Sandstone reservoir water-rock reaction numerical simulation method for potassium-rich fluid environment

Abstract

The invention provides a sandstone reservoir water-rock reaction numerical simulation method for a potassium-rich fluid environment, and relates to the technical field of oil and gas reservoirs, and the method comprises the following steps: obtaining the rock porosity and contained original mineral components of a target area, the activity of each solute component, and the fugacity of each free gas component; secondary mineral components contained in the target area are determined; constructing a plurality of substance reaction models; determining the activity product of the reaction of each substance; obtaining the total corrosion rate of each original mineral component and the total precipitation rate of each secondary mineral component; determining the corrosion amount based on the total corrosion rate of each original mineral component; determining the precipitation amount based on the total precipitation rate of each secondary mineral component; obtaining rock predicted porosity in the target area; and obtaining the rock predicted permeability based on the rock predicted porosity. According to the method, numerical simulation can be accurately carried out on the water-rock reaction of the sandstone reservoir in the potassium-rich fluid environment, so that the accurate rock predicted porosity and rock predicted permeability are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas reservoirs, and in particular to a water-rock reaction numerical simulation method for sandstone reservoirs in a potassium-rich fluid environment. Background Art

[0002] Sandstone reservoirs are one of the most important reservoir types for oil and natural gas accumulation worldwide. Sandstone reservoir quality, specifically porosity and permeability, is a key factor influencing oil and gas accumulation and reserves. Understanding the diagenetic events and physical and chemical mechanisms that occur within underground sandstone reservoirs is crucial for accurately predicting sandstone reservoir quality.

[0003] Traditional research on sandstone diagenesis relies primarily on experimental methods such as petrology, fluid inclusions, and isotopes. In recent years, numerical simulation has been increasingly applied to the study of sandstone diagenesis processes and mechanisms. Diagenetic numerical simulation aims to predict the chemical reaction behavior between sandstone reservoirs (mineral aggregates) and formation water based on an understanding of the chemical thermodynamics and kinetics of single mineral dissolution and precipitation, as well as the laws of mass migration.

[0004] Sandstone reservoir formation water can show strong differences in different regions and different burial depths, which are manifested in significant differences in formation water salinity, pH, ion composition and content. The main components of sandstone reservoir formation water include Na + , K + , Ca 2+ Mg 2+ 、Cl - 、HCO3 - In most areas, K + The content of K is generally between tens and hundreds of milligrams per liter, but in some areas + The content can be as high as 5000-6000 mg / L. + Fluids have a significant impact on the diagenetic evolution path of sandstone. Existing numerical simulations of diagenesis are only for the transformation between single minerals, and the understanding of their chemical behavior is mostly based on experimental data such as petrology, although mineral stable phase diagrams have also been used for K-rich sandstones. + The diagenetic evolution of sandstone in fluids has been studied, but these studies are mostly qualitative and lack the constraints of quantitative chemical thermodynamics and kinetic laws. Summary of the Invention

[0005] The purpose of the present invention is to provide a numerical simulation method for water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment, which can accurately simulate the water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment to obtain accurate rock predicted porosity and rock predicted permeability.

[0006] A numerical simulation method for water-rock reaction in a sandstone reservoir in a potassium-rich fluid environment, comprising:

[0007] Obtain the rock porosity and original mineral components of the target area, as well as the physical properties, specific surface area and equilibrium constants of each original mineral component;

[0008] Obtaining the solute parameters of each solute component in the formation water of the target area, obtaining the activity coefficient of each solute component based on the solute parameters; obtaining the activity of each solute component based on the activity coefficient of each solute component;

[0009] Obtaining free gas parameters of each free gas component in the system, obtaining the fugacity coefficient of the system based on each free gas parameter, using the fugacity coefficient of the system as the fugacity coefficient of each free gas component, and obtaining the fugacity of each free gas component based on the fugacity coefficient of each free gas component; the system is composed of formation water, rock, and rock pores in the target area;

[0010] Determine the secondary mineral components contained in the target area and the physical properties, specific surface area and equilibrium constant of each secondary mineral component, and construct several material reaction models; determine the activity product of each material reaction based on each material reaction model;

[0011] The dissolution rate of each original mineral component in each substance reaction is obtained based on the activity product of each substance reaction, the specific surface area of each original mineral component and the equilibrium constant. The precipitation rate of each secondary mineral component in each substance reaction is obtained based on the activity product of each substance reaction, the specific surface area of each secondary mineral component and the equilibrium constant.

[0012] When the original mineral component or the secondary mineral component is potassium feldspar, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is:

[0013]

[0014] When the original mineral component or the secondary mineral component is non-potassium feldspar, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is:

[0015]

[0016] in, is the dissolution rate of the uth original mineral component or the precipitation rate of the uth secondary mineral component, SA u is the specific surface area of the u-th original mineral component or the u-th secondary mineral component, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under acidic conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under neutral conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under alkaline conditions, E acid is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under acidic conditions, E neutral is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under neutral conditions, E base is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under alkaline conditions, T is the temperature value, Q is the activity product of the material reaction, K u is the equilibrium constant of the uth original mineral component or the uth secondary mineral component, a H+ H + activity, p and q are empirical constants, R is the gas constant, n1, n2, m1, m2, n and m are relative to H + Empirical constant of the dissolution-precipitation mechanism, a K+ K + activity;

[0017] The dissolution rate of each original mineral component in each substance reaction is summarized to obtain the total dissolution rate of each original mineral component, and the precipitation rate of each secondary mineral component in each substance reaction is summarized to obtain the total precipitation rate of each secondary mineral component;

[0018] The dissolution amount of each original mineral component in the target area is obtained based on the total dissolution rate and physical property parameters of each original mineral component; the precipitation amount of each secondary mineral component in the target area is obtained based on the total precipitation rate and physical property parameters of each secondary mineral component;

[0019] The predicted rock porosity in the target area is obtained based on the rock porosity, the dissolution amount of each original mineral component and the precipitation amount of each secondary mineral component; the predicted rock permeability in the target area is obtained based on the predicted rock porosity.

[0020] Alternatively, the activity coefficient expression for the solute component is:

[0021]

[0022] Among them, γ i is the activity coefficient of the i-th solute component, z i is the charge of the i-th solute component, I is the ionic strength of the formation water, A is the first constant, B is the second constant, is the third constant, A, B and Related to temperature, is the ionic radius of the i-th solute component;

[0023] The activity expression of the solute component is:

[0024] a i =γ i ×H i ;

[0025] Among them, a i is the activity of the i-th solute component, H i is the concentration of the i-th solute component.

[0026] Alternatively, the fugacity coefficient of the system is expressed as:

[0027]

[0028] Among them, B is the fugacity coefficient, y x is the mole fraction of the xth free gas component, y j is the mole fraction of the jth free gas component, B xj is the second virial cross coefficient, n is the total number of free gas components;

[0029] The fugacity expression of the free gas component is:

[0030] f x =B×P x ;

[0031] Among them, f x is the fugacity of the xth free gas component, P x is the partial pressure of the xth free gas component.

[0032] Optionally, the material reaction model expression is:

[0033]

[0034] Among them, A y is the yth secondary mineral component, r is the total number of secondary mineral components, A w is formation water, A i is the i-th solute component participating in the reaction, A k is the kth original mineral component involved in the reaction, A x is the xth free gas component participating in the reaction, v y is the number of moles of the yth secondary mineral component, v w is the number of moles of formation water involved in the reaction, v i is the number of moles of the i-th solute component participating in the reaction, v k is the number of moles of the kth original mineral component participating in the reaction, v x is the number of moles of the xth free gas component participating in the reaction.

[0035] Alternatively, the activity product of the species reaction can be expressed as:

[0036]

[0037] Among them, Q is the activity product of the substance reaction, v w is the number of moles of formation water involved in the reaction, v i is the number of moles of the i-th solute component participating in the reaction, v k is the number of moles of the kth original mineral component participating in the reaction, v x is the number of moles of the xth free gas component participating in the reaction, a w is the activity of formation water, a i is the activity of the i-th solute component, a k is the activity of the kth original mineral component, a y is the activity of the yth secondary mineral component, f x is the fugacity of the xth free gas component.

[0038] Alternatively, the amount of dissolution of the original mineral composition can be expressed as:

[0039]

[0040] Among them, M k is the dissolution amount of the kth original mineral component, is the volume fraction of the kth original mineral component, C k is the molar mass of the kth original mineral component, is the molar volume of the kth original mineral component, is the total dissolution rate of the kth original mineral component.

[0041] Alternatively, the precipitation amount of the secondary mineral component is expressed as:

[0042]

[0043] Among them, M y is the precipitation amount of the yth secondary mineral component, is the volume fraction of the yth secondary mineral component, C y is the molar mass of the yth secondary mineral component, is the molar volume of the yth secondary mineral component, is the total precipitation rate of the yth secondary mineral formation.

[0044] Alternatively, the rock porosity prediction expression is:

[0045]

[0046] in, Predicting porosity for rocks, is the rock porosity, M k is the dissolution amount of the kth original mineral component, M y is the precipitation amount of the yth secondary mineral component.

[0047] Optionally, the expression is:

[0048]

[0049] Among them, p 预 Predict permeability for rocks.

[0050] The effects of the present invention are as follows:

[0051] The numerical simulation method of water-rock reaction in sandstone reservoirs in potassium-rich fluid environments takes into account the diagenetic minerals and real formation water components developed in real sandstone samples, and uses chemical thermodynamics and kinetics to constrain the dissolution and precipitation processes of minerals. + Under the fluid environment, special constraints are placed on the precipitation of characteristic secondary minerals illite and potassium feldspar; the water-rock reaction of sandstone reservoirs under potassium-rich fluid environment can be accurately numerically simulated to obtain accurate rock predicted porosity and rock predicted permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a flow chart of the numerical simulation method for water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to the present invention;

[0053] Figure 2 It is a schematic diagram of the evolution of the sandstone diagenetic path simulated by the present invention. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0055] Figure 1 This is a flow chart of the numerical simulation method for water-rock reaction in sandstone reservoirs in potassium-rich fluid environments. Figure 1 As shown, the present invention provides a numerical simulation method for water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment, which includes:

[0056] S1, obtain the rock porosity and original mineral components of the target area, as well as the physical properties, specific surface area and equilibrium constant of each original mineral component.

[0057] S2, obtaining solute parameters of each solute component in the formation water in the target area, obtaining activity coefficients of each solute component according to each solute parameter; and obtaining activities of each solute component according to the activity coefficients of each solute component.

[0058] Preferably, the activity coefficient expression of the solute component is:

[0059]

[0060] Among them, γ i is the activity coefficient of the i-th solute component, z i is the charge of the i-th solute component, I is the ionic strength of the formation water, A is the first constant, B is the second constant, is the third constant, A, B and Related to temperature, is the ionic radius of the i-th solute component;

[0061] The activity expression of the solute component is:

[0062] a i =γ i ×H i ;

[0063] Among them, a i is the activity of the i-th solute component, H i is the concentration of the i solute component.

[0064] S3. Obtain free gas parameters of each free gas component in the system, obtain the fugacity coefficient of the system based on the free gas parameters, use the system fugacity coefficient as the fugacity coefficient of each free gas component, and obtain the fugacity of each free gas component based on the fugacity coefficient of each free gas component. The system is composed of formation water, rock, and rock pores in the target area.

[0065] The expression of the system's fugacity coefficient is:

[0066]

[0067] Among them, B is the fugacity coefficient, y x is the mole fraction of the xth free gas component, y j is the mole fraction of the jth free gas component, B xj is the second virial cross coefficient, n is the total number of free gas components;

[0068] The fugacity expression of the free gas component is:

[0069] f x =B×P x ;

[0070] Among them, f x is the fugacity of the xth free gas component, P x is the partial pressure of x free gas components.

[0071] S4, determining the secondary mineral components contained in the target area as well as the physical properties, specific surface area and equilibrium constants of each secondary mineral component, constructing several material reaction models; and determining the activity product of each material reaction based on each material reaction model.

[0072] Preferably, the specific surface area of each original mineral component and the specific surface area of each secondary mineral component are obtained by a specific surface area detection method or the like.

[0073] The thermodynamic database for mineral and solute components in the numerical simulations uses a combination of the LLNL and Minteq databases. The thermodynamic data for organic acids, such as acetic acid, were extracted from the Minteq database and copied into the LLNL database. The temperature range of the organic acid thermodynamic data in the Minteq database is only 0°C to 100°C. Therefore, after copying the organic acid thermodynamic data from the Minteq database into the LLNL database, the existing data needed to be temperature-extended to facilitate application in numerical simulations at temperatures above 100°C. This temperature expansion was calculated using a polynomial expansion method:

[0074] logK=a0+a1T+a2T 2 +a3T 3 +a4T 4 ;

[0075] Where K represents the equilibrium constant, T represents the temperature, and a0, a1, a2, a3, and a4 are constants.

[0076] The common mineral compositions and thermodynamic parameters of sandstones are generally available in the LLNL database. However, it should be noted that some mineral compositions have multiple chemical formulas. For example, plagioclase feldspar has a chemical formula that can be roughly estimated based on other conditions (such as provenance) without detailed determination of its composition. The chemical formula of illite can be obtained from muscovite (KAl3Si3O 10 (OH)2) substitution; dolomite can be reconstructed using calcite and siderite as diterminal components.

[0077] The material reaction model expression is:

[0078]

[0079] Among them, A y is the yth secondary mineral component, r is the total number of secondary mineral components, A w is formation water, A i is the i-th solute component participating in the reaction, A k is the kth original mineral component involved in the reaction, A x is the xth free gas component participating in the reaction, v yis the number of moles of the yth secondary mineral component, v w is the number of moles of formation water involved in the reaction, v i is the number of moles of the i-th solute component participating in the reaction, v k is the number of moles of the kth original mineral component participating in the reaction, v x is the number of moles of the xth free gas component participating in the reaction.

[0080] The activity product expression of substance reaction is:

[0081]

[0082] Among them, Q is the activity product of the substance reaction, a w is the activity of formation water, a i is the activity of the i-th solute component, a k is the activity of the kth original mineral component, a y is the activity of the yth secondary mineral component, f x is the fugacity of the xth free gas component.

[0083] When the mineral is in equilibrium, Q1 is called the equilibrium constant K of the mineral, and the saturation index of the mineral is:

[0084]

[0085] Among them, SI is the saturation index, K u is the equilibrium constant of the u-th original mineral component or the u-th secondary mineral component.

[0086] SI determines the dissolution or precipitation behavior of a mineral. When SI>1, the mineral dissolves, and when SI<1, the mineral precipitates.

[0087] In the present invention, the calculation method of the mathematical iteration of the material reaction refers to Newton's method:

[0088]

[0089] Where f represents the random function of the differential method, x represents the base number, U represents the residual, and v represents the vth iteration. The constraint formula for the dissolution and precipitation kinetics of minerals is based on the transition state theory:

[0090]

[0091] in Indicates the rate of mineral dissolution or precipitation, A S is the mineral surface area, k + is the reaction rate constant, f(a i ) is the function of the activity of the i-th solute component, g(ΔG r) is a function of the mineral saturation index.

[0092] S5, based on the activity product of each substance reaction, the specific surface area of each original mineral component and the equilibrium constant, the dissolution rate of each original mineral component in each substance reaction is obtained; based on the activity product of each substance reaction, the specific surface area of each secondary mineral component and the equilibrium constant, the precipitation rate of each secondary mineral component in each substance reaction is obtained.

[0093] When the original mineral component or the secondary mineral component is potassium feldspar, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is:

[0094]

[0095] Thus introducing too high dissolved K + The inhibitory effect of activity on the dissolution rate of potassium feldspar.

[0096] When the original mineral component or the secondary mineral component is non-potassium feldspar, such as quartz, feldspar, calcite or kaolinite, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is:

[0097]

[0098] in, is the dissolution rate of the uth original mineral component or the precipitation rate of the uth secondary mineral component, SA u is the specific surface area of the u-th original mineral component or the u-th secondary mineral component, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under acidic conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under neutral conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under alkaline conditions, E acid is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under acidic conditions, E neutral is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under neutral conditions, E base is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under alkaline conditions, T is the temperature value, Q is the activity product of the material reaction, K u is the equilibrium constant of the uth original mineral component or the uth secondary mineral component, a H+ H + activity, p and q are empirical constants, R is the gas constant, n1, n2, m1, m2, n and m are relative to H+ Empirical constant of the dissolution-precipitation mechanism, a K+ K + activity.

[0099] Under conditions exceeding 120°C, montmorillonite can be converted into illite in large quantities. The kinetic constraints of montmorillonite illitization can be based on the following formula:

[0100]

[0101] Where S represents the percentage of montmorillonite layer in montmorillonite-illite mixed layer mineral, t is time (seconds), and A is the rate constant, which is 8.08×10 -4 s -1 , Ea represents activation energy, [K + ] indicates K dissolved in water + The molar concentration of .

[0102] The transformation of montmorillonite to illite can be divided into two significantly different stages according to its different mechanisms. The first stage is that montmorillonite is transformed into illite through the mechanism of solid-state transformation. The notable feature of this stage is that the illite formed inherits the crystal morphology of montmorillonite. This stage generally occurs under relatively low temperatures, and its activation energy is 69.7 kJ / mol. The second stage involves the dissolution of montmorillonite and the precipitation of illite. This process is a dissolution-reprecipitation mechanism, which usually occurs at higher temperatures and has an activation energy of 37.4 kJ / mol. Depending on the burial temperature of the sandstone, one of the two activation energy values can be used for comparison.

[0103] S6, summing up the dissolution rate of each original mineral component in each material reaction to obtain the total dissolution rate of each original mineral component, and summing up the precipitation rate of each secondary mineral component in each material reaction to obtain the total precipitation rate of each secondary mineral component.

[0104] S7, obtaining the dissolution amount of each original mineral component in the target area based on the total dissolution rate and physical property parameters of each original mineral component; obtaining the precipitation amount of each secondary mineral component in the target area based on the total precipitation rate and physical property parameters of each secondary mineral component.

[0105] The expression for the dissolution amount of the original mineral components is:

[0106]

[0107] Among them, M k is the dissolution amount of the kth original mineral component, is the volume fraction of the kth original mineral component, C k is the molar mass of the kth original mineral component, is the molar volume of the kth original mineral component, is the total dissolution rate of the kth original mineral component.

[0108] The precipitation amount of secondary mineral components is expressed as:

[0109]

[0110] Among them, M y is the precipitation amount of the yth secondary mineral component, is the volume fraction of the yth secondary mineral component, C y is the molar mass of the yth secondary mineral component, is the molar volume of the yth secondary mineral component, is the total precipitation rate of the yth secondary mineral formation.

[0111] S8. Based on the rock porosity, the dissolution amount of each original mineral component, and the precipitation amount of each secondary mineral component, the predicted rock porosity in the target area is obtained; based on the predicted rock porosity, the predicted rock permeability in the target area is obtained.

[0112] The rock porosity prediction expression is:

[0113]

[0114] in, Predicting porosity for rocks, is the rock porosity, M k is the dissolution amount of the kth original mineral component, M y is the precipitation amount of the yth secondary mineral component.

[0115] The rock permeability prediction expression is:

[0116]

[0117] Among them, p 预 Predict permeability for rocks.

[0118] The numerical simulation involves two water components, namely the water in the initial system and the influent water. The initial water can be obtained in two ways: one is to measure the solute composition of real formation water samples by experimental means, and the other is to obtain it by running a reaction path simulation;

[0119] The determination of actual formation water composition requires caution. The pH value needs to be measured immediately after the water sample is obtained during drilling. After the water sample is returned to the laboratory, the organic acid content must be determined at the same time as other components.

[0120] The method for obtaining the initial water composition through reaction path simulation is as follows: first, select representative sandstone mineral components and measure or estimate the content and specific surface area of each mineral. Then, use a 1M NaCl initial aqueous solution to react with the mineral components. The dissolution and precipitation rates of each mineral are constrained by the aforementioned formula. The reaction time is set to 1 year. The solution components after the reaction should be in chemical equilibrium with all primary and secondary minerals present in the reaction (i.e., log(Q / K) = 0). In addition, it should be noted that the pH of the solution after the reaction should not significantly exceed the pH range of the actual formation water at the temperature of the sandstone sample.

[0121] Based on the initial water composition, the composition of the influent water can be established, generally by introducing a certain amount of organic acid or CO2 as the active component to trigger the chemical reaction.

[0122] The concentration of the introduced organic acid should refer to the concentration range of organic acid in the actual formation water in the area under the temperature conditions.

[0123] The partial pressure of the introduced CO2 should also refer to the range of CO2 partial pressure in the actual formation water in the region under the temperature conditions.

[0124] The selection of secondary minerals should refer to the secondary minerals that appear in real sandstone samples. Secondary minerals that do not appear in the sample should generally not be introduced into the numerical simulation to participate in the reaction. In particular, it should be noted that K-rich + The fluid environment should allow the precipitation of secondary illite and potassium feldspar.

[0125] like Figure 2 As shown in the figure, a set of simulations using the above numerical simulation method are shown. + Schematic diagram of the diagenetic evolution path of sandstone under low K concentration conditions. The original mineral components include albite and quartz, and the secondary mineral components include kaolinite, quartz and potassium feldspar. + When the concentration is 2.5, sodium feldspar dissolution occurs accompanied by the precipitation of kaolinite, quartz and potassium feldspar, but when K + When the concentration increased to 100 mg / L, only the precipitation of secondary potassium feldspar occurred. Figure 2 In the figure, positive values on the vertical axis indicate mineral dissolution, and negative values indicate mineral precipitation.

[0126] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A numerical simulation method for water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment, characterized in that: It includes: Obtain the rock porosity and original mineral components of the target area, as well as the physical properties, specific surface area and equilibrium constants of each original mineral component; Obtaining the solute parameters of each solute component in the formation water of the target area, obtaining the activity coefficient of each solute component based on the solute parameters; obtaining the activity of each solute component based on the activity coefficient of each solute component; Obtaining free gas parameters of each free gas component in the system, obtaining the fugacity coefficient of the system based on each free gas parameter, using the fugacity coefficient of the system as the fugacity coefficient of each free gas component, and obtaining the fugacity of each free gas component based on the fugacity coefficient of each free gas component; the system is composed of formation water, rock, and rock pores in the target area; Determine the secondary mineral components contained in the target area and the physical properties, specific surface area and equilibrium constant of each secondary mineral component, and construct several material reaction models; determine the activity product of each material reaction based on each material reaction model; The dissolution rate of each original mineral component in each substance reaction is obtained based on the activity product of each substance reaction, the specific surface area of each original mineral component and the equilibrium constant. The precipitation rate of each secondary mineral component in each substance reaction is obtained based on the activity product of each substance reaction, the specific surface area of each secondary mineral component and the equilibrium constant. When the original mineral component or the secondary mineral component is potassium feldspar, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is: When the original mineral component or the secondary mineral component is non-potassium feldspar, the expression for the dissolution rate of the original mineral component or the precipitation rate of the secondary mineral component in the material reaction is: in, is the dissolution rate of the uth original mineral component or the precipitation rate of the uth secondary mineral component, SA u is the specific surface area of the u-th original mineral component or the u-th secondary mineral component, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under acidic conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under neutral conditions, is the dissolution rate of the uth original mineral component or the rate constant of the uth secondary mineral component under alkaline conditions, E acid is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under acidic conditions, E neutral is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under neutral conditions, E base is the dissolution rate of the uth original mineral component or the activation energy of the uth secondary mineral component under alkaline conditions, T is the temperature value, Q is the activity product of the material reaction, K u is the equilibrium constant of the u-th original mineral component or the u-th secondary mineral component, H + activity, p and q are empirical constants, R is the gas constant, n1, n2, m1, m2, n and m are relative to H + Empirical constants of the dissolution-precipitation mechanism, K + activity; The dissolution rate of each original mineral component in each substance reaction is summarized to obtain the total dissolution rate of each original mineral component, and the precipitation rate of each secondary mineral component in each substance reaction is summarized to obtain the total precipitation rate of each secondary mineral component; The dissolution amount of each original mineral component in the target area is obtained based on the total dissolution rate and physical property parameters of each original mineral component; the precipitation amount of each secondary mineral component in the target area is obtained based on the total precipitation rate and physical property parameters of each secondary mineral component; The predicted rock porosity in the target area is obtained based on the rock porosity, the dissolution amount of each original mineral component and the precipitation amount of each secondary mineral component; the predicted rock permeability in the target area is obtained based on the predicted rock porosity.

2. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The activity coefficient expression of the solute component is: Among them, γ i is the activity coefficient of the i-th solute component, z i is the charge of the i-th solute component, I is the ionic strength of the formation water, A is the first constant, B is the second constant, is the third constant, A, B and Related to temperature, is the ionic radius of the i-th solute component. The activity expression of the solute component is: a i =c i ×H i ; Among them, a i is the activity of the i-th solute component, H i is the concentration of the i-th solute component.

3. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The expression of the system's fugacity coefficient is: Among them, B is the fugacity coefficient, y x is the mole fraction of the xth free gas component, y j is the mole fraction of the jth free gas component, B xj is the second virial cross coefficient, and n is the total number of free gas components. The fugacity expression of the free gas component is: f x =B×P x ; Among them, f x is the fugacity of the xth free gas component, P x is the partial pressure of the xth free gas component.

4. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The material reaction model expression is: Among them, A y is the yth secondary mineral component, r is the total number of secondary mineral components, A w is formation water, A i is the i-th solute component participating in the reaction, A k is the kth original mineral component involved in the reaction, A x is the xth free gas component participating in the reaction, v y is the number of moles of the yth secondary mineral component, v w is the number of moles of formation water involved in the reaction, v i is the number of moles of the i-th solute component participating in the reaction, v k is the number of moles of the kth original mineral component participating in the reaction, v x is the number of moles of the xth free gas component participating in the reaction.

5. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The activity product expression of substance reaction is: Among them, Q is the activity product of the substance reaction, v w is the number of moles of formation water involved in the reaction, v i is the number of moles of the i-th solute component participating in the reaction, v k is the number of moles of the kth original mineral component participating in the reaction, v x is the number of moles of the xth free gas component participating in the reaction, a w is the activity of formation water, a i is the activity of the i-th solute component, a k is the activity of the kth original mineral component, a y is the activity of the yth secondary mineral component, f x is the fugacity of the xth free gas component.

6. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The expression for the dissolution amount of the original mineral components is: Among them, M k is the dissolution amount of the kth original mineral component, is the volume fraction of the kth original mineral component, C k is the molar mass of the kth original mineral component, is the molar volume of the kth original mineral component, is the total dissolution rate of the kth original mineral component.

7. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The precipitation amount of secondary mineral components is expressed as: Among them, M y is the precipitation amount of the yth secondary mineral component, is the volume fraction of the yth secondary mineral component, C y is the molar mass of the yth secondary mineral component, is the molar volume of the yth secondary mineral component, is the total precipitation rate of the yth secondary mineral formation.

8. The method for numerical simulation of water-rock reaction in sandstone reservoirs in a potassium-rich fluid environment according to claim 1, characterized in that: The rock porosity prediction expression is: in, Predicting porosity for rocks, is the rock porosity, M k is the dissolution amount of the kth original mineral component, M y is the precipitation amount of the yth secondary mineral component.

9. The method for numerical simulation of water-rock reaction in sandstone reservoirs in potassium-rich fluid environments according to claim 8, wherein the expression for: Among them, p 预 Predict permeability for rocks.

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