical reaction and viscosity change in CO2 storage and oil displacement. The method comprises the following steps: constructing a flow state physical model after CO2 enters a reservoir; chemical reaction between CO2 and stratum minerals is dissolved into an oil phase, and the change of viscosity of the oil phase is applied to a state equation in the form of a formula, so that a three-phase formula is obtained; obtaining a limited number of grid nodes according to a three-phase formula, and replacing a continuous solution domain with the limited number of grid nodes; according to the solution domain, calculating to obtain a relation expression of CO2 saturation changing along with radius and time; according to the method, distribution of CO2 in the oil-gas two phases in the displacement process, dissolution of CO2 in water in the storage process and the reaction condition under the special formation condition are simulated at the same time, and the CO2 emission reduction effect and potential can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 storage and oil recovery, and in particular to a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery. Background Art

[0002] Carbon capture, utilization and storage (CCUS) technology is one of the key technologies for reducing CO2 emissions and mitigating the greenhouse effect. Compared with CO2 energy conservation and emission reduction, CCUS technology has great effect and potential for reducing CO2 emissions as long as the storage method and storage location are properly selected. According to the statistical results of relevant industry data, a total of 136 mine field tests to achieve CO2 injection to improve oil recovery have been carried out worldwide, of which 88 have achieved significant oil and gas resource increases, with a success rate of nearly 65%, indicating that CO2 oil recovery has good effects and application prospects. In order to better understand the mechanism and influencing factors of CO2 oil recovery, optimize oil recovery plans, improve oil recovery, reduce costs, extend the life of oil fields, and solve problems that cannot be solved by experiments. Numerical simulation related to CO2 storage and oil recovery has become one of the key technologies in the development of oil and gas fields. It is a very meaningful work to study the mathematical models involved in the numerical simulation of CO2 storage and oil recovery.

[0003] Most reservoir numerical simulation software can simulate the CO2 displacement process, but in the entire simulation process, it is impossible to accurately consider the presence of CO2 as one of the hydrocarbon components in the oil and gas phases, as well as the effects of CO2 dissolution in water, chemical reactions between carbonic acid and formation minerals, and mineralization processes on reservoir permeability. At the same time, some commercial numerical simulation software can simulate the CO2 burial process alone, simulating burial mechanisms such as dissolution in water and mineral precipitation, but cannot calculate the CO2 dissolution and displacement process in the oil phase. Summary of the invention

[0004] In view of this, the present invention provides a method for processing chemical reactions and viscosity changes in CO2 storage and oil displacement, which is used to simultaneously simulate the distribution of CO2 in the oil and gas phases during the displacement process, the dissolution of CO2 in water during the storage process, and the reaction under special formation conditions, so as to improve the effect and potential of CO2 emission reduction.

[0005] In a first aspect, the present invention provides a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery, the method comprising: Step 1: Construct a physical model of the flow state of CO2 after it enters the reservoir; Step 2: Based on the flow state physical model of step 1, combined with Darcy's seepage theory and mass conservation theory, the chemical reaction between CO2 and formation minerals and the change in oil phase viscosity caused by dissolving into the oil phase are applied in the state equation in the form of a formula, and a seepage model of CO2 entering the reservoir is established. In a radial one-dimensional cylindrical coordinate system, the mass continuity equation is used to calculate the water phase, oil phase and CO2 liquid phase respectively, and the water phase formula, oil phase formula and CO2 gas phase formula are obtained; Step 3: According to the water phase formula, oil phase formula and CO2 gas phase formula in step 2, the calculation area is divided into differential grids to obtain a finite number of grid nodes, and the finite number of grid nodes are used to replace the continuous solution domain; Step 4: Based on the solution domain in step 3, calculate and obtain the relationship between CO2 saturation, radius and time; Step 5: Form a prediction model by changing the relationship, input the CO2 injection volume, injection pressure, and reservoir parameters, and predict the CO2 storage or oil recovery status.

[0006] Optionally, the step 2 includes: The dissolution of CO2 in water during the storage process, the special reaction between the generated carbonic acid and the formation minerals, and the change of formation porosity due to geochemical reactions during the mineralization process; the change law of formation medium porosity with effective volume strain is: ; (1) in is the effective volume strain, is the geochemical volume strain, is the adsorption strain, is the pore pressure induced strain, is the volume strain; and are the initial porosity and current porosity, respectively; For initial , in the initial state, both the volume strain and the chemical volume strain are zero; is the initial pore pressure; for , formula (1) is simplified to: ; (2) According to formula (2), the formation porosity is affected by the volume strain of the formation medium and is related to the pore pressure, geochemical volume strain and adsorption-induced volume strain.

[0007] Optionally, the step 2 further includes: The effect of formation pressure on crude oil viscosity is decomposed into two parts, namely, the effect of pressure change on viscosity when there is no CO2 dissolution and the effect of pressure change on crude oil viscosity when CO2 dissolves and precipitates in crude oil; the reactions of these two parts to pressure changes are inconsistent, which leads to the emergence of saturation pressure; when the pressure is higher than the saturation pressure, the effect of crude oil volume on crude oil viscosity accounts for the main part, and the volume of crude oil will decrease with the increase of pressure, resulting in increased viscosity; and when the pressure is lower than the saturation pressure, the effect of CO2 dissolution in crude oil on crude oil viscosity accounts for the main part, and as the pressure decreases, dissolved gas will overflow from the crude oil, causing the heavy hydrocarbon components to condense, thus showing a sharp increase in viscosity; the relationship between viscosity and saturation is developed as follows: ; (3) in, ， ， ， is the coefficient by which crude oil viscosity changes with the solubility of gas in the crude oil.

[0008] Optionally, the step 4 includes: According to the solution domain, the time t is discretized, from arrive In time, we get: ; ; ; After finishing, we can get: ; ; ; make ; It is the slope of saturation changing with time, which is a function of saturation and complies with the upstream weight method; after each pressure is calculated, a small step of MT is used. To calculate the saturation [S], the adaptive time step method .

[0009] In a second aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored program, wherein when the program is run, the device where the computer-readable storage medium is located is controlled to execute a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery in the first aspect or any possible implementation of the first aspect.

[0010] In a third aspect, an embodiment of the present invention provides an electronic device, comprising: one or more processors; a memory; and one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs include instructions, which, when executed by the device, enable the device to execute a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery in the first aspect or any possible implementation of the first aspect.

[0011] In the technical solution provided by the present invention, the method comprises constructing a physical model of the flow state after CO2 enters the reservoir; according to the physical model of the flow state, in combination with Darcy's seepage theory and mass conservation theory, applying the chemical reaction between CO2 and formation minerals and the change of oil phase viscosity caused by dissolving CO2 into the oil phase in the form of a formula to the state equation, establishing a seepage model for CO2 entering the reservoir, and calculating the water phase, oil phase and CO2 liquid phase respectively by the mass continuity equation in a radial one-dimensional cylindrical coordinate system to obtain the water phase formula, oil phase formula and CO2 gas phase formula; according to the water phase formula, oil phase formula and CO2 gas phase formula, 2 gas phase formula, the calculation area is divided into differential grids to obtain a finite number of grid nodes, and the finite number of grid nodes is used to replace the continuous solution domain; according to the solution domain, the relationship between CO2 saturation, radius and time is calculated; a prediction model is formed by changing the relationship, and the CO2 injection volume, injection pressure, and reservoir parameters are input to predict the CO2 storage or oil displacement state. This method realizes the simultaneous simulation of the distribution of CO2 in the oil and gas phases during the displacement process, the dissolution of CO2 in water during the storage process, and the reaction under special formation conditions, which can effectively improve the effect and potential of CO2 emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 A flowchart of a processing method provided by an embodiment of the present invention; Figure 2 A schematic diagram of grid and unit division and numbering provided in an embodiment of the present invention; Figure 3 The water saturation before and after correction by applying geophysical and chemical reactions provided in an embodiment of the present invention; Figure 4 The oil saturation before and after correction by applying geophysical and chemical reactions provided in an embodiment of the present invention; Figure 5 CO2 saturation before and after correction of geophysical and chemical reactions provided by an embodiment of the present invention; Figure 6 The water saturation before and after the applied viscosity fitting correction provided by the embodiment of the present invention; Figure 7 The oil saturation before and after the applied viscosity fitting correction provided by the embodiment of the present invention; Figure 8 CO2 saturation before and after correction of applied viscosity fitting provided by an embodiment of the present invention; Fig. 9 A schematic diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] It should be clear that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention are also intended to include plural forms, unless the context clearly indicates other meanings.

[0017] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0018] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0019] Figure 1 A flowchart of a processing method provided by an embodiment of the present invention, such as Figure 1 As shown, the method includes: Step 1: Construct a physical model of the flow state of CO2 after it enters the reservoir.

[0020] In the embodiment of the present invention, the flow state is the seepage driven by the pressure difference between the wellbore and the formation. Physical model of flow state: 1. Conforms to Darcy's seepage law; 2. Isothermal seepage; 3. Oil, gas and water three phases and oil, gas and water three components, the water component exists in the water phase, the oil component exists in the oil phase, and the oil and water phases are immiscible; the gas component not only exists in the gas phase, but also dissolves in the oil phase and the water phase; 4. One-dimensional flow; 5. Both rock and fluid are compressible; 6. The reservoir is heterogeneous and anisotropic; 7. Capillary force and gravity are not considered.

[0021] Step 2: Based on the flow state physical model of step 1, combined with Darcy's seepage theory and mass conservation theory, the chemical reaction between CO2 and formation minerals and the change in oil phase viscosity caused by dissolution into the oil phase are applied in the state equation in the form of a formula, and a seepage model of CO2 entering the reservoir is established. In the radial one-dimensional cylindrical coordinate system, the mass continuity equation is used to calculate the water phase, oil phase and CO2 liquid phase respectively, and the water phase formula, oil phase formula and CO2 gas phase formula are obtained.

[0022] In the embodiment of the present invention, step 2 includes: The dissolution of CO2 in water during the storage process, the special reaction between the generated carbonic acid and the formation minerals, and the change of formation porosity due to geochemical reactions during the mineralization process; the change law of formation medium porosity with effective volume strain is: ; (1) in is the effective volume strain, is the geochemical volume strain, is the adsorption strain, is the pore pressure induced strain, is the volume strain; and are the initial porosity and current porosity, respectively; For initial , in the initial state, both the volume strain and the chemical volume strain are zero; is the initial pore pressure; for , formula (1) is simplified to: ; (2) According to formula (2), the formation porosity is affected by the volume strain of the formation medium and is related to the pore pressure, geochemical volume strain and adsorption-induced volume strain.

[0023] In the embodiment of the present invention, step 2 further includes: CO2 is easily soluble in crude oil, which significantly reduces the viscosity of crude oil. The greater the initial viscosity of crude oil, the more obvious the range of its decrease. The main function of CO2 in reducing the viscosity of crude oil is to improve the fluidity of crude oil, so that a small amount of displacement agent can achieve a certain oil displacement efficiency; or a certain amount of displacement agent can achieve a higher displacement effect.

[0024] The effect of formation pressure on crude oil viscosity is decomposed into two parts, namely, the effect of pressure change on viscosity when there is no CO2 dissolution and the effect of pressure change on crude oil viscosity when CO2 dissolves and precipitates in crude oil; the reactions of these two parts to pressure changes are inconsistent, which leads to the emergence of saturation pressure; when the pressure is higher than the saturation pressure, the effect of crude oil volume on crude oil viscosity accounts for the main part, and the volume of crude oil will decrease with the increase of pressure, resulting in increased viscosity; and when the pressure is lower than the saturation pressure, the effect of CO2 dissolution in crude oil on crude oil viscosity accounts for the main part, and as the pressure decreases, dissolved gas will overflow from the crude oil, causing the heavy hydrocarbon components to condense, thus showing a sharp increase in viscosity; the relationship between viscosity and saturation is developed as follows: ; (3) in, ， ， ， is the coefficient by which crude oil viscosity changes with the solubility of gas in the crude oil.

[0025] At the center of the unit body, point O, along the direction of reservoir flow, the seepage velocity of free gas under standard conditions is , the seepage velocity of gas dissolved in oil and water under standard conditions is , ,in , is the dissolved gas-oil ratio, dissolved gas-water ratio; Under standard conditions, CO2 gas phase In time along x The difference in the gas mass flowing into and out of the unit cell in the direction is expressed as: ; exist The mass increment of the standard volume gas in the unit body within a certain time period is expressed as: ; The mass conservation equation of the gas component is expressed as: ; That is: ; During the oil displacement process, the three-phase fluid of oil, gas and water flows in the porous medium, and the flow obeys Darcy's law. The equation form of Darcy's law in the Cartesian coordinate system is: ; Substituting into the mass conservation equation of the gas component, the CO2 gas phase expression can be obtained as follows: ; Similarly, the oil phase expression can be obtained as follows: ; The aqueous phase expression is: .

[0026] Step 3: According to the water phase formula, oil phase formula and CO2 gas phase formula in step 2, the calculation area is divided into differential grids to obtain a finite number of grid nodes, and the finite number of grid nodes are used to replace the continuous solution domain.

[0027] In the embodiment of the present invention, step three includes: Assuming that capillary forces are neglected, , and order , , ; Substituting the above into the oil phase formula, water phase formula and CO2 gas phase formula, we can get: ; make , , , where the density , gas solubility , porosity are all functions of pressure P. , , The derivatives in are expanded according to time, and we can get: ; ; ; There are ,so We can get: ; Available through To eliminate , Then there is only one unknown quantity in the formula that needs to be solved : ; in, ; ; ; ; ; ; ; ; Then the oil phase formula, water phase formula and CO2 gas phase formula can be multiplied by the corresponding coefficients on the left and added to obtain: ; (7) No. The gas phase of unit number, the mass of gas passing through cylinder j is: ; The mass of gas passing through cylinder j-1 is: ; The gas mass increment of unit j is: ; The volume of unit j is: ; Then for the above formula (7), we can get: ; The proof is as follows: ; Similarly, we can get: ; (8) ; (9) ; (10) Then formula (7) is discretized for time t, from arrive In the time; for the radius r discretization, from arrive ;get: ; have to: ; have to: ; Logarithmic transformation in the radial direction Then discretize it, and get: ; After finishing, we can get: ; (11) For the total grid divided, the pressure of the N-1th unit is calculated, and the pressure of the Nth unit adopts the formation pressure.

[0028] In the embodiment of the present invention, a finite number of grid nodes replaces a continuous solution domain to construct a matrix for solving pressure by using the obtained equation for solving pressure, such as Figure 2 The grid and unit division and numbering shown are as follows: the unit number is 1 to N, the node number is 0 to N, and the radius r Discretize into x , which is the radius r 0 to r N Corresponding to the discretized x 0 to x N ; For each unit, the physical quantity to be solved is the three-phase permeability on the boundary K r Right now K r*0 to K r*N , three-phase pressure P Right now P 1 to P N-1 , pressure difference DP Right now DP 0 to DP N-1 , and three-phase saturation S Right now S *1 to S *N-1 ,in S w0 is the water phase saturation in the wellbore, which is 0; S o0 is the oil phase saturation in the wellbore, which is 0; S g0 is the gas saturation in the wellbore, which is 1; this is an explanation of the construction of parameters in the matrix equation. The upstream weight method is used to determine the relative permeability, so that the pressure at time n can be solved by the pressure at time n-1, and then the pressure difference, saturation and permeability can be solved.

[0029] The general formula for pressure solution is derived from the oil phase formula, water phase formula and CO2 gas phase formula to obtain the pressure solution equation for each unit. The pressure solution equations of all units are combined to form a pressure solution matrix, thereby solving the pressure of each unit. Unit division: Discretization on radial radius r , forming a unit sequence .

[0030] Step 4: Based on the solution domain in step 3, calculate and obtain the relationship between CO2 saturation, radius and time.

[0031] In the embodiment of the present invention, step 4 includes: According to the solution domain, substitute formulas (8), (9), and (10) into formulas (4), (5), and (6), and discretize time t, from arrive In time, we get: ; ; ; After finishing, we can get: ; ; ; make ; It is the slope of saturation changing with time, which is a function of saturation and complies with the upstream weight method; after each pressure is calculated, a small step of MT is used. To calculate the saturation [S], the adaptive time step method .

[0032] Step 5: Form a prediction model by changing the relationship, input the CO2 injection volume, injection pressure, and reservoir parameters, and predict the CO2 storage or oil recovery status.

[0033] In the embodiment of the present invention, a program is written in combination with a theoretical algorithm to form a prediction model, and the simulation process includes: Set the formation model parameters, such as setting the layer height grid division, simulation time, etc.; set the initial conditions, such as pressure, initial saturation, porosity, etc.; calculate the relative permeability of the three phases of oil, gas and water; solve the pressure P implicitly through the matrix; correct the porosity according to the geophysical and chemical reactions, and apply viscosity fitting correction; solve the saturation of the three phases of oil, gas and water; calculate the time step, and determine the simulation time, and complete the simulation based on the judgment result.

[0034] Depend on Figures 3 to 5It can be seen that the horizontal axis is the displacement radius of the formation, and the vertical axis is the saturation of the three phases of water, oil, and CO2 gas. It can be clearly seen from the saturation curves of the three phases that: the front and rear sections of the water phase saturation curve are roughly unchanged, the middle section curve shifts to the left, and the water phase saturation increases; the front and rear sections of the oil phase saturation curve are roughly unchanged, the middle section curve shifts to the left, and the oil phase saturation increases; the front and rear sections of the CO2 gas phase saturation curve are roughly unchanged, the middle section curve shifts to the left, and the gas phase saturation decreases. During the displacement process, the water and oil phases that dissolved CO2 gas reacted with the formation to expand the formation gap. The continuous erosion of the formation by the water and oil phases caused the water and oil saturations to increase and the CO2 gas saturation to decrease.

[0035] Depend on Figures 6 to 8 It can be seen that the horizontal axis is the displacement radius of the formation, and the vertical axis is the saturation of the three phases of water, oil, and CO2 gas. It can be clearly seen from the saturation curves of the three phases that the front section of the water phase saturation curve moves to the left, the middle section moves roughly to the left, the saturation rise rate increases, and the back end does not change roughly; the front section of the oil phase saturation curve moves to the right, the middle section moves roughly to the right, the saturation rise rate increases, and the back end does not change roughly; the front section of the CO2 gas phase saturation curve moves to the right, the middle section moves roughly to the right, the saturation decrease rate increases, and the back end does not change roughly. CO2 is easily soluble in crude oil, which significantly reduces the viscosity of crude oil, increases the fluidity of crude oil, enhances the efficiency of CO2 oil displacement, increases the displacement radius, and the oil phase saturation curve shifts to the right as a whole; due to the increase in the overall fluidity of the oil phase, the immiscible displacement contact between CO2 gas and crude oil is insufficient, which reduces the peak value of the oil phase saturation. For the water and CO2 gas phases, the increase in oil phase fluidity leads to the acceleration of CO2 immiscible displacement and the increase in the saturation of the water and CO2 gas phases.

[0036] Each step of the embodiment of the present invention may be performed by an electronic device, which includes but is not limited to a mobile phone, a tablet computer, a portable PC, a desktop computer, etc.

[0037] In the technical solution provided by the present invention, the method comprises constructing a physical model of the flow state after CO2 enters the reservoir; according to the physical model of the flow state, in combination with Darcy's seepage theory and mass conservation theory, applying the chemical reaction between CO2 and formation minerals and the change of oil phase viscosity caused by dissolving CO2 into the oil phase in the form of a formula to the state equation, establishing a seepage model for CO2 entering the reservoir, and calculating the water phase, oil phase and CO2 liquid phase respectively by the mass continuity equation in a radial one-dimensional cylindrical coordinate system to obtain the water phase formula, oil phase formula and CO2 gas phase formula; according to the water phase formula, oil phase formula and CO2 gas phase formula, 2 gas phase formula, the calculation area is divided into differential grids to obtain a finite number of grid nodes, and the finite number of grid nodes is used to replace the continuous solution domain; according to the solution domain, the relationship between CO2 saturation, radius and time is calculated; a prediction model is formed by changing the relationship, and the CO2 injection volume, injection pressure, and reservoir parameters are input to predict the CO2 storage or oil displacement state. This method realizes the simultaneous simulation of the distribution of CO2 in the oil and gas phases during the displacement process, the dissolution of CO2 in water during the storage process, and the reaction under special formation conditions, which can effectively improve the effect and potential of CO2 emission reduction.

[0038] An embodiment of the present invention provides a computer-readable storage medium, which includes a stored program, wherein when the program is running, the electronic device where the computer-readable storage medium is located is controlled to execute an embodiment of the above-mentioned method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery.

[0039] Fig. 9 A schematic diagram of an electronic device provided by an embodiment of the present invention, such as Fig. 9 As shown, the electronic device 21 includes: a processor 211, a memory 212, and a computer program 213 stored in the memory 212 and executable on the processor 211. When the computer program 213 is executed by the processor 211, a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery in an embodiment is implemented. To avoid repetition, they are not described one by one here.

[0040] The electronic device 21 includes, but is not limited to, a processor 211 and a memory 212. Those skilled in the art will appreciate that Fig. 9 It is only an example of the electronic device 21 and does not constitute a limitation of the electronic device 21. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the electronic device may also include input and output devices, network access devices, buses, etc.

[0041] The processor 211 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0042] The memory 212 may be an internal storage unit of the electronic device 21, such as a hard disk or memory of the electronic device 21. The memory 212 may also be an external storage device of the electronic device 21, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card (FlashCard), etc. equipped on the electronic device 21. Further, the memory 212 may also include both an internal storage unit of the electronic device 21 and an external storage device. The memory 212 is used to store computer programs and other programs and data required by network devices. The memory 212 may also be used to temporarily store data that has been output or is to be output.

[0043] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating chemical reactions and viscosity changes in CO2 storage and oil recovery, characterized in that: The method comprises: Step 1: Construct a physical model of the flow state of CO2 after it enters the reservoir; Step 2: Based on the flow state physical model of step 1, combined with Darcy's seepage theory and mass conservation theory, the chemical reaction between CO2 and formation minerals and the change in oil phase viscosity caused by dissolving into the oil phase are applied in the state equation in the form of a formula, and a seepage model of CO2 entering the reservoir is established. In a radial one-dimensional cylindrical coordinate system, the mass continuity equation is used to calculate the water phase, oil phase and CO2 liquid phase respectively, and the water phase formula, oil phase formula and CO2 gas phase formula are obtained; Step 3: According to the water phase formula, oil phase formula and CO2 gas phase formula in step 2, the calculation area is divided into differential grids to obtain a finite number of grid nodes, and the finite number of grid nodes are used to replace the continuous solution domain; Step 4: Based on the solution domain in step 3, calculate and obtain the relationship between CO2 saturation, radius and time; Step 5: Form a prediction model by changing the relationship, input the CO2 injection volume, injection pressure, and reservoir parameters, and predict the CO2 storage or oil recovery status.

2. The method according to claim 1, characterized in that The second step comprises: The dissolution of CO2 in water during the storage process, the special reaction between the generated carbonic acid and the formation minerals, and the change of formation porosity due to geochemical reactions during the mineralization process; the change law of formation medium porosity with effective volume strain is: ；（1） in is the effective volume strain, is the geochemical volume strain, is the adsorption strain, is the pore pressure induced strain, is the volume strain; and are the initial porosity and current porosity, respectively; For initial , in the initial state, both the volume strain and the chemical volume strain are zero; is the initial pore pressure; for , formula (1) is simplified to: ；（2） According to formula (2), the formation porosity is affected by the volume strain of the formation medium and is related to the pore pressure, geochemical volume strain and adsorption-induced volume strain.

3. The method according to claim 1, characterized in that The step 2 also includes: The effect of formation pressure on crude oil viscosity is decomposed into two parts, namely, the effect of pressure change on viscosity when there is no CO2 dissolution and the effect of pressure change on crude oil viscosity when CO2 dissolves and precipitates in crude oil; the reactions of these two parts to pressure changes are inconsistent, which leads to the emergence of saturation pressure; when the pressure is higher than the saturation pressure, the effect of crude oil volume on crude oil viscosity accounts for the main part, and the volume of crude oil will decrease with the increase of pressure, resulting in increased viscosity; and when the pressure is lower than the saturation pressure, the effect of CO2 dissolution in crude oil on crude oil viscosity accounts for the main part, and as the pressure decreases, dissolved gas will overflow from the crude oil, causing the heavy hydrocarbon components to condense, thus showing a sharp increase in viscosity; the relationship between viscosity and saturation is developed as follows: ；（3） in, ， ， ， is the coefficient by which crude oil viscosity changes with the solubility of gas in the crude oil.

4. The method according to claim 1, characterized in that: The fourth step comprises: According to the solution domain, the time t is discretized, from arrive In time, we get: ； ； ； After finishing, we can get: ； ； ； make ； It is the slope of saturation changing with time, which is a function of saturation and complies with the upstream weight method; after each pressure is calculated, a small step of MT is used. To calculate the saturation [S], the adaptive time step method .

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is run, the computer-readable storage medium is controlled to execute a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery according to any one of claims 1 to 4.

6. An electronic device, characterized in that: include: one or more processors; Memory; and one or more computer programs, wherein the one or more computer programs are stored in the memory, and the one or more computer programs include instructions, which, when executed by the device, enable the device to perform a method for processing chemical reactions and viscosity changes in CO2 storage and oil recovery as described in any one of claims 1 to 4.

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