A reservoir compressibility evaluation method and system considering shale lamination development characteristics

Abstract

The present application relates to a kind of reservoir compressibility evaluation method and system considering shale lamina development characteristics, belong to shale oil and gas development geology field;Including: step 1: the experimental study of the influence of shale lamina development characteristics on mechanical properties;Step 2: the influence of shale lamina on tensile properties is researched;Step 3: the influence of shale lamina on compressive properties is researched;Step 4: the longitudinal fracturing fracture network layer-penetrating physical simulation experiment considering lamina stress barrier zone;Step 5: the longitudinal fracturing fracture network layer-penetrating finite element numerical simulation considering lamina stress barrier zone;Step 6: the influence law of lamina development characteristics on the behavior of hydraulic fracture layer-penetrating is researched;Step 7: the fracturing property evaluation index of shale reservoir is established;Step 8: target block dominant lamina combination distribution position and reservoir compressibility evaluation.The present application realizes the maximum of shale gas development's reserve producing rate, recovery efficiency, yield rate, provides theoretical basis and technical support for efficient development of shale gas reservoir.

Description

Technical Field

[0001] This invention belongs to the field of shale gas development geology, specifically relating to a reservoir compressibility evaluation method and system that considers the development characteristics of shale laminae. Background Technology

[0002] Fracturability refers to the property of shale to fracture under water pressure, forming an effective and complex network of fractures, thereby increasing production capacity. In my country, continental lacustrine shale exhibits strong heterogeneity and significant differences in laminar structure, resulting in complex fracturability, which severely impacts the development of shale oil and gas. However, research on the influence of differences in laminar structure on fracturability in fine-grained sedimentary rocks is still in its early stages. Currently, most related studies both domestically and internationally focus on the brittleness of fine-grained sedimentary rocks, rather than fracturability. Many scholars believe that the content of brittle minerals is an important factor affecting the development of natural or artificial fractures. However, the fracturability of shale, besides being closely related to its brittle minerals, is also related to its mechanical properties such as horizontal stress and fracture toughness, which are closely related to the degree of laminar development. Factors such as the degree of laminar development, laminar thickness, thickness variation, laminar continuity, morphology, and geometric relationships have a significant impact on rock mechanical properties and the intrinsic factors of fracture propagation. However, research on the detailed identification of marine shale laminar layers in southern Sichuan and their impact on fracturability is still very limited. In particular, previous studies have mostly failed to make precise distinctions between laminae, laminae groups, and layers. The developmental degree, composition, structure, and bedding of each of these three elements, and how they affect fracturability, remain a completely new area of ​​research. Summary of the Invention

[0003] This invention addresses the lack of theoretical and technical support and the incompleteness of existing reservoir compressibility evaluation methods. It provides a quantitative and qualitative analysis method for reservoir compressibility evaluation that considers lamination development characteristics, employing indoor experiments, physical simulations, and finite element analysis. Based on research into the correlation between the mechanical properties of shale laminations and the fracture network, this invention establishes a compressibility evaluation index for shale reservoirs that considers lamination development characteristics. It clarifies the characteristics and distribution of high-quality laminations, reveals the degree and mechanism of their influence on reservoir properties, rock mechanical properties, and compressibility, and establishes analytical and evaluation techniques in this field. This provides a theoretical basis for the optimal selection of vertical targets in the Wufeng-Longmaxi Formation shale reservoirs, lays a theoretical foundation for the accurate division of vertical development strata and the rational selection of targets in shale reservoirs, further promotes the refined description and large-scale efficient development of shale gas reservoirs, maximizes the reserve utilization rate, recovery rate, and profitability of shale gas development, and provides theoretical basis and technical support for the efficient development of shale gas reservoirs.

[0004] The technical solution provided by this invention to solve the above-mentioned technical problems is as follows: Based on the classification and division of shale laminae and the quantitative statistics of parameters such as laminae density and thickness, and laminae combination density and thickness, the reservoir differences of different laminae combinations in each sublayer are qualitatively and quantitatively analyzed through permeability, CO2 / N2 adsorption, high-pressure mercury intrusion porosimetry, and scanning electron microscopy observation, thus establishing a method for evaluating the reservoir differences of different laminae combinations in shale reservoirs.

[0005] The technical solution of this invention is as follows:

[0006] A reservoir compressibility evaluation method considering shale lamination development characteristics includes:

[0007] Step 1: Experimental study on the influence of shale lamination development characteristics on mechanical properties: Based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes were designed for shale lamination development characteristics, and the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamination combinations were analyzed.

[0008] Step 2: Study on the influence of shale lamination on tensile properties: By conducting Brazilian splitting tests on shale with different lamination groups, the differences in crack propagation modes and fracture ultimate loads are studied. Then, the fluctuation of the stress-strain curve after the peak value is used to study the complexity of crack propagation. A correlation chart between relevant parameters of shale lamination structure and fracture toughness is established, and the influence of shale lamination on tensile properties is comprehensively analyzed.

[0009] Step 3: Study on the influence of shale laminae on compressive properties: Pseudo-triaxial tests were conducted on shale with different laminae to observe the differences in artificial crack propagation morphology. Different confining pressure conditions were designed to obtain the ultimate fracture load of shale with different laminae. The brittleness index calculated by Young's modulus and Poisson's ratio obtained from rock mechanics tests was used to characterize shale brittleness. The influence of laminae composition on reservoir brittleness was analyzed, and the influence of shale laminae on compressive properties was comprehensively analyzed.

[0010] Step 4: Consider the longitudinal pressure fracture network penetrating the layer physical simulation experiment of the layer stress barrier zone: use artificial layered rock samples to simulate the pressure fracturing test, and use the true triaxial loading method to restore the relative magnitude of the triaxial principal stress of the formation. Each sub-layer is cast with pure cement and different proportions of quartz sand or soil to make different physical and mechanical parameters. Design different tests to study the law of crack propagation under different interlayer physical property parameter comparisons.

[0011] Step 5: Considering the longitudinal pressure fracture network penetrating the layer with the layer stress barrier: Based on the cohesive finite element method, the interaction mechanism between hydraulic fractures and bedding planes is studied, and the influence of vertical stress and interface strength on the penetrating behavior of hydraulic fractures is revealed.

[0012] Step 6: Study on the influence of lamination development characteristics on the cross-layer behavior of hydraulic fractures: Based on the results of physical simulation experiments and finite element numerical simulations, the influence of interlayer stress difference, layer interface properties, and vertical stress caused by lamination on the propagation behavior of fractures at interlayer interfaces is analyzed.

[0013] Step 7: Establish evaluation indexes for the fracturability of shale reservoirs: Based on the key factors affecting reservoir fracturability identified in the research, and considering the control effect of key factors on the fracturability of shale reservoirs, establish evaluation parameters for shale fracturability, and then normalize them to the same standard using the range standardization method. For indices that are affected by multiple factors, multiplication and division of different factors are used to integrate their mutual influence.

[0014] Step 8: Evaluation of the distribution location of the dominant lamellar combination in the target block and the reservoir compressibility: Based on the compressibility characteristics, combined with the distribution of high-quality lamellars, reservoir physical properties, mechanical properties and compressibility, a lamellar iron pillar is established to clarify the distribution location of the dominant lamellar combination in the target block and the reservoir compressibility.

[0015] According to a preferred embodiment of the present invention, step 2 includes the following specific implementation process:

[0016] Based on the crack propagation morphology, the cracks in the samples are classified into central vertical cracks, eccentric arc-shaped cracks, and branched cracks. Central vertical cracks are pure tensile fracture failures with a single crack propagation mode, and the samples with this failure mode have the highest ultimate fracture load. The samples with eccentric arc-shaped cracks have a lower ultimate fracture load than those with central vertical cracks. The samples with branched cracks have the lowest ultimate fracture load.

[0017] Based on the morphology of the fracture surface, fracture toughness is classified into three types: type I (opening), type II (staggered), and type III (tearing). The empirical formula for type I fracture toughness is used for calculation.

[0018] ;

[0019] In the formula, K 1c For type I fracture toughness, P max B is the maximum destructive load value of the Brazilian splitting fracture, kN; B is the sample thickness, cm; D is the diameter, cm. Stress intensity factor;

[0020] Establish a graph showing the correlation between relevant parameters of shale laminar structure and fracture toughness;

[0021] According to a preferred embodiment of the present invention, step 3 specifically includes the following steps:

[0022] Step 3.1: Conduct pseudo-triaxial tests on shale with different lamellar groups to observe and clarify the differences in artificial crack propagation morphology in shale with different lamellar combinations;

[0023] Step 3.2: Design different confining pressure conditions to obtain the ultimate fracture load of shale with different layer combinations;

[0024] Step 3.3: Compare the characteristics of elastic modulus and Poisson's ratio of different texture groups based on the experimental results;

[0025] The lamellar groups corresponding to the elastic modulus from large to small are as follows: the overall pattern is a graded thin silt-thick mud lamellar combination, a graded thick silt-thick mud lamellar combination, a graded medium-thick silt-mud lamellar combination, an interbedded thick silt-thick mud lamellar combination, a graded thick mud lamellar combination, and a massive lamellar combination shale.

[0026] The laminar groups corresponding to Poisson's ratio from smallest to largest are as follows: graded thin silt-thick mud laminar group, graded medium-thick silt-mud laminar group, graded thick silt-thin mud laminar group, interbedded thick silt-thin mud laminar group, massive laminar group, and graded thick mud laminar group.

[0027] Step 3.4: Evaluate the influence of laminar composition on reservoir brittleness. The brittleness index is calculated using Young's modulus and Poisson's ratio obtained from rock mechanics tests, which characterizes shale brittleness. As shown below:

[0028] ;

[0029] ;

[0030] ;

[0031] Where YM represents the static Young's modulus, GPa; YM max Represents the maximum static Young's modulus, GPa; YM min Represents the minimum static Young's modulus, GPa; YM Brit PR represents the normalized Young's modulus, 0~1; PR represents the static Poisson's ratio, dimensionless; PR max Represents the maximum static Poisson's ratio, dimensionless; PR min Represents the minimum static Poisson's ratio, dimensionless; PR Brit Represents the normalized static Poisson ratio, 0~1;

[0032] Establish a table showing the relationship between mineral composition and brittleness index. This involves selecting shale samples with different mineral compositions, calculating the corresponding brittleness index, and then establishing the table showing the relationship between mineral composition and brittleness index.

[0033] According to a preferred embodiment of the present invention, the specific implementation process of step 4 is as follows:

[0034] Conduct simulated fracturing tests, including:

[0035] The first step is to perform layered medium simulation;

[0036] The second step is to perform layered geostress simulation;

[0037] The third step is to simulate the mechanical differences between layers; each sub-layer is cast using pure cement and different proportions of quartz sand or clay, resulting in different physical and mechanical parameters.

[0038] The fourth step is to simulate the interface strength. During the layered casting process, different interface strengths are simulated by varying the time interval between the two layers.

[0039] The study investigated the effects of differences in elastic modulus, interfacial bonding strength, and interlayer stress.

[0040] The effect of differences in elastic modulus includes:

[0041] Four sets of experiments were designed to discuss and study the crack propagation law under different interlayer physical property parameter comparisons, and to study how much the difference in elastic modulus comparisons affects whether cracks can penetrate the interlayer interface and enter the interlayer.

[0042] Influence of interfacial bonding strength; including:

[0043] Design several sets of experiments, with each layer of the specimen having the same composition; the differences are the properties of the layer interface, the fracturing fluid used in the experiment, the experimental loading rate, and the magnitude of the pressure on the interface; investigate the effects of different interface properties, interface stress conditions, and experimental loading rates on crack morphology for the same specimen.

[0044] According to a preferred embodiment of the present invention, step 5 includes the following specific implementation process:

[0045] The two influencing parameters, in-situ stress and bedding plane strength, are treated dimensionlessly, and the vertical stress difference coefficient is defined as:

[0046] ;

[0047] In the formula, —Vertical stress difference coefficient, dimensionless; —Minimum horizontal ground stress, ; —Vertical stress, .

[0048] The dimensionless composite bedding strength is defined by the relative magnitudes of the tensile strength of the underlying rock strata and the cohesion in the two tangential directions, i.e.:

[0049] ;

[0050] In the formula, —Lamination tensile strength, ; —Tensile strength of the lower rock strata, ; -index, ; — Cohesive forces along the first or second tangential direction of the bedding plane; —The cohesive force in the first or second tangential direction of the lower rock strata;

[0051] By continuously adjusting the tensile strength, cohesion, and vertical stress of the bedding plane, the vertical cross-bedding propagation law of hydraulic fractures under different vertical stress difference coefficients and bedding plane strengths was studied. After the simulation, three typical fracture morphologies were shown according to the different interaction modes between the hydraulic fractures and the bedding plane: T-shaped fractures, passivated fractures accompanied by bedding slip, and cross-bedding fractures that penetrate the bedding plane.

[0052] Draw a comprehensive control chart; the lower the strength of the bedding plane and the smaller the vertical stress difference coefficient, the easier it is to form a T-shaped joint; the lower the strength of the bedding plane and the larger the vertical stress difference coefficient, the easier it is to form a passivation joint; the higher the strength of the bedding plane and the larger the vertical stress difference coefficient, the easier it is to form a cross-layer joint.

[0053] According to a preferred embodiment of the present invention, step 6 includes the following specific implementation process:

[0054] The grey relational analysis method was used to evaluate and rank the factors influencing the fracturing index; the specific analysis included the following steps:

[0055] Determine a reference sequence;

[0056] Dimensionlessize all sequences;

[0057] The correlation coefficient C is calculated using the following formula;

[0058] ;

[0059] in, It is the minimum absolute difference between the reference sequence and the subsequence. ρ is the maximum absolute difference between the reference sequence and the subsequence, ρ is the resolution coefficient, and X is the absolute difference between each value of the reference sequence and the subsequence.

[0060] The correlation coefficients between the subsequence and the reference sequence are averaged to obtain the correlation between the reference sequence and a certain subsequence.

[0061] Sort according to the correlation between the reference sequence and the subsequence.

[0062] According to a preferred embodiment of the present invention, step 7 is specifically implemented as follows:

[0063] Three parameters, namely brittleness index, fracture toughness, and compressive strength, which take into account lamination development characteristics, are used to evaluate the fracturability of shale.

[0064] Normalize to the same standard using the range standardization method:

[0065] ;

[0066] ;

[0067] In the formula, Y represents the positive standardized value of the indicator; Y1 represents the negative standardized value of the indicator; and X represents the normal value of the indicator. The maximum value of the characterization index X; The minimum value of the characterization index X;

[0068] By multiplying and dividing the three normalized indices, a fracturability index combining the static brittleness index, fracture toughness, and triaxial compressive strength under confining pressure is established:

[0069] ;

[0070] In the formula, F is the fracturability index, which is dimensionless; B is the static brittleness index after positive normalization, which is dimensionless; K is the fracture toughness after negative normalization, which is dimensionless; and σ is the triaxial compressive strength after negative normalization, which is dimensionless.

[0071] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the above-described method for evaluating reservoir compressibility considering shale lamination development characteristics.

[0072] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method for evaluating reservoir compressibility considering shale lamination development characteristics.

[0073] A reservoir compressibility assessment system considering shale lamination development characteristics includes:

[0074] The module for studying the influence of shale lamination development characteristics on mechanical properties is configured as follows: based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes are designed for shale lamination development characteristics to analyze the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamination combinations.

[0075] The module for studying the influence of shale lamination on tensile properties is configured as follows: by conducting Brazilian splitting tests on shale with different lamination groups, the module studies the differences in crack propagation modes and fracture ultimate loads, and then studies the complexity of crack propagation by reflecting the fluctuation of the stress-strain curve after the peak value. The module establishes a graph showing the correlation between relevant parameters of shale lamination structure and fracture toughness, and comprehensively analyzes the influence of shale lamination on tensile properties.

[0076] The module for studying the influence of shale lamination on compressive properties is configured as follows: conducting pseudo-triaxial tests on shale with different lamination groups, observing the differences in artificial crack propagation morphology in shale with different lamination combinations, designing different confining pressure conditions to obtain the ultimate fracture load of shale with different lamination combinations, characterizing shale brittleness by calculating the brittleness index using Young's modulus and Poisson's ratio obtained from rock mechanics tests, analyzing the influence of lamination components on reservoir brittleness, and comprehensively analyzing the influence of shale lamination on compressive properties;

[0077] The longitudinal pressure fracture network through-layer physical simulation experiment module is configured as follows: Considering the stress barrier zone of the laminar fracture network, the longitudinal pressure fracture network through-layer physical simulation experiment is conducted using artificial layered rock samples to simulate the pressure fracture test. The relative magnitude of the triaxial principal stress of the formation is restored by true triaxial loading. Each sub-layer is cast with pure cement and different proportions of quartz sand or soil to achieve different physical and mechanical parameters. Different experiments are designed to study the law of fracture propagation under different interlayer physical property parameter comparisons.

[0078] The longitudinal pressure fracture network penetration finite element numerical simulation module is configured as follows: longitudinal pressure fracture network penetration finite element numerical simulation considering the lamellar stress barrier zone: based on the cohesive finite element method, the mechanism of interaction between hydraulic fractures and bedding planes is studied, and the influence of vertical stress and interface strength on the penetration behavior of hydraulic fractures is revealed.

[0079] The module for studying the influence of lamination development characteristics on the cross-layer behavior of hydraulic fractures is configured as follows: based on the results of physical simulation experiments and finite element numerical simulations, the influence of interlayer stress difference, layer interface properties, and vertical stress caused by lamination on the propagation behavior of fractures at interlayer interfaces is analyzed.

[0080] The module for establishing fracturability evaluation indicators is configured as follows: based on the key factors affecting reservoir fracturability identified in the research, the control effect of key factors on shale reservoir fracturability is comprehensively considered, and evaluation parameters for shale fracturability are established. Then, the parameters are normalized to the same standard using the range standardization method. For indicators that are affected by multiple factors, the multiplication and division of different factors are used to comprehensively reflect their mutual influence.

[0081] The compressibility evaluation module is configured as follows: Distribution location of advantageous lamellar combinations in the target block and reservoir compressibility evaluation: Based on compressibility characteristics, combined with the distribution of high-quality lamellars, reservoir physical properties, mechanical properties and compressibility, establish lamellar iron pillars to clarify the distribution location of advantageous lamellar combinations in the target block and reservoir compressibility.

[0082] The beneficial effects of this invention are as follows:

[0083] This invention provides a quantitative and qualitative analysis method for reservoir compressibility evaluation considering lamination development characteristics, employing indoor experiments, physical simulations, and finite element simulations. Based on research into the correlation between the mechanical properties of shale laminations and the fracture network penetration through layers, this invention establishes a compressibility evaluation index for shale reservoirs considering lamination development characteristics. It clarifies the characteristics and distribution of high-quality laminations, reveals the degree and mechanism of influence of lamination development characteristics on reservoir properties, rock mechanical properties, and compressibility, and forms an analytical and evaluation technique in this field. This provides a theoretical basis for the optimal selection of vertical targets in the Wufeng-Longmaxi Formation shale reservoirs, and lays the theoretical foundation for accurate division of vertical development strata and rational target selection in shale reservoirs. It has advantages such as wide applicability, high efficiency, and high accuracy, and can provide theoretical basis and technical support for the efficient development of shale gas reservoirs. Attached Figure Description

[0084] Figure 1 This is a schematic diagram of the Brazilian splitting test characteristics of different lamellar combinations in block A of the present invention;

[0085] Figure 2 The correlation diagram of average laminar density and fracture toughness in block A;

[0086] Figure 3 The correlation diagram of the average thickness of the laminae group in block A with fracture toughness;

[0087] Figure 4 Triaxial compressive stress-strain curves of shale with different laminae in Block A;

[0088] Figure 5 Box plot showing the elastic modulus and Poisson's ratio of shale with different laminae in Block A;

[0089] Figure 6 This is a schematic diagram illustrating the influence of siliceous minerals in block A on the brittleness index.

[0090] Figure 7 This is a schematic diagram illustrating the influence of clay minerals in block A on the brittleness index.

[0091] Figure 8 This is a schematic diagram illustrating the influence of calcareous minerals in block A on the brittleness index.

[0092] Figure 9A schematic diagram of the structural dimensions of a simulated fracturing specimen;

[0093] Figure 10 This is a geometric model diagram;

[0094] Figure 11 A comparison chart of simulation results and analytical solutions;

[0095] Figure 12 A diagram showing the influence of geostress on bedding strength and three typical crack shapes;

[0096] Figure 13 This is a grey relational diagram showing the relationship between the fracturability index and influencing factors.

[0097] Figure 14 This is a schematic diagram showing the development location of the dominant stratiform group and the development segment in Block A. Detailed Implementation

[0098] The present invention will be further defined below with reference to the accompanying drawings and embodiments, but is not limited thereto.

[0099] Terminology Explanation:

[0100] 1. TOC (Total Organic Carbon) is an important parameter characterizing the abundance of organic matter in shale. It is expressed as a percentage of rock mass to represent the abundance of organic matter.

[0101] 2. XRD analysis: Shale minerals are mainly composed of quartz, feldspar, clay minerals, carbonate rocks, pyrite, and other minerals. X-ray diffraction (XRD) is mainly used for whole-rock mineral composition analysis of shale.

[0102] 3. Brazilian Splitting Test: The Brazilian Splitting Test is a standard test method for determining the tensile strength of brittle materials. Also known as the Brazilian disc splitting test, it is a widely used method in rock mechanics and engineering, primarily used to measure mechanical parameters such as tensile strength, elastic modulus, and fracture toughness of rocks.

[0103] 4. The triaxial compression test is the most important and core indoor mechanical testing method in rock mechanics because it can most realistically simulate the stress state of rocks deep underground.

[0104] Limitations of uniaxial tests: Uniaxial tests (axial pressure in only one direction) cannot simulate the triaxial stress state of rocks in the formation (compression from overlying strata and surrounding strata).

[0105] The advantage of triaxial testing is that it simulates the lateral constraints on underground rocks by applying a confining pressure to a cylindrical rock sample, thus enabling the testing of the mechanical behavior of rocks in a more realistic underground environment.

[0106] Obtain key rock strength parameters:

[0107] Cohesion: Represents the initial bond strength between rock particles, and is the part of shear strength that is independent of normal stress.

[0108] Internal friction angle: represents the resistance to sliding friction between rock particles after being subjected to force. This resistance increases with the increase of normal stress.

[0109] In engineering, cohesion and internal friction angle are more important than a single "compressive strength" value because they can be used to calculate the rock strength under any stress state.

[0110] Triaxial compression testing, by simulating real underground stress environments, provides us with two fundamental parameters describing the intrinsic shear strength characteristics of rocks: cohesion and internal friction angle. It serves as a bridge connecting laboratory core data with field engineering design and decision-making, and is the gold standard testing method in the field of rock mechanics.

[0111] 5. Tensile Strength: Tensile strength is one of the key mechanical properties of shale. Tensile strength refers to the maximum ability of a material to resist fracture when subjected to uniaxial tensile stress. Simply put, it is the maximum force required to "break" it.

[0112] 6. Compressive strength: The compressive strength of shale is its ability to resist failure when subjected to uniaxial or triaxial compressive stress. This is one of the most critical parameters for evaluating the mechanical properties of shale, and it is especially important in oil and gas reservoir development and geological engineering.

[0113] 7. Elastic modulus: The elastic modulus of shale is the ratio of stress to strain during the elastic deformation stage, characterizing its ability to resist elastic deformation. It is significantly influenced by mineral composition, pore structure, organic matter content, and bedding orientation, and exhibits anisotropic characteristics. In shale gas development, it is used to assess reservoir brittleness and fracturing effectiveness.

[0114] The elastic modulus of shale is defined as the ratio of stress (σ) to strain (ε) (E = σ / ε), reflecting the stiffness of shale against deformation within its elastic range. The larger this value, the less prone the shale is to elastic deformation, and the higher its stiffness. Since the stress-strain curve of shale is often nonlinear, it needs to be characterized using the tangent or secant elastic modulus.

[0115] 8. Poisson's ratio of rock is a core parameter characterizing the elastic deformation properties of rock. It is defined as the ratio of the absolute values ​​of transverse strain to axial strain when subjected to axial compression.

[0116] 9. The brittleness index is a key indicator for assessing the ease with which rocks fracture during hydraulic fracturing. A higher brittleness index means that the rock is more prone to fracture, which not only improves fracturing efficiency but also increases production.

[0117] The Young's modulus and Poisson's ratio of the studied layer were normalized to fall between 0 and 1.

[0118] E_norm = (E - E_min) / (E_max - E_min)

[0119] ν_norm = (ν_max - ν) / (ν_max - ν_min)

[0120] Note that the larger Young's modulus is, the more brittle it is, so it is a positive normalization; the smaller Poisson's ratio is, the more brittle it is, so it is a negative normalization.

[0121] Take the average of the two normalized parameters:

[0122] BI_elastic = (E_norm + ν_norm) / 2.

[0123] The pseudo-triaxial test, also known as the conventional triaxial test, is characterized by the equality of the two principal stresses (i.e., σ1 > σ2 = σ3, maximum principal stress > intermediate principal stress = minimum principal stress). Simply put, in engineering practice and most scientific research, when people mention "triaxial test," they are implicitly referring to the "pseudo-triaxial test" (i.e., the conventional triaxial test). It represents the optimal balance between simulating real formation stress states and achieving engineering feasibility under current technological conditions.

[0124] Example 1

[0125] A reservoir compressibility evaluation method considering shale lamination development characteristics includes:

[0126] Step 1: Experimental study on the influence of shale lamination development characteristics on mechanical properties: Based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes were designed for shale lamination development characteristics, and the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamination combinations were analyzed.

[0127] Step 2: Study on the influence of shale lamination on tensile properties: By conducting Brazilian splitting tests on shale with different lamination groups, the differences in crack propagation modes and fracture ultimate loads are studied. Then, the fluctuation of the stress-strain curve after the peak value is used to study the complexity of crack propagation. A correlation chart between relevant parameters of shale lamination structure and fracture toughness is established, and the influence of shale lamination on tensile properties is comprehensively analyzed.

[0128] Step 3: Study on the influence of shale laminae on compressive properties: Pseudo-triaxial tests were conducted on shale with different laminae to observe the differences in artificial crack propagation morphology. Different confining pressure conditions were designed to obtain the ultimate fracture load of shale with different laminae. The brittleness index calculated by Young's modulus and Poisson's ratio obtained from rock mechanics tests was used to characterize shale brittleness. The influence of laminae composition on reservoir brittleness was analyzed, and the influence of shale laminae on compressive properties was comprehensively analyzed.

[0129] Step 4: Consider the longitudinal pressure fracture network penetrating the layer physical simulation experiment of the layer stress barrier zone: use artificial layered rock samples to simulate the pressure fracturing test, and use the true triaxial loading method to restore the relative magnitude of the triaxial principal stress of the formation. Each sub-layer is cast with pure cement and different proportions of quartz sand or soil to make different physical and mechanical parameters. Design different tests to study the law of crack propagation under different interlayer physical property parameter comparisons.

[0130] Step 5: Considering the longitudinal pressure fracture network penetrating the layer with the layer stress barrier: Based on the cohesive finite element method, the interaction mechanism between hydraulic fractures and bedding planes is studied, and the influence of vertical stress and interface strength on the penetrating behavior of hydraulic fractures is revealed.

[0131] Step 6: Study on the influence of lamination development characteristics on hydraulic fracture penetration behavior: Based on the results of physical simulation experiments and finite element numerical simulations, the influence of interlayer stress difference, layer interface properties, and vertical stress caused by lamination on the fracture propagation behavior at the interlayer interface is analyzed; laying a theoretical foundation for reservoir compressibility evaluation.

[0132] Step 7: Establish evaluation indexes for the fracturability of shale reservoirs: Based on the key factors affecting reservoir fracturability identified in the research, and considering the control effect of key factors on the fracturability of shale reservoirs, establish evaluation parameters for shale fracturability, and then normalize them to the same standard using the range standardization method. For indices that are affected by multiple factors, multiplication and division of different factors are used to integrate their mutual influence.

[0133] Step 8: Evaluation of the distribution location of the dominant lamellar combination in the target block and the reservoir compressibility: Based on the compressibility characteristics, combined with the distribution of high-quality lamellars, reservoir physical properties, mechanical properties and compressibility, a lamellar iron pillar is established to clarify the distribution location of the dominant lamellar combination in the target block and the reservoir compressibility.

[0134] Example 2

[0135] The difference between this method and the reservoir compressibility evaluation method considering shale lamination development characteristics described in Example 1 is that:

[0136] Step 1, experimental study on the influence of shale lamination characteristics on mechanical properties: Based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes were designed for shale lamination characteristics to analyze the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamination combinations; details are as follows:

[0137] For the selected target shale block, mechanical parameters were obtained under different lamellar combinations through indoor and outdoor sampling. The following example uses block A:

[0138] XRD analysis, as detailed below:

[0139] Mineral composition analysis was performed using an automated X-ray diffractometer with an accuracy of 0.001°. The scanning angle was set to 3°≤2θ≤80°, and the scanning speed was 2° / min. After the test, semi-quantitative mineral composition analysis was completed through data processing. For sample testing, the diffraction parameters were set as follows: 2θ angle measurement range 3°-70°, step size 0.02°, and dwell time per step 0.4s. The obtained experimental data were processed using DIFFRAC.EVA software to complete the quantitative analysis of mineral components, thereby obtaining the contents of quartz, feldspar (potassium feldspar, sodium feldspar), clay minerals (kaolinite, illite, chlorite, etc.), carbonate minerals (calcite, dolomite), and pyrite. The test results are shown in Table 1.

[0140] The TOC test, as detailed below:

[0141] The TOC of the samples was determined using a carbon-sulfur analyzer. Before the TOC test, the sample powder needed to be acid-treated. 0.1 g of 200-mesh sample powder was placed in a permeation crucible, and a 5% (w / w) hydrochloric acid solution was prepared. The prepared dilute hydrochloric acid was added to the permeation crucible until the liquid level was slightly below the crucible's edge, fully dissolving the inorganic carbon in the sample. The crucible was then placed on a crucible rack. This process was repeated 6 times after all the dilute hydrochloric acid solution had seeped out of the permeation crucible. Hydrochloric acid residue remained in the acid-treated sample powder and the permeation crucible, so it needed to be cleaned with deionized water. Deionized water was added to the permeation crucible until the liquid level was flush with the crucible's edge. This process was repeated 6 times after all the deionized water had seeped out to ensure complete removal of residual hydrochloric acid. The treated sample was placed in a drying oven and dried continuously at 80°C for 48 hours to ensure the sample was dry. The permeation crucible containing the dried sample was removed and cooled to room temperature. A combustion accelerant was then added, and finally, the sample was placed on the instrument's lifting platform for the TOC determination experiment. The test results are shown in Table 1.

[0142] The Brazilian splitting test, as detailed below:

[0143] The tensile strength test was conducted using the Brazilian disc splitting test method. Shale specimens perpendicular to the striations were fabricated into 20×10mm discs and fixed between the pressure plates of the testing equipment. A 2mm diameter steel wire was placed between the pressure plates as a spacer. Applying pressure caused the specimen to fracture radially, resulting in tensile failure. The loading stress at which splitting occurred was determined to be P. t The formula for calculating tensile strength is:

[0144] ;

[0145] In the formula, D represents the diameter of the cylindrical sample (mm); δ represents the sample thickness (m); P t The applied stress is the stress at which the specimen splits.

[0146] The test results are shown in Table 1.

[0147] The triaxial compression test is as follows:

[0148] In the pseudo-triaxial test, a shale sample perpendicular to the laminae was prepared into a cylindrical rock sample with a diameter of 25 mm and a height of 50 mm and placed in a pressure chamber. A lateral loading system, via a pressure booster, injected a constant amount of working oil into the pressure chamber to provide confining pressure to the sample. The confining pressure was gradually increased to a certain value, and after it stabilized, an axial loading system applied a gradual load to the specimen through a force transmission rod until macroscopic failure of the rock occurred. Based on the rock failure load, axial deformation, and radial deformation automatically recorded by the testing instrument, axial stress, axial strain, and radial strain can be obtained, allowing the plotting of the stress-strain curve for the triaxial test. The required rock mechanical parameters (including static elastic modulus, static Poisson's ratio, etc.) can be calculated from the stress-strain curve. The test results are shown in Table 1.

[0149] Table 1. Mechanical property parameters of shale under different lamination types in Block A;

[0150]

[0151] The specific implementation process of step 2 includes:

[0152] Analysis of Brazilian splitting tests on shale with different lamellar groups revealed significant differences in crack propagation modes and ultimate fracture loads under tensile stress. Based on crack propagation morphology, samples were categorized into central vertical cracks, eccentric arc-shaped cracks, and branching cracks. Central vertical cracks represent pure tensile failure with a single crack propagation mode, and samples exhibiting this failure mode have the highest ultimate fracture load. Samples with eccentric arc-shaped cracks have lower ultimate fracture loads than those with central vertical cracks, while samples with branching cracks have the lowest ultimate fracture loads. Specifically, samples with graded thin silt-thick mud lamellar combinations and graded medium-thick silt-mud lamellar combinations primarily exhibited eccentric arc-shaped cracks and branching cracks.

[0153] According to the Brazilian splitting stress-strain curve, ( Figure 1 The tensile stress-strain curves before the peak value obtained from the Brazilian splitting test show obvious fluctuations, indicating the presence of weak bedding planes or numerous microcracks in the samples. The continuous propagation and closure of these cracks lead to stress fluctuations. The fluctuations in the tensile stress-strain curves after the peak value reflect the complexity of crack propagation in the samples. The graded thin silt-thick mudstone layer and graded medium-thick silt-mudstone layer composite samples have relatively low ultimate fracture loads, while the massive layered shale composite has the highest.

[0154] Fracture toughness is a measure of a material's resistance to crack propagation and is an inherent property of the material. A higher fracture toughness value is less conducive to hydraulic fracturing. Based on fracture morphology, fracture toughness is classified into three types: Type I (opening), Type II (staggered), and Type III (tearing). It is generally believed that hydraulic fracturing produces mostly Type I cracks; therefore, the empirical formula for Type I fracture toughness is used for calculation.

[0155] ;

[0156] In the formula, K 1c For type I fracture toughness, P max B is the maximum destructive load value of the Brazilian splitting fracture, kN; B is the sample thickness, cm; D is the diameter, cm. It is the stress intensity factor; according to ISRM (1995), its value is 0.84.

[0157] Establish a graph showing the correlation between shale lamellar structure parameters and fracture toughness. Figure 2 and Figure 3 ); Figure 2 and Figure 3 Shale plunger samples from three wells, L203H153-8, N213, and Y206, with different degrees of lamination development (characterized by "lamination density (strips / mm)" and "lamination thickness (mm)"), were selected. Correlation tests were conducted, and then correlation maps were generated.

[0158] The results show that lamination structure has a significant impact on the tensile properties of shale. The average density of the lamination set shows a strong negative correlation with fracture toughness, while the average thickness of the lamination set shows a strong positive correlation with fracture toughness. This is mainly because crack propagation follows the principle of minimum energy consumption; well-developed laminations create mechanically weak surfaces at the lamination interfaces, which is conducive to crack propagation. The average thickness of the lamination set also shows a strong positive correlation with fracture toughness. Thicker lamination assemblages, especially alternating thick silt laminations and thin mud laminations, result in a denser reservoir due to the more ordered arrangement of minerals. The excessive silt particles also increase the energy consumption for fracture propagation, leading to increased fracture toughness.

[0159] The specific implementation process of step 3 includes:

[0160] Step 3.1: Conduct pseudo-triaxial tests on shale with different lamellar groups to observe and clarify the differences in artificial crack propagation morphology in shale with different lamellar combinations;

[0161] Due to the varying depths of the Wufeng-Longmaxi Formation shale in the three wells, the confining pressures also differ. To more accurately determine the compressive strength of the target strata, pseudo-triaxial tests were conducted on shale samples from Block A under confining pressures of 80 MPa, 45 MPa, and 55 MPa. The artificial crack propagation morphology of shale samples with different lamellar combinations showed significant differences. In the interbedded thick silt-thin mud lamellar combination shale samples, the silt and mud layers had straight, clear interfaces with good continuity, easily leading to stress concentration. The massive type mainly formed a single fracture network structure, with a simple crack propagation mode. In the graded lamellar combination samples, the microstructural surfaces at the lamellar interfaces did not show obvious mineral differentiation, making stress less likely to concentrate. This resulted in a complex fracture network structure dominated by oblique shear fractures and horizontal shear fractures along the lamellar surfaces. The complexity of the fracture network increased sequentially among the thick mud lamellar combination, the thick silt-thin mud lamellar combination, the medium-thick silt-thin mud lamellar combination, and the thin silt-thin mud lamellar combination.

[0162] Step 3.2: Design different confining pressure conditions to obtain different shale fracture ultimate loads with different laminar combinations; the shale fracture ultimate load is a commonly used experiment in rock mechanics.

[0163] Three confining pressure conditions were applied to three wells in triaxial compression tests to obtain the relevant mechanical properties of the rock strata under formation conditions. The characteristics of the obtained stress-strain curves are as follows: Figure 4According to the triaxial stress-strain curves, after the stress reaches the peak stress, the deformation continues to increase with the continuation of loading, transitioning to ductile-brittle failure characteristics. The increase in confining pressure also leads to a transition from predominantly elastic deformation to localized elastoplastic deformation. Before reaching the peak stress, stress drops often occur, reflecting the nonlinear mechanical behavior of shale during loading. The development of laminae and fractures increases the probability of nonlinear mechanical behavior in shale. The fracture ultimate load is relatively small for graded thin silt-thick mud laminae and medium-thick silt-mud laminae composite samples, while the fracture ultimate load is relatively large for massive and interbedded laminae composite shale samples.

[0164] Step 3.3: Based on the experimental results (i.e., the Poisson's ratio and elastic modulus were tested on samples with different texture combinations), compare the characteristics of the elastic modulus (Young's modulus) and Poisson's ratio of different texture groups;

[0165] The lamellar groups corresponding to the elastic modulus from large to small are as follows: the overall pattern is a graded thin silt-thick mud lamellar combination, a graded thick silt-thick mud lamellar combination, a graded medium-thick silt-mud lamellar combination, an interbedded thick silt-thick mud lamellar combination, a graded thick mud lamellar combination, and a massive lamellar combination shale.

[0166] The laminar sets corresponding to Poisson's ratio from smallest to largest are as follows: graded thin silt-thick mud laminar set, graded medium-thick silt-mud laminar set, graded thick silt-thin mud laminar set, interbedded thick silt-thin mud laminar set, massive laminar set, and graded thick mud laminar set shale trends; such as... Figure 5 As shown, the good regularity trend of lamination assemblage with Poisson's ratio and elastic modulus indicates that sedimentary structure is the main influencing factor of lamination on rock mechanical properties. Gradual-type thin silt-thick mud and medium-thick silt-mud lamination assemblage shale have relatively large elastic modulus and small Poisson's ratio, and good brittleness.

[0167] Step 3.4: Evaluate the influence of laminar composition on reservoir brittleness. The brittleness index is calculated using Rickman's method, which uses Young's modulus and Poisson's ratio obtained from rock mechanics tests to characterize shale brittleness. As shown below:

[0168] ;

[0169] ;

[0170] ;

[0171] Where YM represents the static Young's modulus, GPa; YM max Represents the maximum static Young's modulus, GPa; YM minRepresents the minimum static Young's modulus, GPa; YM Brit PR represents the normalized Young's modulus, 0~1; PR represents the static Poisson's ratio, dimensionless; PR max Represents the maximum static Poisson's ratio, dimensionless; PR min Represents the minimum static Poisson's ratio, dimensionless; PR Brit Represents the normalized static Poisson ratio, 0~1;

[0172] Establish a table showing the relationship between mineral composition and brittleness index ( Figure 6 , Figure 7 and Figure 8 That is, select shale samples with different mineral compositions (i.e., different compositions of silica, clay minerals, and calcium), calculate the corresponding brittleness index, and then establish a table showing the relationship between mineral composition and brittleness index;

[0173] Statistical results show that the content of siliceous minerals and the brittleness index of the samples are significantly positively correlated, indicating that the laminar composition has a significant impact on reservoir brittleness.

[0174] The specific implementation process of step 4 is as follows:

[0175] 1. Test methods and sample preparation;

[0176] Indoor hydraulic fracturing tests were conducted using either natural or artificial rock samples. Due to limitations in the availability and processing conditions of natural rock samples, concrete samples were used to simulate the fracturing test. Because the true triaxial test frame applies pressure to the sample using a rigid pressure plate, the parallelism of the sample end faces is critical, with a non-parallelism generally not exceeding 0.01 mm. Specialized molds were used for fabrication.

[0177] The specimens were cast using pure cement and cement with varying proportions of quartz sand or clay. Each specimen was a 300mm cube. Simultaneously, a steel pipe with an outer diameter of 10mm, an inner diameter of 6mm, and a length of 130mm was pre-placed within the specimen as a simulated wellbore. A specially made 50mm long cardboard tube was attached to the lower part of the steel pipe to form an open-hole section in the center of the specimen after solidification. During simulated fracturing, due to the lower strength of this section, initial fractures would form in this section. The dimensions and structure of the cast specimen are as follows. Figure 8 As shown.

[0178] Conduct simulated fracturing tests, including:

[0179] The first step is to simulate the layered medium. This stratified medium hydraulic fracturing physical simulation experiment uses artificially layered rock samples for simulated fracturing tests, and concrete samples are also processed using specialized molds. The upper and lower partitions of the sample are cast from cement and quartz sand, with sand added according to a predetermined ratio (by weight). The cement grade is 425 building cement, and the sand is fine sand. The intermediate production layer of the sample is cast from a mixture of cement and sand, and several sets of experiments are conducted. The cement-sand mixing ratio can be 1:2, 1:1, 1:3 (by weight), etc. (which can be adjusted intentionally). The cement grade is 425 building cement, and the sand is sieved fine river sand. Because the cement and sand ratios used in each layer are different, the simulated upper and lower partitions and intermediate production layer are created, resulting in differences in the materials of each layer. This intentionally creates differences in the physical properties of each layer (such as permeability, elastic modulus (E), fracture toughness (G), etc.) to verify the influence of the differences in the mechanical properties of the partitions and production layers on the crack propagation mechanism and crack arrest effect.

[0180] The second step is to conduct layered in-situ stress simulation. Hydraulic fracturing simulation tests require simulating formation conditions, one of the most important factors being the magnitude and distribution of formation stress. Generally, the three principal stresses of a formation are not equal, and the magnitude of the horizontal stress varies across different layers. For hydraulic fracturing, the relative magnitudes of the three principal stresses determine the direction of fracture propagation, while the magnitude and distribution of the minimum horizontal stress affect the fracture geometry. Figure 10 This is a geometric model diagram. The true triaxial loading method used in the simulation experiment better reflects the actual stress state of the formation. The test frame uses flat jacks to apply rigid loads to the sides of the specimen. Based on the characteristics of hydraulic fracturing, three pairs of flat jacks are used in one horizontal direction to simulate the in-situ stress of the producing layer and the upper and lower diaphragms, respectively. One pair of flat jacks is placed in each of the other two directions to simulate vertical and maximum horizontal in-situ stress. Hydraulic pressure is supplied to the flat jacks by a multi-channel pressure stabilizing source, and the pressure of each channel can be controlled independently (the maximum supply pressure of each channel can reach 60 MPa). In this way, by applying different pressures to each layer of medium, the effect of stratified in-situ stress simulation is achieved. Simultaneously, the true triaxial loading method is used to artificially control the fracture extension direction, making the test specimen as close as possible to the stress state of the actual oil layer.

[0181] The third step is to simulate the interlayer mechanical differences; each sublayer is cast using pure cement and different proportions of quartz sand or clay, resulting in different physical and mechanical parameters; the differences in elastic modulus corresponding to different sand and cement ratios are shown in Table 2 below:

[0182] Table 2 Elastic modulus of different sand-to-mud ratios;

[0183]

[0184] The fourth step is to simulate the interface strength. During the layered casting process, different interface strengths are simulated by varying the time interval between the two layers.

[0185] 2. Test Procedure

[0186] After placing the sample into the press, the pressure plate and other components of the press are installed. To ensure uniform loading of the pressure plate onto the sample surface, a rubber gasket is placed between the pressure plate and the sample. After the sample is installed, a triaxial confining pressure is applied by a hydraulic pressure stabilizing source; then, fracturing fluid is pumped into the simulated wellbore according to the selected pump displacement until the sample fractures. After the sample fractures, the fracture morphology and the traces of fracturing fluid on the fracture surface are observed. Parameters such as pumping pressure and displacement during fracture propagation are recorded using an MTS testing machine.

[0187] 3. Experimental Results and Analysis

[0188] The study investigated the effects of differences in elastic modulus, interfacial bonding strength, and interlayer stress.

[0189] The effect of differences in elastic modulus includes:

[0190] Four sets of experiments were designed to discuss the crack propagation law under different interlayer physical property parameter comparisons. The main purpose was to study the influence of the difference in elastic modulus on whether the crack can pass through the interlayer interface and enter the interlayer; as shown in Table 3.

[0191] Table 3 Experimental Scheme;

[0192]

[0193] Experimental results: Sample 1-1: High vertical stress (6MPa), high modulus of the intermediate layer, cracks easily penetrated; Sample 1-2: High vertical stress (6MPa), modulus of the intermediate layer was similar to that of the upper and lower layers, cracks penetrated the upper and lower sub-layers; Sample 1-3: High vertical stress (6MPa), low modulus of the intermediate layer, cracks penetrated the upper and lower sub-layers; Sample 1-4: High vertical stress (0.3MPa), low modulus of the intermediate layer, cracks penetrated the upper and lower sub-layers. The main reason is the short interval between pouring layers and the interface bonding strength. This indicates that when the interface strength is high, the difference in elastic modulus has a smaller effect on preventing cracks.

[0194] To better illustrate the influence of elastic modulus, a well-cemented two-layered medium was established, and the effect of the elastic model on the propagation of hydraulic fractures through the layer was discussed. Numerical simulation results show that, under well-cemented interfacial conditions, the interfacial layer with a high elastic modulus does not significantly restrict fracture propagation through the interface; on the contrary, it promotes an increase in fracture height within the interfacial layer, specifically manifested as a larger fracture height and a smaller fracture width (making sand addition difficult). Initially, when encountering a high-modulus interfacial layer, the high elastic modulus of the interfacial layer has an hindering effect. However, due to the high cementation strength and the pressure buildup within the fracture (high construction pressure), it will eventually break through the interfacial layer. Once inside the interfacial layer, the fracture height increases sharply due to the conservation of fracturing fluid volume, as the modulus decreases with increasing fracture width.

[0195] Influence of interfacial bonding strength; including:

[0196] Several sets of experiments were designed (3 sets of experiments were designed), with all layers of the specimen having the same composition; the differences were in the properties of the interlayer interfaces, the fracturing fluid used in the experiments, the experimental loading rate, and the magnitude of the pressure on the interfaces; the purpose of the experiments was to discuss and study the influence of different interface properties, interface stress conditions, and experimental loading rates on the crack morphology for the same specimen; as shown in Table 4:

[0197] Table 4 Experimental Scheme;

[0198]

[0199] Experimental results show that: Sample 2-1: The crack deflects after reaching the interlayer interface and propagates entirely along the interlayer interface, without fully propagating in the intermediate layer; Sample 2-2: A vertical crack exists in the intermediate layer, the interlayer interface slips, and fracturing fluid is present on the cemented surface; Sample 2-3: A vertical crack propagates only in the intermediate layer, with no fracturing fluid infiltrating the cemented surface, indicating that it does not extend to the upper or lower layers and does not form a horizontal crack. The results indicate that interlayer cementation strength and vertical stress have a significant impact. When the interface itself has low strength, even with high overburden pressure, after the crack propagates to the interlayer interface, it will often slip along the interface (Sample 2-2) or completely deflect and propagate along the interlayer interface (Sample 2-1). In this case, the difference in physical properties between the upper and lower interlayers has a weaker impact. When the interlayer interface is not cemented: hydraulic cracks extend along the interlayer, and the rock remains intact without damage; when the interlayer interface is weakly cemented: cracks first start from the rock with the weakest tensile strength, and when the cracks extend to the weakly cemented surface, the hydraulic cracks change direction and extend along the weakly cemented surface; when the interlayer is well cemented: the rock fractures sequentially in each rock sample, eventually resulting in overall failure.

[0200] The effects of interlayer stress differences include:

[0201] The three cement blocks below were cast from the same material in a single pour, without any material separation; however, they were subjected to layered loading to verify the model above. (Since the differences in physical properties between the producing layer and the interlayer are not considered for the time being, it is assumed that the physical properties of the producing layer and the interlayer are the same, and only the influence of the difference in their effective stress on crack propagation is considered). As shown in Table 5:

[0202] Table 5 Experimental Scheme;

[0203]

[0204] Experimental results: Under a lower stress of 6 MPa, the fracture in specimen 1-1 propagated upwards; under a lower stress of 4 MPa, specimen 1-2 partially connected the upper and lower layers, and due to the wellbore influence, propagated upwards more significantly; specimen 1-3, under a lower stress of 2 MPa, could not prevent fracture propagation. The results indicate that interlayer stress (minimum horizontal stress) has a significant impact on fracture penetration; the critical interlayer stress difference hindering fracture penetration is 4-6 MPa.

[0205] The crack propagation pattern under different interlayer stress differences shows that, in general, when the interlayer stress difference is greater than 4 MPa, it is difficult for pressure cracks to penetrate longitudinally.

[0206] The specific implementation process of step 5 includes:

[0207] Research methods and model establishment:

[0208] Based on the cohesive finite element method, this study investigates the interaction mechanism between hydraulic fractures and bedding planes, revealing the influence of vertical stress and interfacial strength on the cross-layer behavior of hydraulic fractures. In the model, the initiation and propagation process of hydraulic fractures is described using stiffness damage, the frictional behavior of the bedding planes satisfies Coulomb's law of friction, rock deformation satisfies equilibrium equations, and the fluid within the fracture obeys the cubic law. The computational model is a laboratory-scale two-layer medium, with two pre-fabricated orthogonal fractures defining the propagation path, such as... Figure 8 As shown. The model is symmetrical about the xoz plane, with the plane containing the injection point being the symmetrical boundary, and the other five planes being the displacement boundaries.

[0209] Parameter settings:

[0210] To reduce the impact of model scale and parameter dimensions, the two influencing parameters, geostress and bedding strength, are treated as dimensionless, and the vertical stress difference coefficient is defined as:

[0211] ;

[0212] In the formula, —Vertical stress difference coefficient, dimensionless; —Minimum horizontal ground stress, ; —Vertical stress, .

[0213] To quantitatively characterize the influence of bedding planes on tensile and shear strength, a dimensionless composite bedding strength is defined by the relative magnitudes of the tensile strength of the bedding planes and the underlying rock strata, as well as the cohesion in the two tangential directions:

[0214] ;

[0215] In the formula, —Lamination tensile strength, ; —Tensile strength of the lower rock strata, ; -index, ; — Cohesive forces along the first or second tangential direction of the bedding plane; —The cohesive force in the first or second tangential direction of the lower rock strata;

[0216] Since the model size is laboratory-scale and the fracturing time is very short, the filtration process of fracturing fluid can be ignored. The simulation parameters are based on the experimental parameters mentioned above; the fracturing fluid injection rate is 6 in all examples. The viscosity is 200. The specific parameters are shown in Table 6.

[0217] Table 6 Simulation parameters;

[0218]

[0219] Simulation results and analysis:

[0220] Before conducting hydraulic fracturing simulations of layered shale, a benchmark model was used to verify the model's feasibility. The model validation problem was the propagation of a single disk-shaped hydraulic fracture under viscosity-dominant conditions, without considering filtration loss. The simulation results were compared with the analytical solutions proposed by Savitski and Detournay. The comparison results showed that ( Figure 11 Except for minor differences near the slit tip, the numerical and analytical solutions are in good agreement, verifying the effectiveness and accuracy of the model. Figure 11 In the figure, (a) shows the variation of net pressure within the crack, and (b) shows the variation of crack width.

[0221] By continuously adjusting the tensile strength, cohesion, and vertical stress of the bedding planes, the vertical cross-bedding propagation law of hydraulic fractures under different vertical stress difference coefficients and bedding plane strengths was studied. After the simulation, based on the different interaction modes between the hydraulic fractures and the bedding planes, three typical fracture morphologies were exhibited: T-shaped fractures, passivated fractures accompanied by bedding slip, and cross-bedding fractures penetrating the bedding planes. The lower the interface strength and the smaller the vertical stress difference coefficient, the easier it is to form T-shaped fractures; the lower the interface strength and the larger the vertical stress difference coefficient, the easier it is to form passivated fractures (deep shale); the higher the interface strength and the larger the vertical stress difference coefficient, the easier it is to form cross-bedding fractures.

[0222] Based on the numerical simulation results under different conditions of bedding plane strength and vertical stress difference coefficient, the following diagram is drawn: Figure 12 The integrated control map shown is divided into three sub-regions based on three typical fracture morphologies: the lower left region is the T-type fracture control region; the upper left region is the passivation fracture control region; and the upper right region is the cross-layer fracture control region. The results indicate that lower bedding plane strength and smaller vertical stress difference coefficients make T-type fractures more likely to form; lower bedding plane strength and larger vertical stress difference coefficients make passivation fractures more likely to form; and higher bedding plane strength and larger vertical stress difference coefficients make cross-layer fractures more likely to form. Indoor rock mechanics tests show that the vertical stress difference coefficient of medium-deep shale reservoirs is 0.03–0.16, and the dimensionless bedding strength is 0.25–0.46, mainly forming cross-layer fractures; the vertical stress difference coefficient of deep shale is 0.18–0.35, and the dimensionless bedding strength is 0.03–0.16, indicating shear fracture of the bedding planes, mainly forming passivation fractures.

[0223] Because the deep shale in the Sichuan Basin is not deeply buried and has a small vertical stress difference coefficient, but has been subjected to less tectonic compression during the post-depositional period, the cementation of bedding planes and natural fractures is high. Therefore, even under relatively low vertical stress difference coefficients, hydraulic fractures can penetrate bedding planes, resulting in large fracture heights and ultimately forming a fishbone-like fracture network dominated by transverse fractures. Deep shale reservoirs are deeply buried and have a large vertical stress difference coefficient, but have been subjected to significant tectonic compression during the post-depositional period. This leads to extremely low cementation strength of weak structural surfaces such as bedding planes and natural fractures, much lower than that of medium-deep shale. Therefore, even under high vertical stress difference coefficients, hydraulic fractures cannot penetrate these weak structural surfaces, resulting in small fracture heights and ultimately forming a multi-lateral step-like fracture network dominated by horizontal fractures.

[0224] The specific implementation process of step 6 includes:

[0225] Based on the above physical simulation and finite element simulation results, it is evident that the interlayer stress difference, the properties of the layer interface, and the vertical stress have a crucial impact on the propagation behavior of fractures at the interlayer interface. Whether a fracture can penetrate the interlayer interface and enter a layer mainly depends on the relative magnitudes of these three factors. Therefore, the influence of laminar development characteristics on these three parameters is key to evaluating reservoir compressibility.

[0226] To clarify the influence of laminae and reservoirs on fracturability, the grey relational analysis method was used to evaluate and rank the influencing factors of the fracturability index. The grey relational analysis method is used to characterize the correlation between the magnitude, direction, and rate of change of various factors in the data. If the relative changes are relatively consistent, the correlation coefficient is high, and vice versa. Figure 13 The grey relational diagram shows the relationship between the fracturability index and influencing factors; the specific analysis includes the following steps:

[0227] A reference sequence was determined; in this study, the fracturability index (F) was used as the reference sequence.

[0228] Dimensionlessize all sequences;

[0229] The correlation coefficient C is calculated using the following formula;

[0230] ;

[0231] in, It is the minimum absolute difference between the reference sequence and the subsequence. ρ is the maximum absolute difference between the reference sequence and the subsequence, ρ is the resolution coefficient, which is a fixed value of 0.5 in traditional grey relational analysis, and X is the absolute difference between each value of the reference sequence and the subsequence.

[0232] The correlation coefficients between the subsequence and the reference sequence are averaged to obtain the correlation between the reference sequence and a certain subsequence.

[0233] Sort according to the correlation between the reference sequence and the subsequence.

[0234] The grey relational value ranges from 0 to 1. A higher value indicates a stronger correlation with the "reference value" (parent sequence), meaning a higher evaluation. Figure 11 It can be seen that TOC (0.93), lamellar assemblage type (0.921), and siliceous mineral content (0.916) are the main factors affecting the fracturability of shale, followed by the average thickness of lamellar assemblage and the density of mud lamellar layers.

[0235] The specific implementation process of step 7 includes:

[0236] The fracturability of shale reservoirs cannot be fully determined solely by brittleness or elastic modulus and Poisson's ratio. A comprehensive assessment is needed, considering the influence of brittleness (representing the ease of fracturing and reflecting the complexity of fractures formed after fracturing), fracture toughness (representing the ease of fracturing and reflecting the ability of the reservoir to maintain fracture extension after fracturing), and compressive strength (representing the rock's resistance to permanent deformation and fracture, reflecting the factors that determine whether fractures can form under compressive stress) on the fracturability of shale reservoirs. Therefore, three parameters—brittleness index, fracture toughness, and compressive strength—considering lamination characteristics, are used to evaluate shale fracturability.

[0237] Different parameters have varying effects on fracturability. Higher brittleness makes fine-grained sedimentary rocks more prone to fracture; higher fracture toughness makes it harder for cracks to extend; and higher compressive strength increases the rock's resistance to permanent deformation and fracture, making it less susceptible to fracturing and the formation of complex cracks. Therefore, the fracturability of fine-grained sedimentary rocks is positively correlated with the brittleness index and negatively correlated with fracture toughness and compressive strength. In other words, the brittleness index is a positive indicator, while fracture toughness and triaxial compressive strength are negative indicators. Furthermore, due to significant differences in the units and values ​​of different influencing factors, a range standardization method is used to normalize them to a common standard.

[0238] ;

[0239] ;

[0240] In the formula, Y represents the positive standardized value of the indicator; Y1 represents the negative standardized value of the indicator; and X represents the normal value of the indicator. The maximum value of the characterization index X; The minimum value of the characterization index X;

[0241] For indicators influenced by multiple factors, the mutual influence can be synthesized by multiplying or dividing the different factors. By multiplying and dividing the three normalized indicators, a fracturability index (the ease of fracturing, with a higher value indicating easier fracturing) can be established by combining the static brittleness index, fracture toughness, and triaxial compressive strength under confining pressure conditions.

[0242] ;

[0243] In the formula, F is the fracturability index, which is dimensionless; B is the static brittleness index after positive normalization, which is dimensionless; K is the fracture toughness after negative normalization, which is dimensionless; and σ is the triaxial compressive strength after negative normalization, which is dimensionless.

[0244] The specific implementation process of step 8 includes:

[0245] Based on the aforementioned research results, and combined with the distribution of high-quality laminae, reservoir properties, mechanical properties, and fracturing capability, a laminae iron column model for Block A was established. Figure 14 This study clarifies the development characteristics and distribution location of high-quality laminae and the compressibility of reservoirs.

[0246] High-quality shale laminae in Block A are mainly developed in the lower part of the 2nd sublayer and the middle and lower part of the 6th sublayer. Taking well 01 as an example, they are mainly distributed at the positions of 4113~4115m in the 2nd sublayer and 4072.6~4075.0m in the 6th sublayer. Figure 12 The main developmental characteristics of its high-quality lamellar segments are as follows:

[0247] The two high-quality shale layers are characterized by a graded combination of thin silt and thick mudstone bedding; the residual organic carbon (TOC) is high, at 4%-5%; the siliceous mineral content is high, at 60%-70%; the physical properties are good, with a horizontal permeability of 71,500 nD, a vertical permeability of 1,990 nD, and a total pore volume of 0.03 cm³. 3 / g, with a total specific surface area of ​​16.5m². 2 / g, with good brittleness and high compressibility, and a compressibility index of 4.378~5.242.

[0248] The shale in the six high-quality bedding sections is dominated by a graded medium-thick silt-mud layer combination; the residual organic carbon (TOC) is relatively high, at 2%-3%; the siliceous mineral content is relatively high, reaching 40%; the physical properties are good, with a horizontal permeability of 53,300 nD, a vertical permeability of 2,540 nD, and a total pore volume of 0.045 cm³. 3 / g, with a total specific surface area of ​​20.1m². 2 / g, with good brittleness and good compressibility, and a compressibility index of 0.9~1.04.

[0249] Example 3

[0250] A computer device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the reservoir compressibility evaluation method considering shale lamination development characteristics as described in Embodiment 1 or 2.

[0251] Example 4

[0252] A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of a reservoir compressibility evaluation method considering shale lamination development characteristics as described in Embodiment 1 or 2.

[0253] Example 5

[0254] A reservoir compressibility assessment system considering shale lamination development characteristics includes:

[0255] The module for studying the influence of shale lamination development characteristics on mechanical properties is configured as follows: based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes are designed for shale lamination development characteristics to analyze the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamination combinations.

[0256] The module for studying the influence of shale lamination on tensile properties is configured as follows: by conducting Brazilian splitting tests on shale with different lamination groups, the module studies the differences in crack propagation modes and fracture ultimate loads, and then studies the complexity of crack propagation by reflecting the fluctuation of the stress-strain curve after the peak value. The module establishes a graph showing the correlation between relevant parameters of shale lamination structure and fracture toughness, and comprehensively analyzes the influence of shale lamination on tensile properties.

[0257] The module for studying the influence of shale lamination on compressive properties is configured as follows: conducting pseudo-triaxial tests on shale with different lamination groups, observing the differences in artificial crack propagation morphology in shale with different lamination combinations, designing different confining pressure conditions to obtain the ultimate fracture load of shale with different lamination combinations, characterizing shale brittleness by calculating the brittleness index using Young's modulus and Poisson's ratio obtained from rock mechanics tests, analyzing the influence of lamination components on reservoir brittleness, and comprehensively analyzing the influence of shale lamination on compressive properties;

[0258] The longitudinal pressure fracture network through-layer physical simulation experiment module is configured as follows: Considering the stress barrier zone of the laminar fracture network, the longitudinal pressure fracture network through-layer physical simulation experiment is conducted using artificial layered rock samples to simulate the pressure fracture test. The relative magnitude of the triaxial principal stress of the formation is restored by true triaxial loading. Each sub-layer is cast with pure cement and different proportions of quartz sand or soil to achieve different physical and mechanical parameters. Different experiments are designed to study the law of fracture propagation under different interlayer physical property parameter comparisons.

[0259] The longitudinal pressure fracture network penetration finite element numerical simulation module is configured as follows: longitudinal pressure fracture network penetration finite element numerical simulation considering the lamellar stress barrier zone: based on the cohesive finite element method, the mechanism of interaction between hydraulic fractures and bedding planes is studied, and the influence of vertical stress and interface strength on the penetration behavior of hydraulic fractures is revealed.

[0260] The module for studying the influence of lamination development characteristics on the cross-layer behavior of hydraulic fractures is configured as follows: based on the results of physical simulation experiments and finite element numerical simulations, the influence of interlayer stress difference, layer interface properties, and vertical stress caused by lamination on the propagation behavior of fractures at interlayer interfaces is analyzed.

[0261] The module for establishing fracturability evaluation indicators is configured as follows: based on the key factors affecting reservoir fracturability identified in the research, the control effect of key factors on shale reservoir fracturability is comprehensively considered, and evaluation parameters for shale fracturability are established. Then, the parameters are normalized to the same standard using the range standardization method. For indicators that are affected by multiple factors, the multiplication and division of different factors are used to comprehensively reflect their mutual influence.

[0262] The compressibility evaluation module is configured as follows: Distribution location of advantageous lamellar combinations in the target block and reservoir compressibility evaluation: Based on compressibility characteristics, combined with the distribution of high-quality lamellars, reservoir physical properties, mechanical properties and compressibility, establish lamellar iron pillars to clarify the distribution location of advantageous lamellar combinations in the target block and reservoir compressibility.

Claims

1. A method for evaluating reservoir compressibility considering shale lamination development characteristics, characterized in that, Comprise: Step 1: Experimental study on the influence of shale lamina development characteristics on mechanical properties: Based on TOC testing, XRD analysis, Brazilian splitting test, and triaxial compression test, different experimental schemes are designed for shale lamina development characteristics, and the tensile / compressive strength, elastic modulus, Poisson's ratio, and brittleness index of different lamina combinations are analyzed; Step 2: Study on the influence of shale lamina on tensile properties: By conducting Brazilian splitting tests on different lamina group shales, the differences in crack propagation mode and failure limit load are studied, and the complexity of crack propagation is reflected by the fluctuation of the post-peak stress-strain curve. The correlation chart of shale lamina structure-related parameters and fracture toughness is established, and the influence of shale lamina on tensile properties is comprehensively analyzed; Step 3: Study on the influence of shale lamina on compressive properties: Conducting pseudo-triaxial tests on different lamina group shales, observing the differences in artificial crack propagation morphology of different lamina combinations, and designing different confining pressure conditions to obtain the failure limit load of different lamina combinations. The brittleness index calculated by the Young's modulus and Poisson's ratio obtained from rock mechanics tests is used to characterize the brittleness of shale, and the influence of lamina composition on reservoir brittleness is analyzed. The influence of shale lamina on compressive properties is comprehensively analyzed; Step 4: Physical simulation experiment of longitudinal fracturing fracture network crossing layer considering lamina stress barrier: Using artificial layered rock samples for simulation fracturing test, the relative size of the three principal stresses in the formation is restored by true triaxial loading method. Each layer is casted with pure cement and different proportions of quartz sand or soil, so as to have different physical and mechanical parameters. Different test studies are designed to study the law of crack propagation under different interlayer physical property parameter comparison differences; Step 5: Finite element numerical simulation of longitudinal fracturing fracture network crossing layer considering lamina stress barrier: Based on the cohesive force finite element method, the cross action mechanism of hydraulic fracture and bedding plane is studied, and the influence law of vertical stress and interface strength on the behavior of hydraulic fracture crossing layer is revealed; Step 6: Study on the influence law of lamina development characteristics on the behavior of hydraulic fracture crossing layer: Based on the results of physical simulation experiment and finite element numerical simulation, the influence of interlayer geostress difference caused by lamina, layered interface properties, and vertical stress on the expansion behavior of crack on the interlayer interface is analyzed; Step 7: Establishment of fracturing evaluation index for shale reservoir: According to the key factors affecting the fracturing of shale reservoir obtained from the research, the control effect of key factors on the fracturing of shale reservoir is comprehensively considered, and the parameter index for evaluating the fracturing of shale is established. The same standard is corrected by the range standardization method, and the influence of different factors is comprehensively considered by multiplication and division; Step 8: Distribution position of dominant lamina combination and reservoir fracturing in target block: Based on the fracturing characteristics, the distribution of high-quality lamina, reservoir properties, mechanical properties, and fracturing are combined to establish a lamina iron column, and the distribution position of dominant lamina combination and reservoir fracturing in target block is determined.

2. The method of claim 1, wherein, The specific implementation process of Step 2 includes: According to the sample crack propagation morphology, it is divided into central vertical crack, eccentric arc crack and branch type crack, the central vertical crack is pure tensile fracture, the crack propagation mode is single, and the sample fracture limit load of this kind of damage mode is the highest; the sample fracture limit load of eccentric arc crack is lower than that of central vertical crack; the sample fracture limit load of branch type crack is the lowest; According to the shape of the section, it is divided into three types of fracture toughness, including opening type, i.e. type I, staggered type, i.e. type II and tearing type, i.e. type III; the type I fracture toughness empirical formula is selected for calculation: ； wherein K 1c is the mode I fracture toughness, P max is the maximum load at failure in the Brazilian test, kN; B is the sample thickness, cm; and D is the diameter, cm; is the stress intensity factor; A correlation chart of shale lamella structure related parameters and fracture toughness is established.

3. The method of claim 1, wherein, The specific implementation process of step 3 includes: Step 3.1: Perform pseudo-triaxial test on different lamella group shales to observe and determine the differences in artificial crack propagation morphology of different lamella group shales; Step 3.2: Design different confining pressure conditions to obtain different lamella group shale fracture limit loads; Step 3.3: Compare the characteristics of elastic modulus and Poisson's ratio of different lamella groups according to the experimental results; The lamella group ordering from large to small elastic modulus is as follows: the overall presents a gradient thin silt-thick mud lamella group, a gradient thick silt-thin mud lamella group, a gradient medium-thick silt-mud lamella group, an interbedded thick silt-thin mud lamella group, a gradient thick mud lamella group and a massive lamella group shale; The lamella group ordering from small to large Poisson's ratio is as follows: the gradient thin silt-thick mud lamella group, the gradient medium-thick silt-mud lamella group, the gradient thick silt-thin mud lamella group, the interbedded thick silt-thin mud lamella group, the massive lamella group and the gradient thick mud lamella group shale; Step 3.4: Evaluate the effect of laminated components on reservoir brittleness, the brittleness index is calculated by the Young's modulus and Poisson's ratio obtained by rock mechanics test to characterize the brittleness of shale As shown below: ； ； ； where YM represents the static Young's modulus, GPa; YM max represents the maximum static Young's modulus, GPa; YM min represents the minimum static Young's modulus, GPa; YM Brit represents the normalized Young's modulus, 0-1; PR represents the static Poisson's ratio, dimensionless; PR max represents the maximum static Poisson's ratio, dimensionless; PR min represents the minimum static Poisson's ratio, dimensionless; PR Brit represents the normalized static Poisson's ratio, 0-1; A relationship table of mineral composition and brittleness index is established, that is: shale samples with different mineral compositions are selected, the corresponding brittleness indexes are calculated, and then a relationship table of mineral composition and brittleness index is established.

4. The method of claim 1, wherein, The specific implementation process of step 4 is as follows: The simulation fracturing test is performed, including: First step, layered medium simulation; Second step, layered in-situ stress simulation; Third step, interlayer mechanical difference simulation; each small layer is casted with pure cement and different proportions of quartz sand or soil, so as to have different physical and mechanical parameters; Fourth step, interface strength simulation; during the layered casting of the test sample, different interface strengths are simulated by the length of the interval between the casting time of the two layers; The influence of elastic modulus difference, interface cementation strength and interlayer stress difference is studied; The influence of elastic modulus difference includes: Four groups of tests are designed to discuss and study the law of crack propagation under different interlayer physical property parameter comparison differences, and to study the influence of elastic modulus comparison difference on whether the crack can pass through the interlayer interface and enter the barrier layer; The influence of interface cementation strength includes: A number of experiments are designed, and the composition of each layer of the test piece is the same; the difference lies in the interlayer interface properties, the fracturing fluid used in the test, the test loading rate, the pressure on the interface; the influence of the interface properties, the interface stress condition and the test loading rate on the crack morphology is studied for the same test piece.

5. The method of claim 1, wherein, The specific implementation process of step 5 includes: The two influence parameters of in-situ stress and bedding plane strength are dimensionless processed, and the vertical stress difference coefficient is defined as: ； wherein — vertical stress difference coefficient, dimensionless; — minimum horizontal stress, ; — vertical stress, ; The non-dimensional comprehensive bedding strength is defined by the relative size relationship between the bedding plane and the tensile strength of the lower rock and the cohesion of the two tangents, that is, ； wherein — tensile strength of the bedding, ; — tensile strength of the lower rock layer, ; — indicator, ; — cohesion in the first or second tangential direction of the bedding plane; — cohesion in the first or second tangential direction of the lower rock layer; By continuously adjusting the tensile strength, cohesion and vertical stress of the bedding plane, the vertical trans-layer propagation law of hydraulic fractures under different vertical stress difference coefficients and bedding plane strength conditions is studied; after the simulation is completed, according to the different action modes of the hydraulic fractures and the bedding planes, three typical fracture patterns are shown: T-shaped joints, blunt joints with bedding slip and trans-layer joints penetrating the bedding planes; Draw a comprehensive control chart; the lower the bedding plane strength, the smaller the vertical stress difference coefficient, the easier to form a T-shaped joint; the lower the bedding plane strength, the greater the vertical stress difference coefficient, the easier to form a blunt joint; the higher the bedding plane strength, the greater the vertical stress difference coefficient, the easier to form a trans-layer joint.

6. The method for evaluating reservoir compactibility considering shale lamination development characteristics according to claim 1, characterized in that, The specific implementation process of step 6 includes: The gray correlation method is used to evaluate and sort the influencing factors of the fracturing index; the specific analysis includes the following steps: Determine a reference sequence; All sequences are dimensionless; The correlation coefficient C is calculated by the following formula: ； wherein, is the minimum absolute difference between the reference sequence and the subsequence, is the maximum absolute difference between the reference sequence and the subsequence, p is the resolution coefficient, and X is the absolute difference between each value of the reference sequence and the subsequence. The correlation coefficient between the sub-sequence and the reference sequence is obtained by averaging the correlation coefficients obtained by the sub-sequence and the reference sequence; Sort according to the correlation degree of the reference sequence and the sub-sequence.

7. The method of claim 1, wherein, The specific implementation process of step 7 includes: The brittleness index, fracture toughness and compressive strength considering the development characteristics of lamination are used to evaluate the fracturing property of shale; The range standardization method is used for normalization to correct to the same standard: ； ； In the formula, Y is a positive normalized value representing a characteristic index; Y1 is a negative normalized value representing a characteristic index; X is a normal value of a characteristic index; is a maximum value of the characteristic index X; is a minimum value of the characteristic index X; Through multiplication and division of the three normalized indexes, the fracturing index under confining pressure is established, which combines the static brittleness index, fracture toughness and triaxial compressive strength: ； In the formula, F is the fracturing index, dimensionless; B is the normalized positive static brittleness index, dimensionless; K is the normalized negative fracture toughness, dimensionless; σ is the normalized negative triaxial compressive strength, dimensionless.

8. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that, The processor executes the computer program to realize the steps of the reservoir fracturing property evaluation method considering the development characteristics of shale lamination according to any one of claims 1-7.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the reservoir fracturing property evaluation method considering the development characteristics of shale lamination according to any one of claims 1-7.

10. A system for evaluating reservoir compressibility considering shale lamination development characteristics, characterized by, It includes: The shale lamination development characteristic influence on mechanical property research module is configured to: based on TOC test, XRD analysis, Brazilian splitting test and triaxial compression test, different experimental schemes are designed for shale lamination development characteristics, and the tensile / compressive strength, elastic modulus, Poisson's ratio and brittleness index of different lamination combinations are analyzed; The shale lamination influence on tensile property research module is configured to: through the Brazilian splitting test on different lamination group shale, the difference of corresponding crack propagation mode and fracture limit load is studied, and then the crack propagation complexity is reflected by the fluctuation of the post-peak stress-strain curve, the correlation chart of shale lamination structure related parameters and fracture toughness is established, and the influence of shale lamination on tensile property is comprehensively analyzed; The shale lamina effect on compressive property research module is configured to: carry out pseudo-triaxial test on shale with different lamina combinations, observe the difference in artificial crack propagation morphology of shale with different lamina combinations, obtain the breaking limit load of shale with different lamina combinations under different confining pressures, obtain the brittleness index calculated by Young's modulus and Poisson's ratio obtained through rock mechanics test to represent the brittleness of shale, analyze the effect of lamina combination on reservoir brittleness, and comprehensively analyze the effect of shale lamina on compressive property; The longitudinal fracturing fracture network crossing layer physical simulation experiment module is configured to: longitudinal fracturing fracture network crossing layer physical simulation experiment considering lamina stress barrier: artificial layered rock sample is used for simulation fracturing test, true triaxial loading mode is used to restore the relative size of three principal stresses of the formation, pure cement and different proportions of quartz sand or soil are used for casting in each layer to make the physical and mechanical parameters different, and the fracture propagation law under different interlayer physical property parameter comparison differences is designed for test research; The longitudinal fracturing fracture network crossing layer finite element numerical simulation module is configured to: longitudinal fracturing fracture network crossing layer finite element numerical simulation considering lamina stress barrier: based on the finite element method of cohesion force, the cross action mechanism of hydraulic fracture and bedding plane is researched, and the influence law of vertical stress and interface strength on the behavior of hydraulic fracture crossing layer is revealed; The lamina development feature effect on hydraulic fracture crossing layer behavior influence law research module is configured to: based on the results of physical simulation experiment and finite element numerical simulation, the influence of interlayer stress difference caused by lamina, layered interface property, and vertical stress on the expansion behavior of fracture on the interlayer interface is analyzed; The fracturability evaluation index establishment module is configured to: according to the key factors affecting reservoir fracturability obtained through research, the control effect of key factors on shale reservoir fracturability is comprehensively considered, the parameter index for evaluating shale fracturability is established, and the same standard is corrected through range standardization method, for the index affected by multiple factors, the multiplication and division of different factors are used to comprehensively consider the mutual influence; The fracturability evaluation module is configured to: target block advantage lamina combination distribution position and reservoir fracturability evaluation: based on fracturability characteristics, combined with high-quality lamina distribution, reservoir physical property, mechanical property and fracturability, lamina iron column is established, and the target block advantage lamina combination distribution position and reservoir fracturability are determined.

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