A method and system for numerical simulation of fluid-solid coupling of carbonate rock acid-rock reaction

Abstract

The present invention relates to a method and system for numerical simulation of fluid-solid coupling of carbonate rock acid-rock reaction, and relates to the field of numerical simulation of oil reservoirs. First, a core sample corresponding to carbonate rock is CT scanned to obtain a CT scan image; a pore network model is constructed according to the CT scan image; secondly, the actual diameter and fluid model corresponding to each pore channel are determined based on the pore network model; the actual diameter corresponding to each pore channel is the diameter corresponding to each pore channel that simultaneously considers dissolution and stress; then the porosity is calculated based on the actual diameter corresponding to each pore channel; finally, the permeability of the pore network model is calculated based on the fluid model corresponding to each pore channel. The present invention not only considers the change of pore structure caused by chemical dissolution, but also considers the change of pore structure caused by mechanical compaction due to high stress during acidification. Therefore, the diameter and permeability corresponding to each pore channel calculated based on the pore network model are more accurate, and the acidification process can be simulated more accurately.

Description

Technical Field

[0001] The invention relates to the field of numerical simulation of oil reservoirs, and in particular to a method and system for numerical simulation of fluid-solid coupling of carbonate rock-acid rock reaction. Background Art

[0002] With the continuous development of human society, energy consumption is becoming more and more rapid. Global energy consumption is still dominated by fossil energy. As of the end of 2019, oil and gas resources accounted for about 57.3% of global energy consumption. Carbonate oil and gas reservoirs are widely distributed and have large reserves. They are one of the most important oil and gas exploration and development areas in the world, accounting for 52% of the world's proven oil reserves and 60% of the world's total oil and gas production. China's western carbonate oil and gas resources are very rich, with the characteristics of old geological age and deep burial. They belong to deep oil and gas reservoirs. Their reservoir space types are diverse, heterogeneous, complex flow laws, poor development effects and low recovery rates. Acidizing is one of the important transformation technologies for carbonate reservoirs. Acid is injected into the formation through the wellbore to react and dissolve with carbonate rocks. The acid erodes the rock to form a high-conductivity channel and removes the pollution zone near the wellbore area, improving the permeability of the formation near the wellbore, which helps to improve the recovery rate of such reservoirs.

[0003] At present, there are four numerical simulation models used in the numerical simulation of acid-rock reaction during the acidizing process of carbonate reservoirs: capillary model, fractal model, pore network model and continuous model. The capillary model assumes the wormhole as a simple cylindrical capillary and simulates the axial and radial flow of acid in the wormhole. This model describes the formation and mutual influence of wormholes in carbonate formations during acid etching. It can simply calculate the growth of wormholes in the axial and radial directions, but cannot calculate the optimal injection rate of acid and the minimum pore breakthrough volume. In addition, this model is only applicable to the case where the reaction is controlled by mass transfer, and cannot describe the case affected by the reaction rate. The fractal model assumes that the dissolution reaction of the rock is similar to the dissolution reaction of a single capillary and is proposed considering the fractal properties of a single wormhole. The fractal model is a continuous model used to simulate the reaction flow problem in porous media seepage. However, this model cannot calculate the minimum amount of acid. In addition, since the model contains too many unknown parameters, it cannot be used to study the formation process of wormholes. The pore network model replaces each pore space in the spherical particle filling model with a uniform circular pipe column to obtain a three-dimensional pipe network. The diameters of different pipes in the network are characterized by random numbers to perform accurate flow calculations. The model has good results in experimental and field fitting, but the large amount of computing time required is the main reason restricting its promotion. The dual-scale continuity model divides the scale of the core into Darcy scale (between μm and cm) and pore scale (μm). The Darcy scale model mainly describes factors such as acid flow, reaction, mass transfer and diffusion; the pore scale model mainly describes the changes in core porosity, permeability and reaction contact area. The two-scale models are coupled together, taking into account the convective mass transfer and chemical reactions in the pores, and can approximately simulate the experimental results. Although the model comprehensively considers the wormhole growth conditions (affected by mass transfer or reaction rate), changes in acid concentration, changes in formation porosity and minimum pore breakthrough volume, it is worth noting that the simulation accuracy of the acidizing process by the dual-scale model is greatly restricted by the limitations of the basic assumptions of the model establishment, that is, the dual-scale continuity model still requires a large number of auxiliary equations to improve the accuracy of the model.

[0004] In summary, the existing numerical simulation models and technologies can only consider the changes in pore structure caused by chemical dissolution, but do not consider the changes in pore structure caused by high-stress mechanical compaction during the acidizing process. Therefore, the above models cannot accurately simulate the acidizing process, and there are still certain limitations in the application of numerical simulation of deep carbonate acidizing process. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for fluid-solid coupling numerical simulation of carbonate rock acid-rock reaction, so as to accurately simulate the acidification process.

[0006] To achieve the above object, the present invention provides a method for fluid-solid coupling numerical simulation of carbonate rock acid-rock reaction, the method comprising:

[0007] Perform CT scanning on the core samples corresponding to the carbonate rock to obtain CT scanning images;

[0008] constructing a pore network model according to the CT scan image;

[0009] Determine the actual diameter and fluid model corresponding to each pore channel based on the pore network model; the actual diameter corresponding to each pore channel is the diameter corresponding to each pore channel taking into account both dissolution and stress effects;

[0010] The porosity is calculated based on the actual diameter corresponding to each pore;

[0011] The permeability of the pore network model is calculated based on the fluid model corresponding to each pore channel.

[0012] Optionally, constructing a pore network model according to the CT scan image specifically includes:

[0013] Extracting sample parameter distribution on the CT scan image using a watershed segmentation algorithm;

[0014] Constructing an equivalent network with a pore topological relationship according to the sample parameter distribution;

[0015] The equivalent network is processed to obtain a pore network model.

[0016] Optionally, determining the actual diameter and fluid model corresponding to each pore channel based on the pore network model specifically includes:

[0017] Determine a fluid model corresponding to each pore in the pore network model; the fluid model is an equivalent model of fluid flowing through each pore in the pore network model;

[0018] Calculate the first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is the diameter change caused by chemical dissolution;

[0019] Calculate the second diameter change corresponding to each hole; the second diameter change is the diameter change corresponding to each hole caused by stress;

[0020] Calculating a total diameter change amount according to the first diameter change amount and the second diameter change amount, wherein the total diameter change amount is a diameter change amount that takes both dissolution and stress into consideration;

[0021] The actual diameter corresponding to each channel is calculated based on the initial diameter corresponding to each channel and the total amount of diameter change.

[0022] Optionally, the calculating the second diameter variation corresponding to each channel specifically includes:

[0023] Calculate the total effective stiffness of the pore network model in each direction;

[0024] calculating a macroscopic boundary displacement based on the total effective stiffness;

[0025] Calculating the radial strain of each pore according to the macro boundary displacement;

[0026] The second diameter variation is calculated according to the radial strain of each hole.

[0027] Optionally, a specific formula for calculating the first diameter change corresponding to each channel is:

[0028]

[0029]

[0030] in, represents the first diameter change of the pore ij caused by chemical dissolution, Δt represents the reaction time, represents the initial acid concentration at node i, A ij represents the reaction surface area, d ij represents the diameter of the hole ij, q ij represents the volume flow rate in the pore ij, c sol represents the concentration of soluble substances on the pore wall, v represents the reaction order of the chemical reaction, represents the effective reaction rate coefficient, λ represents the surface reaction rate, D represents the molecular diffusion coefficient, and Sh represents the Sherwood number.

[0031] The present invention also provides a carbonate rock acid rock reaction fluid-solid coupling numerical simulation system, the system comprising:

[0032] A CT scanning module is used to perform CT scanning on the core samples corresponding to the carbonate rock to obtain a CT scanning image;

[0033] A pore network model building module, used to build a pore network model according to the CT scan image;

[0034] A parameter determination module, used to determine the actual diameter corresponding to each pore channel and the fluid model based on the pore network model; the actual diameter corresponding to each pore channel is the diameter corresponding to each pore channel taking into account both dissolution and stress effects;

[0035] A porosity calculation module, used to calculate the porosity based on the actual diameter corresponding to each pore;

[0036] The permeability calculation module is used to calculate the permeability of the pore network model based on the fluid model corresponding to each pore channel.

[0037] Optionally, the pore network model construction module specifically includes:

[0038] An extraction unit, used for extracting sample parameter distribution on the CT scan image by using a watershed segmentation algorithm;

[0039] An equivalent network determination unit, used to construct an equivalent network with a pore topological relationship according to the sample parameter distribution;

[0040] The pore network model determination unit is used to process the equivalent network to obtain a pore network model.

[0041] Optionally, the parameter determination module specifically includes:

[0042] A fluid model determination unit, used to determine the fluid model corresponding to each pore in the pore network model; the fluid model is an equivalent model of fluid flowing through each pore in the pore network model;

[0043] A first diameter change calculation unit is used to calculate a first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is a diameter change caused by chemical dissolution;

[0044] A second diameter variation calculation unit is used to calculate a second diameter variation corresponding to each hole; the second diameter variation is a diameter variation corresponding to each hole caused by stress;

[0045] a diameter change total amount calculation unit, used to calculate the diameter change total amount according to the first diameter change amount and the second diameter change amount, wherein the diameter change total amount is the diameter change amount that takes both dissolution and stress into consideration;

[0046] The actual diameter calculation unit is used to calculate the actual diameter corresponding to each channel according to the initial diameter corresponding to each channel and the total amount of diameter change.

[0047] Optionally, the second diameter change calculation unit includes:

[0048] Total effective stiffness calculation subunit, used to calculate the total effective stiffness of the pore network model in each direction;

[0049] A macro boundary displacement calculation subunit, used for calculating the macro boundary displacement according to the total effective stiffness;

[0050] A radial strain calculation subunit, used for calculating the radial strain of each channel according to the macro boundary displacement;

[0051] The second diameter variation calculation subunit is used to calculate the second diameter variation according to the radial strain of each hole.

[0052] Optionally, a specific formula for calculating the first diameter change corresponding to each channel is:

[0053]

[0054]

[0055] in, represents the first diameter change of the pore ij caused by chemical dissolution, Δt represents the reaction time, represents the initial acid concentration at node i, A ij represents the reaction surface area, d ij represents the diameter of the hole ij, q ij represents the volume flow rate in the pore ij, c sol represents the concentration of soluble substances on the pore wall, v represents the reaction order of the chemical reaction, represents the effective reaction rate coefficient, λ represents the surface reaction rate, D represents the molecular diffusion coefficient, and Sh represents the Sherwood number.

[0056] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0057] The present invention not only considers the changes in pore structure caused by chemical dissolution, but also considers the changes in pore structure caused by mechanical compaction due to high stress during the acidification process. Therefore, the diameter and permeability corresponding to each pore channel calculated based on the pore network model are more accurate, and the acidification process can be simulated more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, 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 labor.

[0059] Figure 1 This is a flow chart of the fluid-solid coupling numerical simulation method for carbonate rock-acid rock reaction of the present invention;

[0060] Figure 2 A schematic diagram of the pore network model of the present invention is established;

[0061] Figure 3 This is a structural diagram of the carbonate rock-acid rock reaction fluid-solid coupling numerical simulation system of the present invention. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, 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.

[0063] The purpose of the present invention is to provide a method and system for fluid-solid coupling numerical simulation of carbonate rock acid-rock reaction, so as to realize accurate simulation of acidification process.

[0064] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1

[0066] like Figure 1 As shown, the present invention discloses a method for fluid-solid coupling numerical simulation of carbonate rock acid-rock reaction, the method comprising:

[0067] Step S1: Perform CT scanning on the core sample corresponding to the carbonate rock to obtain a CT scanning image.

[0068] Step S2: constructing a pore network model based on the CT scan image.

[0069] Step S3: determining the actual diameter corresponding to each pore and the fluid model based on the pore network model; the actual diameter corresponding to each pore is the diameter corresponding to each pore taking into account both dissolution and stress effects.

[0070] Step S4: Calculate the porosity based on the actual diameter corresponding to each pore.

[0071] Step S5: Calculate the permeability of the pore network model based on the fluid model corresponding to each pore channel.

[0072] The following is a detailed discussion of each step:

[0073] Step S2: constructing a pore network model according to the CT scan image, specifically comprising:

[0074] Step S21: extracting sample parameter distribution on the CT scan image using a watershed segmentation algorithm; the sample parameter distribution includes: solid distribution, pore distribution, and distribution of cracks and holes.

[0075] Step S22: constructing an equivalent network with pore topological relationship according to the sample parameter distribution.

[0076] Step S23: Processing the equivalent network to obtain a pore network model; the parameters of the pore network model of the present invention, the parameters of the pore network model include: the number of pores N β , number of channels s, channel length l ij , hole diameter d ij , the concentration of soluble substances on the pore wall c sol , initial solid volume

[0077] In this embodiment, the equivalent network is processed to obtain a pore network model; specifically, the processing mentioned in the present invention refers to directly converting the irregular equivalent network into a regular pore network model as shown in (b) of Figure (2), only changing the shape, while the diameter of each pore, the concentration of soluble substances on the wall and other properties remain unchanged. In addition, the CT scan image is as follows Figure 2 As shown in Figure (a), the established pore network model is as follows Figure 2 As shown in Figure (b), the schematic diagram of the pore unit in the pore network model is as follows Figure 2 As shown in Figure (c), the channel unit includes 4 channels, and the channel between node i and node j is referred to as channel ij.

[0078] Step S3: determining the actual diameter and fluid model corresponding to each pore based on the pore network model, specifically comprising:

[0079] Step S31: determining the fluid model corresponding to each pore in the pore network model; the fluid model is: an equivalent model of fluid flowing through each pore in the pore network model.

[0080] The calculation formula of the fluid model is:

[0081]

[0082] Among them, q ij represents the volume flow rate in the pore ij, d ij and l ij Represent the diameter and length of the pore ij, respectively, (P j -P i ) represents the pressure drop along the channel between the connecting node i and the node j, μ represents the viscosity of the fluid, i and j are both positive integers greater than 1, and i is not equal to j.

[0083] The continuity conditions at each node are:

[0084] ∑q ij =0 (2).

[0085] By assigning an initial value P0 to the pressure at the inlet of the pore network model, the sparse matrix composed of formulas (1) and (2) is used to solve the pressure P at each nodei and the volume flow rate q in each channel ij .

[0086] Step S32: Calculate the first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is the diameter change caused by chemical dissolution.

[0087] The specific formula for the first diameter change corresponding to each channel is:

[0088]

[0089]

[0090]

[0091] in, represents the first diameter change of the pore ij caused by chemical dissolution, Δt represents the reaction time, represents the initial acid concentration at node i, c ij represents the acid concentration in the pore ij, A ij A is the reaction surface area. ij =2πd ij l ij , d ij and l ij Respectively represent the diameter and length of the channel ij, q ij represents the volume flow rate in the pore ij, c sol represents the concentration of soluble substances on the pore wall, v represents the reaction order of the chemical reaction, which is equal to 1 here. represents the effective reaction rate coefficient, λ represents the surface reaction rate, which is usually a given constant, D represents the molecular diffusion coefficient, which is usually a given constant, and Sh represents the Sherwood number, which is generally taken as 4.

[0092] Step S33: Calculating the second diameter variation corresponding to each channel, specifically including:

[0093] Step S331: Calculate the total effective stiffness of the pore network model in each direction. The specific formula is:

[0094]

[0095]

[0096]

[0097] in, represents the total effective stiffness of the pore network model in the β direction, N βrepresents the number of pores in the pore network model in the β direction, s represents the number of rows in the pore network model, and s β represents the number of rows of the pore network model in the β direction, k s Indicated by N s The stiffness of the sth row of channel units, κ I represents the effective stiffness of the channel unit I, κ s represents the solid bulk modulus of the sth row in the pore network model, κ s =E / 3(1-2υ),κ φ represents the pore stiffness, κ φ =Eπd ij 2 / 4, υ represents Poisson's ratio, E represents Young's modulus, d ij represents the diameter of the hole ij, φ I Represents the local porosity of pore unit I.

[0098] In this embodiment, the sum of formula (6) refers to the sum of all cell rows (N) arranged along the β direction. β The sum of Figure 2 As can be seen from Figure (c), the channel unit includes 4 channels.

[0099] Step S332: Calculate the macro boundary displacement according to the total effective stiffness. The specific calculation formula is:

[0100]

[0101] in, represents the macro boundary displacement caused by the macro external stress, σ represents the macro external stress applied on the boundary wall, Represents the total effective stiffness of the pore network model in each direction.

[0102] Step S333: Calculate the radial strain of each channel according to the macro boundary displacement. The specific calculation formula is:

[0103]

[0104] Among them, ∈ ij represents the radial strain of the hole ij, κ φ represents the pore stiffness, represents the strain in the β direction, σ represents the macroscopic external stress applied on the boundary wall, Represents the total effective stiffness of the pore network model in each direction.

[0105] Macroscopic boundary displacement caused by macroscopic external stress σ The specific formula is:

[0106]

[0107] Where σ represents the macroscopic external stress applied on the boundary wall, Represents the total effective stiffness of the pore network model in each direction.

[0108] The stress in each direction of a cell I in a given row is Equal, that is:

[0109]

[0110]

[0111] in, represents the macro boundary displacement caused by macro external stress, κ s represents the solid bulk modulus of the sth row in the pore network model, represents the stress magnitude of the sth row in the pore network model.

[0112] The radial strain of each hole is:

[0113] ∈ ij =σ ij / κ φ (14);

[0114] in,

[0115] The pore strain is calculated based on linear elasticity and effective medium theory, considering the linear relationship between stress and strain of each pore unit I, then:

[0116]

[0117] in, and denote the stress and strain in the β direction, κ I Represents the effective stiffness of the channel unit I.

[0118] Combining formulas (11)-(15), we can derive formula (10).

[0119] Step S334: Calculate the second diameter variation according to the radial strain of each channel; the second diameter variation is the diameter variation corresponding to each channel caused by the stress.

[0120] The specific formula for calculating the second diameter change is:

[0121]

[0122] in, represents the change in the second diameter of the channel ij caused by stress, R′ij represents the diameter since the beginning of the simulation when only dissolution is considered and compaction is not considered, represents the initial diameter corresponding to the hole ij, ∈ ij Represents the radial strain of channel ij.

[0123] Step S34: Calculate the total diameter change amount that takes both dissolution and stress into consideration based on the first diameter change amount and the second diameter change amount, wherein the total diameter change amount is the diameter change amount that takes both dissolution and stress into consideration.

[0124] The specific calculation formula for calculating the total amount of diameter change is:

[0125]

[0126] in, represents the change in the second diameter of the channel ij caused by stress, represents the first diameter change of the pore ij caused by chemical dissolution, ΔR ij Represents the total diameter change taking into account both dissolution and stress effects.

[0127] Step S35: Calculate the actual diameter corresponding to each channel according to the initial diameter and the total diameter change corresponding to each channel. The specific calculation formula is:

[0128]

[0129] in, represents the initial diameter of the pore ij, ΔR ij represents the total diameter change considering both dissolution and stress, R ij It represents the actual diameter corresponding to each pore, that is, the diameter corresponding to the pore ij taking into account both dissolution and stress.

[0130] Step S4: Calculate the porosity based on the actual diameter corresponding to each pore. The specific calculation formula is:

[0131]

[0132] Where φ represents the porosity, V pore represents the total volume of all pores in the pore network model, V total represents the total volume of the pore network model, l ij Represents the length of the channel ij.

[0133] Step S5: Calculate the permeability of the pore network model based on the fluid model corresponding to each pore channel. The specific calculation formula is:

[0134]

[0135]

[0136] Where k represents the permeability of the pore network model, ν represents the average flow velocity at the inlet of the pore network model, n represents the number of pores in the first row of the pore network model, μ represents the fluid kinematic viscosity, L represents the length of the pore network model along the flow direction, ΔP represents the pressure difference between the inlet and outlet of the pore network model, ΔP = P0-P s , P0 represents the initial injection pressure at the inlet end, P s Indicates the pressure at the outlet, q 1j represents the fluid model corresponding to the first row of pores in the pore network model, d ij Represents the diameter of the hole ij.

[0137] The influence of stress on permeability in the present invention depends largely on the spatial extent of dissolution. The pore network model is used to simulate different dissolution modes and optimal injection rates in the carbonate rock acid-rock reaction process under stress by changing the stress magnitude σ, injection pressure P, injection volume flow rate q and acid concentration c parameters.

[0138] Example 2

[0139] like Figure 3 As shown, a carbonate rock acid-rock reaction fluid-solid coupling numerical simulation system, the system comprising:

[0140] The CT scanning module 301 is used to perform CT scanning on the core sample corresponding to the carbonate rock to obtain a CT scanning image.

[0141] The pore network model building module 302 is used to build a pore network model according to the CT scan image.

[0142] The parameter determination module 303 is used to determine the actual diameter corresponding to each pore and the fluid model based on the pore network model; the actual diameter corresponding to each pore is the diameter corresponding to each pore taking into account both dissolution and stress effects.

[0143] The porosity calculation module 304 is used to calculate the porosity based on the actual diameter corresponding to each pore.

[0144] The permeability calculation module 305 is used to calculate the permeability of the pore network model based on the fluid model corresponding to each pore channel.

[0145] As an optional implementation, the pore network model building module 302 of the present invention specifically includes:

[0146] The extraction unit is used to extract the sample parameter distribution on the CT scan image by using a watershed segmentation algorithm.

[0147] The equivalent network determination unit is used to construct an equivalent network with a pore topological relationship according to the sample parameter distribution.

[0148] The pore network model determination unit is used to process the equivalent network to obtain a pore network model.

[0149] As an optional implementation manner, the parameter determination module 303 of the present invention specifically includes:

[0150] The fluid model determination unit is used to determine the fluid model corresponding to each pore in the pore network model; the fluid model is an equivalent model of the fluid flowing through each pore in the pore network model.

[0151] The first diameter change calculation unit is used to calculate the first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is the diameter change caused by chemical dissolution.

[0152] The second diameter variation calculation unit is used to calculate the second diameter variation corresponding to each channel; the second diameter variation is the diameter variation corresponding to each channel caused by stress.

[0153] A total diameter change calculation unit is used to calculate the total diameter change based on the first diameter change and the second diameter change, wherein the total diameter change is the diameter change that takes dissolution and stress effects into consideration at the same time.

[0154] The actual diameter calculation unit is used to calculate the actual diameter corresponding to each channel according to the initial diameter corresponding to each channel and the total amount of diameter change.

[0155] As an optional implementation, the second diameter change calculation unit of the present invention includes:

[0156] The total effective stiffness calculation subunit is used to calculate the total effective stiffness of the pore network model in each direction.

[0157] The macro boundary displacement calculation subunit is used to calculate the macro boundary displacement according to the total effective stiffness.

[0158] The radial strain calculation subunit is used to calculate the radial strain of each channel according to the macro boundary displacement.

[0159] The second diameter variation calculation subunit is used to calculate the second diameter variation according to the radial strain of each hole.

[0160] The same parts as those in Example 1 will not be described in detail here.

[0161] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0162] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for numerical simulation of fluid-solid coupling of carbonate rock acid-rock reaction, characterized in that: The method comprises: Perform CT scanning on the core samples corresponding to the carbonate rock to obtain CT scanning images; constructing a pore network model according to the CT scan image; Determine the actual diameter and fluid model corresponding to each pore channel based on the pore network model; the actual diameter corresponding to each pore channel is the diameter corresponding to each pore channel taking into account both dissolution and stress effects; The porosity is calculated based on the actual diameter corresponding to each pore; The permeability of the pore network model is calculated based on the fluid model corresponding to each pore channel; The calculation formula of the fluid model is: Among them, q ij represents the volume flow rate in the pore ij, d ij and l ij Represent the diameter and length of the pore ij, respectively, (P j -P i ) represents the pressure drop along the pore between the connecting node i and the node j, μ represents the viscosity of the fluid, i and j are both positive integers greater than 1, and i is not equal to j; The calculation formula of the permeability of the pore network model is: Where k represents the permeability of the pore network model, v represents the average flow velocity at the inlet of the pore network model, n represents the number of pores in the first row of the pore network model, μ represents the fluid kinematic viscosity, L represents the length of the pore network model along the flow direction, ΔP represents the pressure difference between the inlet and outlet of the pore network model, ΔP = P0-P s , P0 represents the initial injection pressure at the inlet end, P s Indicates the pressure at the outlet, q 1j represents the fluid model corresponding to the first row of pores in the pore network model, d ij Represents the diameter of the hole ij.

2. The method for fluid-solid coupling numerical simulation of carbonate rock-acid rock reaction according to claim 1 is characterized in that: The step of constructing a pore network model according to the CT scan image specifically includes: Extracting sample parameter distribution on the CT scan image using a watershed segmentation algorithm; Constructing an equivalent network with a pore topological relationship according to the sample parameter distribution; The equivalent network is processed to obtain a pore network model.

3. The method for fluid-solid coupling numerical simulation of carbonate rock-acid rock reaction according to claim 1 is characterized in that: The determining of the actual diameter and fluid model corresponding to each pore channel based on the pore network model specifically includes: Determine a fluid model corresponding to each pore in the pore network model; the fluid model is an equivalent model of fluid flowing through each pore in the pore network model; Calculate the first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is the diameter change caused by chemical dissolution; Calculate the second diameter change corresponding to each hole; the second diameter change is the diameter change corresponding to each hole caused by stress; Calculating a total diameter change amount according to the first diameter change amount and the second diameter change amount, wherein the total diameter change amount is a diameter change amount that takes both dissolution and stress into consideration; The actual diameter corresponding to each channel is calculated based on the initial diameter corresponding to each channel and the total amount of diameter change.

4. The method for fluid-solid coupling numerical simulation of carbonate rock-acid rock reaction according to claim 3 is characterized in that: The calculating of the second diameter variation corresponding to each channel specifically includes: Calculate the total effective stiffness of the pore network model in each direction; calculating a macroscopic boundary displacement based on the total effective stiffness; Calculating the radial strain of each pore according to the macro boundary displacement; The second diameter variation is calculated according to the radial strain of each hole.

5. The method for fluid-solid coupling numerical simulation of carbonate rock-acid rock reaction according to claim 3 is characterized in that: The specific formula for calculating the first diameter change corresponding to each channel is: in, represents the first diameter change of the pore ij caused by chemical dissolution, Δt represents the reaction time, represents the initial acid concentration at node i, A ij represents the reaction surface area, d ij represents the diameter of the hole ij, q ij represents the volume flow rate in the pore ij, c sol represents the concentration of soluble substances on the pore wall, v represents the reaction order of the chemical reaction, represents the effective reaction rate coefficient, λ represents the surface reaction rate, D represents the molecular diffusion coefficient, and Sh represents the Sherwood number.

6. A carbonate rock acid-rock reaction fluid-solid coupling numerical simulation system, characterized in that: The system comprises: A CT scanning module is used to perform CT scanning on the core samples corresponding to the carbonate rock to obtain a CT scanning image; A pore network model building module, used to build a pore network model according to the CT scan image; A parameter determination module, used to determine the actual diameter corresponding to each pore channel and the fluid model based on the pore network model; the actual diameter corresponding to each pore channel is the diameter corresponding to each pore channel taking into account both dissolution and stress effects; A porosity calculation module, used to calculate the porosity based on the actual diameter corresponding to each pore; A permeability calculation module, used to calculate the permeability of the pore network model based on the fluid model corresponding to each pore channel; The calculation formula of the fluid model is: Among them, q ij represents the volume flow rate in the pore ij, d ij and l ij Represent the diameter and length of the pore ij, respectively, (P j -P i ) represents the pressure drop along the pore between the connecting node i and the node j, μ represents the viscosity of the fluid, i and j are both positive integers greater than 1, and i is not equal to j; The calculation formula of the permeability of the pore network model is: Where k represents the permeability of the pore network model, v represents the average flow velocity at the inlet of the pore network model, n represents the number of pores in the first row of the pore network model, μ represents the fluid kinematic viscosity, L represents the length of the pore network model along the flow direction, ΔP represents the pressure difference between the inlet and outlet of the pore network model, ΔP = P0-P s , P0 represents the initial injection pressure at the inlet end, P s Indicates the pressure at the outlet, q 1j represents the fluid model corresponding to the first row of pores in the pore network model, d ij Represents the diameter of the hole ij.

7. The carbonate rock-acid rock reaction fluid-solid coupling numerical simulation system according to claim 6 is characterized in that: The pore network model construction module specifically includes: An extraction unit, used for extracting sample parameter distribution on the CT scan image by using a watershed segmentation algorithm; An equivalent network determination unit, used to construct an equivalent network with a pore topological relationship according to the sample parameter distribution; The pore network model determination unit is used to process the equivalent network to obtain a pore network model.

8. The carbonate rock-acid-rock reaction fluid-solid coupling numerical simulation system according to claim 6, characterized in that: The parameter determination module specifically includes: A fluid model determination unit, used to determine the fluid model corresponding to each pore in the pore network model; the fluid model is an equivalent model of fluid flowing through each pore in the pore network model; A first diameter change calculation unit is used to calculate a first diameter change corresponding to each channel according to the fluid model corresponding to each channel; the first diameter change is a diameter change caused by chemical dissolution; A second diameter variation calculation unit is used to calculate a second diameter variation corresponding to each hole; the second diameter variation is a diameter variation corresponding to each hole caused by stress; a diameter change total amount calculation unit, used to calculate the diameter change total amount according to the first diameter change amount and the second diameter change amount, wherein the diameter change total amount is the diameter change amount that takes both dissolution and stress into consideration; The actual diameter calculation unit is used to calculate the actual diameter corresponding to each channel according to the initial diameter corresponding to each channel and the total amount of diameter change.

9. The carbonate rock-acid rock reaction fluid-solid coupling numerical simulation system according to claim 8, characterized in that: The second diameter change calculation unit includes: Total effective stiffness calculation subunit, used to calculate the total effective stiffness of the pore network model in each direction; A macro boundary displacement calculation subunit, used for calculating the macro boundary displacement according to the total effective stiffness; A radial strain calculation subunit, used for calculating the radial strain of each channel according to the macro boundary displacement; The second diameter variation calculation subunit is used to calculate the second diameter variation according to the radial strain of each hole.

10. The carbonate rock-acid rock reaction fluid-solid coupling numerical simulation system according to claim 8, characterized in that: The specific formula for calculating the first diameter change corresponding to each channel is: in, represents the first diameter change of the pore ij caused by chemical dissolution, Δt represents the reaction time, represents the initial acid concentration at node i, A ij represents the reaction surface area, d ij represents the diameter of the hole ij, q ij represents the volume flow rate in the pore ij, c sol represents the concentration of soluble substances on the pore wall, v represents the reaction order of the chemical reaction, represents the effective reaction rate coefficient, λ represents the surface reaction rate, D represents the molecular diffusion coefficient, and Sh represents the Sherwood number.

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