Shale formation modeling method and system suitable for hydraulic fracture propagation simulation

Abstract

The invention provides a shale formation modeling method and system suitable for hydraulic fracture propagation simulation, and belongs to the technical field of oil and gas reservoir development. The method comprises the following steps: dividing a lamina into three states according to a shale core test result, establishing a lamina model for the shale lamina in different states, and carrying out lamina state conversion under different stress conditions. According to the method, definite state division is carried out on the shale formation, and modeling is carried out on each state, so that the state can participate in fracturing coupling stress field calculation; the influence of the stripe layer which is not fully opened on the property of the shale is represented through transverse isotropy, so that the complexity caused by modeling each stripe layer is avoided; under a certain condition, the lamina is activated to become a solid crack, and complex crack characteristic simulation of lamina shale can also be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas reservoir development, and in particular relates to a shale lamination modeling method and system suitable for hydraulic fracture expansion simulation. Background Art

[0002] Shale oil and gas is one of the main frontiers for oil and gas resource development in my country. Usually, shale reservoirs need to use hydraulic fracturing technology to create volume fractures to form a high-conductivity fracture network, and then construct a flow channel between the oil and gas in the shale reservoir and the wellbore.

[0003] In the process of shale hydraulic fracturing, it is very important to select a certain fracturing model to simulate and calculate the expansion morphology of the fracturing cracks, analyze the fracture conductivity under the fracture morphology, and then optimize the fracturing construction parameters. In the existing fracturing model, the rock mechanics characteristics, natural fracture distribution characteristics, bedding characteristics, mineral composition characteristics, geostress characteristics and geochemical characteristics of the shale reservoir are fully considered, so that the morphology of the shale reservoir fracturing cracks can be more accurately evaluated. However, the current shale fracturing model cannot accurately describe the characteristics of shale laminations. In some shale reservoirs, the laminations are relatively developed, and the lamination density reaches hundreds of laminations / m. In this case, it is very cumbersome to model each lamination. Similarly, in the process of shale fracturing, only a small number of laminations can be activated, and most of the laminations cannot be fully opened. It is very complicated to establish hundreds of lamination models in numerical methods, resulting in huge calculations. Therefore, it is not reasonable to model each lamination by solid modeling of the interface between shale layers. Therefore, it is necessary to propose a reasonable and sufficiently concise shale lamination construction method for application in shale fracturing models. On the basis of fully describing the shale lamination characteristics, it does not significantly increase the amount of calculation, so that technicians can consider the shale reservoir lamination characteristics during the fracturing design optimization process, and provide help for guiding fracturing construction parameters. Summary of the invention

[0004] It is very important to optimize the fracturing parameters through numerical simulation before shale fracturing construction. However, for shale reservoirs with developed laminae, the existing fracturing models cannot fully describe the laminae, and simplified measures are usually taken, which makes it impossible to effectively analyze the impact of laminae on crack expansion. In order to solve the above problems, the present invention proposes a shale laminae modeling method and system suitable for hydraulic fracture expansion simulation, which can effectively consider the impact of shale laminae on crack expansion morphology in fracturing simulation, thereby improving the accuracy of fracturing simulation and providing effective help for fracturing design and parameter optimization.

[0005] The present invention is achieved through the following technical solutions:

[0006] A first aspect of the present invention provides a shale lamination modeling method suitable for hydraulic fracture extension simulation, wherein the lamination is divided into three states according to shale core test results, and lamination models are established for shale laminations in different states.

[0007] A further improvement of the present invention is:

[0008] The method comprises the following steps:

[0009] S10, obtaining shale core test data;

[0010] S20, classifying the shale lamination state according to the shale core test data;

[0011] S30, establishing a shale fluid-solid coupling model;

[0012] S40, establishing shale lamination models with different lamination states.

[0013] A further improvement of the present invention is:

[0014] The shale core test data in step S10 include but are not limited to geological interpretation data, logging data and core experimental test results. The core experimental test includes uniaxial compression test, triaxial compression test, tensile strength test, shear test, porosity and permeability test, electron microscope scanning or CT scanning microstructure test.

[0015] A further improvement of the present invention is:

[0016] In step S20, according to the core test data, the shale lamination states are divided into three types: ① fully closed shale laminations, ② partially closed shale laminations, and ③ open shale laminations.

[0017] A further improvement of the present invention is:

[0018] The operation of establishing the shale fluid-solid coupling model in step S30 includes:

[0019] Shale is assumed to be a pore elastic body. Shale has developed laminations with obvious differences in vertical and horizontal directions. Therefore, it is described by the transversely isotropic elastic constitutive equation, namely:

[0020] S=S0-α β p1I+C:ε (1-1)

[0021]

[0022] Where: S is the stress tensor; S0 is the initial stress, MPa; α β is the BIOT coefficient, dimensionless; p1 is the pore pressure in the formation, MPa; I is the unit tensor; C is the elastic parameter tensor; ε is the strain tensor; C11 , C 12 , C 13 , C 33 , C 44 are five independent elastic parameters of a transversely isotropic material;

[0023] The strain tensor of shale is characterized by the displacement:

[0024]

[0025] Where: u is the ground displacement, m;

[0026] The quasi-static momentum conservation equation for saturated poroelastic rock is as follows:

[0027]

[0028] Among them: F V is physical strength, N / m 2 ;

[0029] For flow in shales, the continuity equation is expressed as follows:

[0030]

[0031] Where: ∈ p1 is the formation porosity, %; ρ is the fluid density, 10 3 kg / m 3 ; u1 is the fluid velocity tensor, Q m It is the mass source of formation fluid flow, kg / (s·m 3 );

[0032] The compressibility of shale is controlled by porosity and pressure, and the compressibility of a fluid depends on density and pressure:

[0033]

[0034]

[0035] χ s =∈ p1 χ f +(1-∈ p1 ) p1 (1-8)

[0036] Where: p1 is the formation matrix compressibility, Pa -1 ; f is the fluid compressibility, Pa -1 ; s is the compressibility of the poroelastic formation, Pa -1 .

[0037] A further improvement of the present invention is:

[0038] The operation of establishing shale lamination models in different states in step S40 includes: for shale laminations in different states; wherein,

[0039] ③ The shale lamination is fully closed, and the lamination model is:

[0040]

[0041] Where: d f is the crack width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 ;

[0042] ④ The shale lamination is partially closed, and the lamination model is:

[0043]

[0044] Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 ; n indicates the difference multiple of equivalent permeability between shale in laminae-developed areas and shale in laminae-undeveloped areas, which can be measured by experimental data and is dimensionless;

[0045] ③ Shale lamination is open, and the lamination model is:

[0046]

[0047] Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; X f0 and X τ is the initial slip and slip increment on both sides of the laminae, m; and is the normal direction vector of the crack's two side walls; and is the force on both sides of the crack in the normal direction, N; k la is the permeability of a single stripe layer, μm 2 ; ff is the roughness coefficient of the layer, dimensionless.

[0048] A further improvement of the present invention is:

[0049] The state of shale lamination is not always constant. For a lamination, its initial state should be in one of the three states and will transform under certain conditions;

[0050] The conversion determination conditions are as follows:

[0051] (1) When the difference in shear stress on both sides of the shale laminae exceeds the sum of the friction force and the laminae shear strength, the laminae will be shear activated and the laminae will enter state ③ from state ① or ②. Otherwise, the laminae state will remain unchanged:

[0052]

[0053] in: and is the double-sided shear stress of shale lamination, MPa; μ s is the friction coefficient, dimensionless; τ f is the laminae shear strength, MPa; p is the fluid pressure in the fracture, σ3 is the vertical stress;

[0054] (2) For the shale laminae in state ①, when the bifacial normal stress of the laminae changes from the compression state to the tension state, it enters state ②. If the tensile stress exceeds the tensile strength, it enters state ③:

[0055]

[0056] Where: p is the fluid pressure in the fracture, σ3 is the vertical stress, σ t is the tensile strength of the laminae;

[0057] (3) The shear activation and tension activation of the laminae are independent of each other, that is, states ① and ② can enter state ③ through shear activation, while in the process of tension activation, state ① usually enters state ② first, and then enters state ③ from state ②;

[0058] (4) After displacement occurs on both sides of the lamination, fluid enters the lamination, causing it to no longer be completely closed. The discontinuity characteristics of the two sides cannot be eliminated. Therefore, the process of the lamination changing from state ① to state ②, and from state ② to state ③ is irreversible.

[0059] A second aspect of the present invention provides a shale lamination modeling system suitable for hydraulic fracture extension simulation, comprising:

[0060] A data acquisition unit, used for acquiring shale core test data;

[0061] A lamination state classification unit is used to classify the shale lamination state according to shale core test data;

[0062] Fluid-solid coupling model building unit, used to build a shale fluid-solid coupling model;

[0063] The laminae model building unit is used to build shale laminae models with different laminae states.

[0064] According to a third aspect of the present invention, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, the processor performs the following steps:

[0065] S10, obtaining shale core test data;

[0066] S20, classifying the shale lamination state according to the shale core test data;

[0067] S30, establishing a shale fluid-solid coupling model;

[0068] S40, establishing shale lamination models with different lamination states.

[0069] According to a fourth aspect of the present invention, a computer device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0070] S10, obtaining shale core test data;

[0071] S20, classifying the shale lamination state according to the shale core test data;

[0072] S30, establishing a shale fluid-solid coupling model;

[0073] S40, establishing shale lamination models with different lamination states.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] The method of the present invention clearly divides the states of shale laminations and models each state so that it can participate in the calculation of the coupled stress field of fracturing; the influence of insufficiently opened laminations on the properties of shale is characterized by transverse isotropy, thereby avoiding the tediousness of modeling each stripe layer. Under certain conditions, the laminations are activated and turned into solid fractures, which can also realize the simulation of complex fracture characteristics of laminar shale.

[0076] The present invention changes the previous analysis method of entity modeling of each stripe layer, proposes three lamination state models, fully describes the lamination, and provides a method for distinguishing the conversion of lamination states. It can be well combined with the existing fracturing model to further analyze the morphological characteristics of laminar shale fracturing cracks and provide assistance for the optimization of laminar shale fracturing parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 The present invention provides a flow chart of a shale lamination modeling method suitable for hydraulic fracture extension simulation;

[0078] Figure 2 This is a schematic diagram of the three-state model of shale lamination. DETAILED DESCRIPTION

[0079] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0080] In view of the fact that it is cumbersome and computationally difficult to model the laminae one by one in the current shale oil and gas volume fracturing design, the laminae characteristics are not fully considered and the fracture morphology simulation is inaccurate. The present invention proposes a shale laminae modeling method suitable for hydraulic fracture expansion simulation. The laminae are divided into three states according to the shale core test results, and laminae models are established for shale laminae in different states, and the laminae states are converted under different stress conditions. In the fracturing design, the laminae model is embedded in the fracturing model, so that the influence of the laminae on the fracture morphology during the expansion of the fracturing fracture can be simulated, and the fracturing construction parameters can be optimized based on this. This technical method can provide guidance and assistance for optimizing the fracturing parameters.

[0081] The present invention provides a shale lamination modeling method suitable for hydraulic fracture extension simulation, and an embodiment of the shale lamination modeling method is as follows:

[0082] [Example 1]

[0083] like Figure 1 As shown, the method comprises the following steps:

[0084] S10, obtaining shale core test data;

[0085] Before executing step S10, relevant data such as shale geology, logging and core test results can be collected and stored for subsequent use, including but not limited to: geological interpretation data, logging data, core experimental test results, etc. The core experimental test generally includes: uniaxial compression test, triaxial compression test, tensile strength test, shear test, porosity and permeability test, electron microscope scanning or CT scanning and other microstructure tests, etc.

[0086] S20, classifying the shale lamination state according to the shale core test data;

[0087] Based on the core test data of shale, the degree of shale lamination development, lamination openness and lamination density, as well as the differences in mechanical strength and permeability characteristics of shale in the vertical and longitudinal directions are clarified.

[0088] According to core test data, shale lamination states are divided into three types: Figure 2 As shown: ① shale laminations are fully closed, ② shale laminations are partially closed, and ③ shale laminations are open.

[0089] Specifically:

[0090] ① Shale laminae are fully closed

[0091] Shale laminations can be observed from electron microscope scanning or CT scanning results, but their opening is very small, or the laminations are filled with minerals such as clay, resulting in the laminations having no connectivity. The laminations do not show significant seepage capacity, and their seepage capacity is less than 10 times that of the shale matrix, which is not much different from the shale matrix. Such laminations can be considered to be fully closed.

[0092] ② Partial closure of shale laminae

[0093] From the microscopic scanning results, it was observed that the shale laminations have a certain degree of openness, or the internal clay is partially filled and has a certain flow channel. The lateral permeability of shale is larger than the longitudinal permeability. It can be considered that when the seepage capacity of the lamination reaches 10 to 100 times that of the matrix, the lamination is partially open, and this lamination can be considered partially closed.

[0094] ③ Shale lamination opening

[0095] Microscopic scanning observations show that shale laminations have a certain degree of openness, but there is no filling inside the laminations, the cracks are continuous, the lateral permeability of shale is dozens or even thousands of times greater than the longitudinal permeability (controlled by the lamination density), and when the lamination seepage capacity exceeds 100 times that of the matrix, the lamination is considered to be open.

[0096] In addition to the above seepage characteristic ratio differences, if the laminae opening is greater than 2 μm and there is no obvious filling, it can also be considered that the laminae are open.

[0097] S30, establishing a shale fluid-solid coupling model;

[0098] Shale is assumed to be a pore elastic body. Shale has developed laminations with obvious differences in vertical and horizontal directions. Therefore, it is described by the transversely isotropic elastic constitutive equation, namely:

[0099] S=S0-α β p1I+C:ε (1-1)

[0100]

[0101] Where: S is the stress tensor; s0 is the initial stress, MPa; α β is the BIOT coefficient, dimensionless; p1 is the pore pressure in the formation, MPa; I is the unit tensor; C is the elastic parameter tensor; ε is the strain tensor; C 11 , C12 , C 13 , C 33 , C 44 are five independent elastic parameters of a transversely isotropic material;

[0102] The strain tensor of shale can be characterized by displacement:

[0103]

[0104] Where: u is the ground displacement, m;

[0105] The quasi-static momentum conservation equation for saturated poroelastic rock is as follows:

[0106]

[0107] Among them: F V is physical strength, N / m 2 ;

[0108] For flow in shales, the continuity equation is expressed as follows:

[0109]

[0110] Where: ∈ p1 is the formation porosity, %; ρ is the fluid density, 10 3 kg / m 3 ; u1 is the fluid velocity tensor, Q m It is the mass source of formation fluid flow, kg / (s·m 3 );

[0111] The compressibility of shale is controlled by porosity and pressure, and the compressibility of a fluid depends on density and pressure:

[0112]

[0113]

[0114] χ s =∈ p1 χ f +(1-∈ p1 ) p1 (1-8)

[0115] Where: p1 is the formation matrix compressibility, Pa -1 ; f is the fluid compressibility, Pa -1 ; s is the compressibility of the poroelastic formation, Pa -1 .

[0116] S40, establishing shale lamination models in different states;

[0117] For shale laminae in different states, the models are as follows:

[0118] ⑤ Shale laminae are fully closed:

[0119] The shale lamination is completely closed, with full contact between the two sides and almost no gaps, and basically no discontinuous characteristics. At this time, the shale can be regarded as a continuous medium. Only its transverse isotropic characteristics need to be considered, including the differences in the elastic parameters, mechanical strength parameters and seepage capacity of the shale in the vertical and horizontal directions. These parameters can be obtained through core testing or logging interpretation. The state ① lamination model is:

[0120]

[0121] Where: d f is the crack width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 .

[0122] ⑥ Partial closure of shale laminae:

[0123] In this state, the shale lamination surface shows discontinuous characteristics, but the shale lamination has not been completely separated. There are still some cemented laminations whose displacement on both sides can be considered continuous and have a certain tensile strength. At this time, the shale lamination is set as a closed seepage fracture. Compared with state ①, the lamination has an additional effect on the lateral seepage capacity of shale. However, in the model, it is not modeled separately. Instead, the effect of the lamination on the lateral seepage capacity is characterized by the lateral permeability, which is controlled by the conductivity of the single stripe layer and the density of the lamination. The lateral permeability of shale can be obtained through core testing. The state ② lamination model is:

[0124]

[0125] Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 ; n indicates the difference multiple of the equivalent permeability between shales in the laminae-developed area and the laminae-undeveloped area, which can be measured by experimental data and is dimensionless.

[0126] ⑦ Shale lamination opening:

[0127] The two sides of the shale lamination have been separated, and the lamination should be regarded as a crack. In this state, the lamination has a great influence on the seepage capacity, mechanical strength, and continuity of the shale, and the lamination displacement discontinuity characteristics need to be considered. The lamination needs to be modeled separately for cracks. At this time, the lamination forms a flow advantage channel, and the lamination's separate fracture flow needs to be considered. At this time, the shale can be regarded as a dual medium composed of cracks and matrix communication. The influence of lamination on the porosity and mechanical strength characteristics of the rock can be obtained through core testing. The state ③ lamination model is:

[0128]

[0129] Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; X f0 and X τ is the initial slip and slip increment on both sides of the laminae, m; and is the normal direction vector of the crack's two side walls; and is the force on both sides of the crack in the normal direction, N; k la is the permeability of a single stripe layer, μm 2 ;f f is the laminae roughness coefficient, dimensionless.

[0130] The states of the above three types of shale laminations are not always constant. For a lamination, its initial state should be in one of the above three states and will transform under certain conditions.

[0131] The conversion determination conditions are as follows:

[0132] (1) When the difference in shear stress on both sides of the shale laminae exceeds the sum of the friction force and the laminae shear strength, the laminae will be shear activated and the laminae will enter state ③ from state ① or ②. Otherwise, the laminae state will remain unchanged:

[0133]

[0134] in: and is the double-sided shear stress of shale lamination, MPa; μ s is the friction coefficient, dimensionless; τ f is the laminae shear strength, MPa; p is the fluid pressure in the fracture, σ3 is the vertical stress;

[0135] (2) For the shale laminae in state ①, when the bifacial normal stress of the laminae changes from the compression state to the tension state, it enters state ②. If the tensile stress exceeds the tensile strength, it enters state ③:

[0136]

[0137] Where: p is the fluid pressure in the fracture, σ3 is the vertical stress, σ t is the tensile strength of the laminae;

[0138] (3) The shear activation and tension activation of the laminae are independent of each other, that is, states ① and ② can enter state ③ through shear activation, while in the process of tension activation, state ① usually enters state ② first, and then enters state ③ from state ②;

[0139] (4) After displacement occurs on both sides of the lamination, fluid enters the lamination, causing it to no longer be completely closed. The discontinuity characteristics of the two sides cannot be eliminated. Therefore, the process of the lamination changing from state ① to state ②, and from state ② to state ③ is irreversible.

[0140] The above-mentioned shale lamination model is embedded in the fracturing model. During the hydraulic fracture expansion process, the coupled stress state of shale in the lamination development period is judged in real time. When the lamination meets the activation conditions, the corresponding state conversion is performed, and the model is selected according to its corresponding state. The shale lamination model after the state conversion is updated to the fracturing model, and the fracture expansion calculation is continued, thereby realizing the simulation analysis of fracturing crack expansion of laminar shale.

[0141] The embodiments of the method of the present invention are as follows:

[0142] [Example 2]

[0143] A horizontal well was drilled sideways in a shale reservoir, with a reservoir depth of about 3200m, casing completion, and a horizontal section length of 1000m. In the early stage, shale cores of the reservoir section were obtained through coring of the pilot well, and related basic experimental tests were carried out. The lamination model provided by this patent was combined with the well fracturing design to simulate the fracture extension. The specific implementation steps are as follows:

[0144] (1) Based on the geological parameters and logging data of this well combined with the core test results, the geological and mechanical characteristics of this well were interpreted. The shale target section of this well has developed laminations, the target sub-layer height is 24m, and the lamination density is about 30 / m. From the core CT scan, the lamination has a certain initial opening, about 10-20μm, but there is clay cementation within the layer, so it is determined that the lamination is in state ②. The ground stress state is a reverse fault state, and the three-dimensional ground stress distribution (vertical ground stress / horizontal maximum ground stress / horizontal minimum ground stress) is about 64 / 66 / 56MPa, the formation pressure coefficient is 1.4, the elastic modulus is 26-28GPa, the Poisson's ratio is 0.23, and the rock tensile strength is 4.5MPa.

[0145] (2) According to the fracturing design of this well, it is determined that the well is divided into 19 sections for fracturing, with 2 to 4 clusters of perforations in each section, 18 to 30 spiral perforations in each cluster, an angle of 60°, a hole diameter of 9.5 mm, and a perforation interval of 1 m. The fracturing displacement is controlled at 10 to 16 m 3 / min, single-stage liquid volume is about 1410~1550m 3 , sand ratio is 5.2% to 5.9%. Whether to add temporary plugging agent depends on the on-site fracturing situation.

[0146] (3) Taking the third stage fracturing design as an example, this stage has three perforations, with a cluster spacing of 10 m, and uses low-viscosity slick water (2-3 mPa·s) with a scale of 1250 m 3 , high viscosity slippery water (30~40mPa·s) scale is 200m 3 , acid 20m 3 (concentration 20%), 70 / 140 mesh proppant scale 20m 3 , 40 / 70 mesh proppant scale is 50m 3 , 30 / 50 mesh proppant scale is 10m 3 Temporary plugging agent (40 / 70 mesh and 30 / 50 mesh, ratio 1:1) scale 0.3m 3 .

[0147] (4) Establishing a fracturing model. According to the above parameters, a fracturing crack extension model is established. This embodiment uses a three-dimensional finite element fracturing model based on a discontinuous discrete fracture model, and embeds the laminar model of the present invention, but the fracturing model applicable to the present invention is not limited to the finite element fracturing model. The perforation cluster is simplified to an initial hydraulic fracture, and the boundary conditions and initial conditions are loaded on the model to calculate the initial stress distribution state of the model.

[0148] (5) Conduct fracture morphology simulation. According to the fracturing design parameters, fracture morphology simulation is conducted to obtain the fracture extension morphology. In this embodiment, when the injection volume reaches 940m 3 , displacement is 16m 3 / min, when the liquid is low viscosity slick water, the lamination is activated and a laminar fracture is formed. The simulation results show that the crack length is 210m 3 The fracture height is 28m, and the lamination extension range is about 110m along the direction of minimum geostress and 80m along the direction of maximum geostress.

[0149] (6) Optimization of fracturing parameters. Since the cracks activated the laminae, a large amount of shale was lost laterally, which affected the expansion of the length and height of the cracks. Therefore, it was necessary to optimize the fracturing parameters. According to the optimization results, the amount of pre-adhesive high viscosity was increased from 200m 3 Increase to 260m 3 , and control the early displacement rate, fracturing from 800m 3Medium viscosity slick water (9-12 mPa·s) was used to reduce the liquid penetration along the laminae and reduce the possibility of laminae opening. The simulation results after parameter optimization showed that the fracture length was 260 m 3 The fracture height is 36m and the laminae are not open. The fracture morphology parameters have been significantly improved.

[0150] (7) Fracturing simulation of other sections Repeat steps (3) to (6) to simulate and optimize the fracture parameters of all fracturing sections until a relatively ideal fracture morphology is obtained.

[0151] The present invention also provides a shale lamination modeling system suitable for hydraulic fracture extension simulation, and an embodiment of the system is as follows:

[0152] [Example 3]

[0153] The system comprises:

[0154] A data acquisition unit, used for acquiring shale core test data;

[0155] A lamination state classification unit is used to classify the shale lamination state according to shale core test data;

[0156] Fluid-solid coupling model building unit, used to build a shale fluid-solid coupling model;

[0157] The laminae model building unit is used to build shale laminae models with different laminae states.

[0158] The present invention also provides a computer-readable storage medium, and the computer-readable storage medium embodiment is as follows:

[0159] [Example 4]

[0160] The computer readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor performs the following steps:

[0161] S10, obtaining shale core test data;

[0162] S20, classifying the shale lamination state according to the shale core test data;

[0163] S30, establishing a shale fluid-solid coupling model;

[0164] S40, establishing shale lamination models with different lamination states.

[0165] The present invention also provides a computer device, and the embodiments of the computer device are as follows:

[0166] [Example 5]

[0167] The computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0168] S10, obtaining shale core test data;

[0169] S20, classifying the shale lamination state according to the shale core test data;

[0170] S30, establishing a shale fluid-solid coupling model;

[0171] S40, establishing shale lamination models with different lamination states.

[0172] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A shale lamination modeling method suitable for hydraulic fracture extension simulation, characterized in that: According to the shale core test results, the laminations are divided into three states, and lamination models are established for shale laminations in different states.

2. The shale lamination modeling method according to claim 1, characterized in that: The method comprises the following steps: S10, obtaining shale core test data; S20, classifying the shale lamination state according to the shale core test data; S30, establishing a shale fluid-solid coupling model; S40, establishing shale lamination models with different lamination states.

3. The shale lamination modeling method according to claim 2, characterized in that: The shale core test data in step S10 include but are not limited to geological interpretation data, logging data and core experimental test results. The core experimental test includes uniaxial compression test, triaxial compression test, tensile strength test, shear test, porosity and permeability test, electron microscope scanning or CT scanning microstructure test.

4. The shale lamination modeling method according to claim 3, characterized in that: In step S20, according to the core test data, the shale lamination states are divided into three types: ① fully closed shale laminations, ② partially closed shale laminations, and ③ open shale laminations.

5. The shale lamination modeling method according to claim 4, characterized in that: The operation of establishing the shale fluid-solid coupling model in step S30 includes: Shale is assumed to be a pore elastic body. Shale has developed laminations with obvious differences in vertical and horizontal directions. Therefore, it is described by the transversely isotropic elastic constitutive equation, namely: S=S0-a β p1I+C:e (1-1) Where: S is the stress tensor; S0 is the initial stress, MPa; α β is the BIOT coefficient, dimensionless; p1 is the pore pressure in the formation, MPa; I is the unit tensor; C is the elastic parameter tensor; ε is the strain tensor; C 11 , C 12 , C 13 , C 33 , C 44 are five independent elastic parameters of a transversely isotropic material; The strain tensor of shale is characterized by the displacement: Where: u is the ground displacement, m; The quasi-static momentum conservation equation for saturated poroelastic rock is as follows: Among them: F V is physical strength, N / m 2 ; For flow in shales, the continuity equation is expressed as follows: Where: ∈ p1 is the formation porosity, %; ρ is the fluid density, 10 3 kg / m 3 ; u1 is the fluid velocity tensor, Q m It is the mass source of formation fluid flow, kg / (s·m 3 ); The compressibility of shale is controlled by porosity and pressure, and the compressibility of a fluid depends on density and pressure: x s =∈ p1 x f +(1-∈ p1 )x p1 (1-8) Where: p1 is the formation matrix compressibility, Pa -1 ; f is the fluid compressibility, Pa -1 ; s is the compressibility of the poroelastic formation, Pa -1 .

6. The shale lamination modeling method according to claim 5, characterized in that: The operation of establishing shale lamination models in different states in step S40 includes: for shale laminations in different states; wherein, ① The shale lamination is fully closed, and the lamination model is: Where: d f is the crack width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 ; ② The shale lamination is partially closed, and the lamination model is: Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; k sf and k sh are the equivalent permeabilities of shales in the laminae-developed and laminae-undeveloped areas, μm 2 ; n indicates the difference multiple of equivalent permeability between shale in laminae-developed areas and shale in laminae-undeveloped areas, which can be measured by experimental data and is dimensionless; ③ Shale lamination is open, and the lamination model is: Where: d f is the crack width, m; d f0 is the initial laminae width, m; X f is the laminar shear slip, m; X f0 and X τ is the initial slip and slip increment on both sides of the laminae, m; and is the normal direction vector of the crack's two side walls; and is the force on both sides of the crack in the normal direction, N; k la is the permeability of a single stripe layer, μm 2 ;f f is the laminae roughness coefficient, dimensionless.

7. The shale lamination modeling method according to claim 6, characterized in that: The state of shale lamination is not always constant. For a lamination, its initial state should be in one of the three states and will transform under certain conditions; The conversion determination conditions are as follows: (1) When the difference in shear stress on both sides of the shale laminae exceeds the sum of the friction force and the laminae shear strength, the laminae will be shear activated and the laminae will enter state ③ from state ① or ②. Otherwise, the laminae state will remain unchanged: in: and is the double-sided shear stress of shale lamination, MPa; μ s is the friction coefficient, dimensionless; τ f is the laminae shear strength, MPa; p is the fluid pressure in the fracture, σ3 is the vertical stress; (2) For the shale laminae in state ①, when the bifacial normal stress of the laminae changes from the compression state to the tension state, it enters state ②. If the tensile stress exceeds the tensile strength, it enters state ③: Where: p is the fluid pressure in the fracture, σ3 is the vertical stress, σ t is the tensile strength of the laminae; (3) The shear activation and tension activation of the laminae are independent of each other, that is, states ① and ② can enter state ③ through shear activation, while in the process of tension activation, state ① usually enters state ② first, and then enters state ③ from state ②; (4) After displacement occurs on both sides of the lamination, fluid enters the lamination, causing it to no longer be completely closed. The discontinuity characteristics of the two sides cannot be eliminated. Therefore, the process of the lamination changing from state ① to state ②, and from state ② to state ③ is irreversible.

8. A shale lamination modeling system suitable for hydraulic fracture extension simulation, characterized in that: include: A data acquisition unit, used for acquiring shale core test data; A lamination state classification unit is used to classify the shale lamination state according to shale core test data; Fluid-solid coupling model building unit, used to build a shale fluid-solid coupling model; The laminae model building unit is used to build shale laminae models with different laminae states.

9. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the method according to any one of claims 1 to 7.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 7.

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