A method, apparatus, equipment, and storage medium for assessing the compressibility of shale reservoirs.

Abstract

This invention discloses a method, apparatus, equipment, and storage medium for assessing the compressibility of shale reservoirs. The method includes: obtaining shale core samples from a target formation within a study reservoir area; determining the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core samples; determining a compressibility index based on the rock hardness, Young's modulus, fracture toughness, and brittleness index; and assessing the reservoir compressibility of the target formation based on the compressibility index. The technical solution of this invention, by determining the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core samples, and by determining the compressibility index based on these parameters, enables a continuous, quantitative, and efficient compressibility assessment method for shale reservoirs across the entire well section, improving the accuracy and practicality of shale reservoir compressibility assessment.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, and in particular to a method, apparatus, equipment and storage medium for assessing the compressibility of shale reservoirs. Background Technology

[0002] With the continuous development of fracturing technology, unconventional oil and gas resources have become increasingly prominent in global energy supply. Compressibility assessment is a key step in shale oil and gas fracturing design, used to evaluate the feasibility of reservoir fracturing to form a complex fracture network.

[0003] Currently, there is no unified standard for compressibility evaluation. Existing assessment methods mainly include geophysical interpretation and laboratory experiments, aiming to directly or indirectly obtain rock mechanical properties. However, due to the unstable physicochemical properties of bedding shale, it is difficult to obtain high-quality cores that meet the requirements of conventional mechanical experiments, making it difficult to conduct uniaxial / triaxial compression, tension, and fracture toughness tests. Especially for thin-bedding shale, the limitation of sample size makes conventional experiments impossible. In addition, these experiments are mostly destructive tests, and the results are not repeatable and have high randomness, further limiting their engineering applicability.

[0004] Existing methods also include compressibility prediction models that rely on well logging data, such as estimating mechanical parameters by combining shear wave logging data with rock physics models. However, these methods heavily depend on high-quality logging data and are prone to significant errors in well sections where shear wave data is missing or of poor quality. Existing micromechanical testing methods in shale face challenges such as cumbersome procedures, high economic costs, and limited testing range. They struggle to systematically cover the mechanical responses of the shale matrix and bedding separately, and cannot achieve continuous, centimeter-scale mechanical data acquisition across the entire well section. Furthermore, current research has not yet established a multi-scale equivalent model that effectively combines micromechanical parameters with macroscopic geological features, making it difficult to reliably extrapolate micromechanical data to the engineering scale, thus limiting the accuracy and practicality of shale reservoir compressibility assessment.

[0005] Therefore, there is an urgent need to establish a method for assessing the compressibility of shale reservoirs to conduct continuous, centimeter-scale compressibility assessments of shale reservoirs throughout the entire well section. Summary of the Invention

[0006] This invention provides a method, apparatus, equipment, and storage medium for assessing the compressibility of shale reservoirs, thereby improving the accuracy and practicality of shale reservoir compressibility assessment.

[0007] In a first aspect, embodiments of the present invention provide a method for assessing the compressibility of shale reservoirs, the method comprising: Obtain shale cores of the target strata in the reservoir area under study; Determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core. The compressibility index is determined based on the rock hardness, Young's modulus, fracture toughness, and brittleness index. Based on the compressibility index, reservoir compressibility is assessed for the target strata.

[0008] Secondly, embodiments of the present invention also provide a shale reservoir compressibility assessment device, the device comprising: The core acquisition module is used to acquire shale cores from the target strata in the reservoir area under study. The data determination module is used to determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core. The compressibility index determination module is used to determine the compressibility index based on the rock hardness, rock Young's modulus, rock fracture toughness, and rock brittleness index. The compressibility assessment module is used to assess the reservoir compressibility of the target stratum based on the compressibility index.

[0009] Thirdly, embodiments of the present invention also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the shale reservoir compressibility assessment method as described in any of the embodiments of the present invention.

[0010] Fourthly, embodiments of the present invention also provide a storage medium for storing computer-executable instructions, which, when executed by a computer processor, are used to perform the shale reservoir compressibility assessment method as described in any of the embodiments of the present invention.

[0011] The technical solution of this invention determines the rock hardness, Young's modulus, fracture toughness, and brittleness index of shale cores. Based on these parameters, a compressibility index is determined, and reservoir compressibility is assessed for the target formation. This enables a continuous, quantitative, and efficient compressibility assessment method for shale throughout the entire well section, improving the accuracy and practicality of shale reservoir compressibility assessment.

[0012] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart of a shale reservoir compressibility assessment method provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of core preparation for an indentation and scratch test provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the shale matrix surface and the shale laminar surface in a shale scratch mechanical test provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the load-displacement curves of indentation experiments on laminated core and matrix core provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the compressive strength-displacement curves of a scratch test on a laminated rock core and a matrix rock core provided in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the mineral composition results of an X-ray diffraction test of a laminated rock core and a matrix rock core provided in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the structure of a shale reservoir compressibility assessment device provided in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the electronic device used to implement the shale reservoir compressibility assessment method according to embodiments of the present invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0016] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0017] Example 1 Figure 1 This document provides a flowchart of a shale reservoir compressibility assessment method according to Embodiment 1 of the present invention. This embodiment is applicable to shale reservoir compressibility assessment. The method can be executed by a shale reservoir compressibility assessment device, which can be implemented in hardware and / or software. This device can be configured in any electronic device with network communication and computing capabilities. Figure 1 As shown, the method includes: S110. Obtain shale cores of the target strata in the study reservoir area.

[0018] In this embodiment, the reservoir area under study is the reservoir area for compressibility assessment, and the target layer is the layer with shale oil and gas accumulation. It should be noted that the target layer must contain exploitable shale gas and oil resources, and it must be the layer in which horizontal well drilling and multi-stage fracturing are actually planned in the field. It is the core of the entire compressibility assessment spatial range, and all core drilling, experimental testing, and parameter analysis in actual application are carried out around this target layer.

[0019] In this embodiment, regional geological data, adjacent well drilling data, and well logging data can be combined to determine the depth range, lithological characteristics, and bedding patterns of the reservoir in the study area, thus delineating the target strata. Detailed well logging interpretation is performed using the target wells, employing gamma, density, sonic, and resistivity logging curves to identify the lithological interfaces and reservoir thickness of the shale reservoir. The well depth and inclination of the target strata are then precisely determined. Core drilling techniques are then employed, with directional and vertical core drilling schemes designed for the target strata to extract shale cores.

[0020] Furthermore, the surface of the core column was precisely cut to a depth of approximately 5 mm along the direction perpendicular to the bedding plane to prepare a smooth test surface that meets the requirements of macroscopic centimeter-level pressure / scratch tests.

[0021] See Figure 2The diagram shows a core preparation for an indentation / scratch test. This core can be used for shale indentation / scratch tests. The indentation / scratch test can be performed by using a high-precision core cutter to make a precision cut of about 5 mm along the direction perpendicular to the bedding plane, so as to prepare a flat cut surface to meet the requirements of macroscopic centimeter-level indentation / scratch tests. The indentation / scratch test is performed along the scratch direction shown in the figure.

[0022] S120. Determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core.

[0023] In this embodiment, after obtaining the shale core, the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core can be determined based on centimeter-level indentation-scratch combined experiments. Through centimeter-level indentation and scratch experiments, continuous and efficient measurement of key mechanical parameters such as hardness, Young's modulus, and fracture toughness of the entire shale well section can be achieved, overcoming the limitations of localized sampling in microscopic testing, which cannot reflect the heterogeneous characteristics at the engineering scale.

[0024] Specifically, the surface of the core column was precisely cut to a depth of about 5 mm along the direction perpendicular to the bedding to prepare a smooth test surface that meets the requirements of macroscopic centimeter-level indentation-scratch experiments, representing the shale core.

[0025] In this embodiment, rock hardness refers to the ability of a shale core to resist plastic deformation caused by the indentation of a diamond indenter, characterizing the degree of hardness of shale against external mechanical loads; rock Young's modulus refers to the ratio of stress applied by the indenter to the strain generated during the elastic deformation stage of shale, characterizing the elastic deformation capacity of shale and reflecting the characteristic of the rock to recover its original shape after being loaded; rock fracture toughness characterizes the ability of shale to resist crack initiation, propagation, and unstable fracture, reflecting the ease with which the rock undergoes brittle fracture; rock brittleness index refers to the degree of brittleness of shale.

[0026] In this embodiment, by obtaining the rock hardness, Young's modulus, fracture toughness, and brittleness index of shale cores, data are provided for the subsequent assessment of the compressibility of shale reservoirs in the target strata.

[0027] Optionally, determining the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core includes: The shale cores were classified to obtain laminated cores and matrix cores; Volume fraction analysis was performed on the shale core to determine the volume fraction of the laminae and the volume fraction of the matrix. Based on the volume ratio of the laminae and the volume ratio of the matrix, the rock hardness, Young's modulus, fracture toughness, and fracture toughness of the shale core are determined.

[0028] In this embodiment, the lamellar core is shale with clear horizontal lamellars and rhythmic bedding, and the matrix core is shale with no obvious bedding or very poor bedding. The lamellar volume ratio is the volume ratio coefficient of the lamellar core in the shale core, and the matrix volume ratio is the volume ratio coefficient of the matrix core in the shale core.

[0029] See Figure 3 The diagram shows the surface of the shale matrix and the surface of the shale lamellar layer in a shale scratch mechanical test. The shale matrix surface has no obvious bedding, while the shale lamellar surface has clear horizontal bedding.

[0030] In practical applications, shale cores are classified into lamellar cores and matrix cores based on their texture and matrix samples. These cores are then ground and polished separately to ensure that the surface roughness meets the requirements for centimeter-scale mechanical testing.

[0031] Furthermore, through microscopic observation and image analysis of the cut samples, the thickness distribution of the laminae and matrix was statistically analyzed. A multi-scale thickness model was established using fractal theory to calculate the volume ratio of the laminae and matrix. The calculation method is as follows: ; ; ; Among them, the scale of the target fracturing section L frac The total thickness of the target fracturing section is H frac The total layer thickness is H lam-total , This represents the percentage of the laminar volume. This represents the percentage of matrix volume.

[0032] Furthermore, based on the volume ratio of laminae and matrix in the shale core, and considering the difference in mechanical contribution between laminae and matrix, a parameter sensitivity coefficient is introduced to construct an equivalent parameter calculation model with dual weights of volume ratio and mechanical contribution. This achieves a scale upgrade of micro-parameters, and the rock hardness, Young's modulus, fracture toughness, and fracture toughness of the shale core are calculated respectively.

[0033] Optionally, the rock hardness of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Indentation tests were performed on both the lamellar core and the matrix core to determine the lamellar hardness and the matrix hardness. The rock hardness is determined based on the lamellar volume ratio, matrix volume ratio, lamellar hardness, and matrix hardness.

[0034] In this embodiment, the laminar hardness is the hardness of the laminar core, the matrix hardness is the hardness of the matrix core, and the rock hardness is the hardness of the shale core.

[0035] In this embodiment, a centimeter-level indentation test device was used to perform indentation tests on the lamellar core and the matrix core respectively to obtain the corresponding parameters of lamellar hardness and matrix hardness.

[0036] Specifically, at least two parallel test points were set for each laminated core and matrix core. The test adopted a linear loading-holding-linear unloading mode, and the complete load-displacement curve was recorded synchronously to obtain the hardness parameters.

[0037] See Figure 4 The figure shows a schematic diagram of the load-displacement curves of indentation experiments on laminated core and matrix core, with the load corresponding to the compressive strength.

[0038] Furthermore, based on the recorded load-displacement curves, it is necessary to first derive the contact depth between the indenter and each core sample, and then calculate the contact area and hardness value. The corresponding hardness calculation formula is as follows: ; ; ; in, This represents the contact depth between the indenter and the sample. For maximum indentation depth, This is the geometric correction factor for the indenter head. To determine the unloading stiffness, the unloading stiffness is obtained by linearly fitting the load-displacement curve before the unloading segment. H represents the projected contact area between the indenter and the core, and H represents the hardness of the core.

[0039] Furthermore, the hardness of the laminated core and the matrix core can be calculated using the above formulas, thus determining the laminated hardness and matrix hardness.

[0040] It should be noted that the indenter depth was set to 2 mm in the experiment, and a linear loading-holding-unloading mode was adopted. The pressing speed was controlled at 0.2 mm / s. At least 15 effective tests were completed for each group of samples, and the arithmetic mean of the results was taken as the layer hardness and matrix hardness.

[0041] Furthermore, based on the volume ratio of laminae, the volume ratio of matrix, the hardness of laminae, and the hardness of matrix, the rock hardness is determined using the following formula: ; in, The rock hardness of the shale assemblage is expressed in MPa. The hardness of the inlay is MPa. The matrix hardness is measured in MPa. This represents the percentage of the laminar volume. This represents the percentage of matrix volume.

[0042] In this embodiment, the rock hardness is calculated based on a dual weight of volume ratio and hardness, thereby achieving a scale upgrade of micro-parameters and improving the accuracy of rock hardness calculation.

[0043] Optionally, the Young's modulus of the shale core is determined based on the volume ratio of the laminae and the volume ratio of the matrix, including: Indentation tests were performed on the bedding core and the matrix core to determine the Young's modulus of the bedding and the matrix, respectively. The Young's modulus of the rock is determined based on the volume ratio of the laminae, the volume ratio of the matrix, the Young's modulus of the laminae, and the Young's modulus of the matrix.

[0044] In this embodiment, the Young's modulus of the lamellar core is the Young's modulus of the lamellar core, the Young's modulus of the matrix core is the Young's modulus of the matrix core, and the Young's modulus of the rock core is the Young's modulus of the shale core.

[0045] In this embodiment, a centimeter-level indentation testing device can be used to perform indentation tests on the bedding core and the matrix core respectively to obtain the corresponding parameters of the bedding Young's modulus and the matrix Young's modulus.

[0046] Specifically, the formulas for calculating the Young's modulus of the laminae and the Young's modulus of the matrix in the corresponding centimeter indentation test are as follows: ; ; in, Poisson's ratio of shale core samples (obtained through ultrasonic P- and S-wave tests; Poisson's ratio of laminated sample S1 is:) v li The Poisson's ratio of matrix sample S2 is v mi ; v i , E i These are Poisson's ratio and Young's modulus of the diamond indenter, respectively.

[0047] Furthermore, the Young's modulus of the bedding core and the matrix core can be calculated using the above formulas, thus determining the Young's modulus of the bedding core and the matrix core.

[0048] It should be noted that the indenter depth was set to 2 mm in the experiment, and a linear loading-holding-unloading mode was adopted. The pressing speed was controlled at 0.2 mm / s. At least 15 effective tests were completed for each group of samples, and the arithmetic mean of the results was taken as the Young's modulus of the laminae and the Young's modulus of the matrix.

[0049] Furthermore, based on the volume ratio of the laminae, the volume ratio of the matrix, the Young's modulus of the laminae, and the Young's modulus of the matrix, the Young's modulus of the rock is determined and calculated using the following formula: ; in, The rock hardness of the shale assemblage is expressed in MPa. The hardness of the inlay is MPa. The matrix hardness is measured in MPa. This represents the percentage of the lamellar volume. This represents the percentage of matrix volume.

[0050] In this embodiment, the Young's modulus of rock is calculated based on a dual weight of volume ratio and Young's modulus, thereby achieving a scale upgrade of micro-parameters and improving the accuracy of Young's modulus calculation.

[0051] Optionally, the rock fracture toughness of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Scratch tests were performed on both the lamellar core and the matrix core to determine the fracture toughness of the lamellar core and the matrix core, respectively. The rock fracture toughness is determined based on the laminar volume ratio, matrix volume ratio, laminar fracture toughness, and matrix fracture toughness.

[0052] In this embodiment, the lamellar fracture toughness is the fracture toughness of the lamellar core, the matrix fracture toughness is the fracture toughness of the matrix core, and the rock fracture toughness is the fracture toughness of the shale core.

[0053] In this embodiment, scratch testing can be performed on the same batch of samples using a centimeter-level scratch testing device to obtain parameters of lamellar fracture toughness and matrix fracture toughness.

[0054] See Figure 5 The diagram shows the compressive strength-displacement curves of scratch tests on laminated core and matrix core, with compressive strength versus stress data.

[0055] Specifically, based on the force and displacement data recorded in the centimeter scratch test, the equivalent load and indenter shape function need to be calculated first, and then the fracture toughness is derived by combining the strain energy release rate, taking into account the size effect correction, and calculated using the following formula: ; ; ; ; In this process, the combined effect of tangential and perpendicular forces during the scratching process is considered, and the equivalent load is calculated. , Let k2 be the indenter shape function, and k3 be the force distribution coefficients, where k2 + k3 = 1. The scratch depth is obtained from a subsequent scan. The strain energy release rate, based on the theory of linear elastic fracture mechanics, reflects the energy required per unit area for crack propagation. This represents the corresponding core fracture toughness.

[0056] Furthermore, the fracture toughness of the laminated core and the matrix core can be calculated using the above formulas, thus determining the fracture toughness of the laminated core and the matrix core.

[0057] It should be noted that the scratch length is set to 100 mm, the scratch speed is 0.4 mm / s, and the effective number of scratches for each group of laminated core and matrix core is no less than 10. The arithmetic mean is taken as the final lamellar fracture toughness and matrix fracture toughness.

[0058] Furthermore, based on the volume ratio of laminae and matrix, the fracture toughness of laminae, and the fracture toughness of matrix, the fracture toughness of the rock is determined by the following formula: ; in, For rock fracture toughness, For laminar fracture toughness, For matrix fracture toughness, This represents the percentage of the laminar volume. This represents the percentage of matrix volume.

[0059] In this embodiment, the rock fracture toughness is calculated based on a dual weight of volume ratio and fracture toughness, thereby achieving a scale upgrade of micro-parameters and improving the accuracy of rock fracture toughness.

[0060] Optionally, the rock brittleness index of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Quantitative mineral composition analysis was performed on lamellar cores and matrix cores to determine the lamellar brittleness index and matrix brittleness index. The rock brittleness index is determined based on the lamellar volume ratio, matrix volume ratio, lamellar brittleness index, and matrix brittleness index.

[0061] In this embodiment, the laminar brittleness index is the brittleness index of the laminar core, the matrix brittleness index is the brittleness index of the matrix core, and the rock brittleness index is the brittleness index of the shale core.

[0062] In this embodiment, X-ray diffraction technology can be used to quantitatively analyze the mineral composition of samples from lamellar cores and matrix cores, focusing on extracting the content of brittle minerals, and calculating the lamellar brittleness index and matrix brittleness index accordingly.

[0063] See Figure 6 The diagram shows the mineral composition results of X-ray diffraction tests on laminated core and matrix core. The core contains elements such as Al, S, Si, K, Ca, Fe, Mg and Ti.

[0064] For laminated core samples and matrix core samples, considering their mineral composition and distribution characteristics, a mineral brittleness weighting coefficient is introduced to quantify the contribution of different minerals to brittleness. A brittleness index calculation model specific to laminated and matrix cores is constructed. The shale mineral composition consists of quartz, feldspar, calcite, dolomite, and clay minerals. The laminar brittleness index and matrix brittleness index can be calculated using the following formula: ; ; in, B lam and B mat It is divided into lamellar brittleness index and matrix brittleness index, with the corresponding brittle mineral weighting coefficient being W for quartz. Q Feldspar W F Calcium W C Dolomite W D clay mineral W Cl Mineral composition analysis revealed that the percentage of minerals in the laminated core was quartz Q. Q-lam Feldspar Q F-lam Calcium Q C-lam Dolomite Q D-lam clay mineral Q Cl-lam The percentage of mineral content in the matrix core was quartz Q. Q-mat Feldspar Q F-mat Calcium Q C-mat Dolomite Q D-mat clay mineral Q Cl-mat .

[0065] In this embodiment, the laminar brittleness index and the matrix brittleness index can be calculated using the above formulas.

[0066] Furthermore, based on the volume ratio of laminations, the volume ratio of matrix, the lamination brittleness index, and the matrix brittleness index, the rock brittleness index is determined using the following formula: ; in, The rock brittleness index. The lamininity index is the brittleness index. The matrix brittleness index, This represents the percentage of the laminar volume. This represents the percentage of matrix volume.

[0067] In this embodiment, the rock brittleness index is calculated based on a dual weight of volume ratio and brittleness index, thereby achieving a scale upgrade of micro-parameters and improving the accuracy of the rock brittleness index.

[0068] S130. Determine the compressibility index based on the rock hardness, Young's modulus, fracture toughness, and brittleness index.

[0069] In this embodiment, the compressibility index is used to reflect the compressibility of the shale reservoir where the shale core is located. By comprehensively utilizing rock hardness, Young's modulus, fracture toughness, and brittleness index, the compressibility of the shale reservoir where the shale core is located is evaluated, ensuring the accuracy of the shale reservoir compressibility assessment.

[0070] Specifically, in this embodiment, the rock hardness, Young's modulus, fracture toughness, and brittleness index can be normalized first through dynamic range transformation. Then, based on the analytic hierarchy process and adjacent well fracturing engineering data, the evaluation weight of each parameter on compressibility is determined. Based on the evaluation weight of each parameter, a comprehensive compressibility evaluation model for layered shale reservoirs is constructed. The compressibility index of the target layer in the reservoir area where the shale core is located is determined through the summative compressibility evaluation model.

[0071] Optionally, the compressibility index is determined based on the rock hardness, Young's modulus, fracture toughness, and brittleness index, including: Determine the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight; the sum of the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight is 1; The rock hardness, Young's modulus, fracture toughness, and brittleness index were normalized to obtain standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index. The compressibility index is obtained by weighting and summing the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, preset brittleness index weight, standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index.

[0072] In this embodiment, the preset hardness weight is a pre-set rock hardness weight coefficient, the preset Young's modulus weight is a pre-set rock Young's modulus weight coefficient, the preset fracture toughness weight is a pre-set rock fracture toughness weight coefficient, and the preset brittleness index weight is a pre-set rock brittleness index weight coefficient. The sum of the preset hardness weight, the preset Young's modulus weight, the preset fracture toughness weight, and the preset brittleness index weight is 1.

[0073] In practical applications, the preset weights for hardness, Young's modulus, fracture toughness, and brittleness index can be flexibly set. Alternatively, the influence of each parameter on the compressibility index can be determined based on the analytic hierarchy process combined with actual adjacent well fracturing engineering data, and the weight coefficients of each parameter can be determined.

[0074] In this embodiment, the standard hardness is the normalized rock hardness, the standard Young's modulus is the normalized rock hardness, the standard fracture toughness is the normalized rock fracture toughness, and the standard brittleness index is the normalized rock brittleness index.

[0075] It should be noted that normalizing the rock hardness, Young's modulus, fracture toughness, and brittleness index eliminates the influence of dimensional inconsistencies and ensures the accuracy of the compressibility index.

[0076] Specifically, for the compressibility index based on rock hardness, maximum value normalization is used, and the normalized standard hardness can be calculated using the following formula: ; in, Standard hardness, For rock hardness, This represents the maximum hardness of the rock. This represents the minimum rock hardness.

[0077] For compressibility indices based on Young's modulus of rock, maximum normalization is used. The normalized standard Young's modulus can be calculated using the following formula: ; in, Standard hardness, For rock hardness, This represents the maximum hardness of the rock. This represents the minimum rock hardness.

[0078] The fracture toughness of rocks, obtained after processing based on the size effect law, represents the material's resistance to crack propagation. Therefore, the smaller the value, the easier it is for cracks to propagate. A minimum value is used to normalize the rock fracture toughness, and the normalized standard fracture toughness can be calculated using the following formula: ; in, Standard hardness, For rock hardness, This represents the maximum hardness of the rock. This represents the minimum rock hardness.

[0079] For the mineralogical brittleness index, the maximum value is normalized, and the normalized standard brittleness index can be calculated by the following formula: ; in, Standard hardness, For rock hardness, This represents the maximum hardness of the rock. This represents the minimum rock hardness.

[0080] Among them, the normalized standard hardness, standard Young's modulus, and standard brittleness index are positive indicators, while the normalized standard fracture toughness is a negative indicator. Positive indicators are those with higher values, and negative indicators are those with lower values, and vice versa.

[0081] Furthermore, the compressibility index is obtained by weighting and summing the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, preset brittleness index weight, standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index. The compressibility index is determined by the following formula: ; ; in, The compressibility index, , , , These are preset weights for hardness, Young's modulus, fracture toughness, and brittleness index, respectively. , , , These are standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index, respectively.

[0082] In this embodiment, the compressibility index of shale core is determined by comprehensively considering four parameters: hardness, Young's modulus, fracture toughness, and brittleness index. This ensures the accuracy of the compressibility index and provides a data basis for subsequent assessment of the compressibility of the target stratum by determining the compressibility index of the shale core.

[0083] S140. Based on the compressibility index, assess the reservoir compressibility of the target stratum.

[0084] In this embodiment, the compressibility of the target stratum in the reservoir area is evaluated by the compressibility index of the shale core of the target stratum, so as to realize the continuous and quantitative classification of the compressibility of shale reservoirs, provide a basis for engineering layer selection and fracturing design, and provide reliable data support for the selection of fracturing sweet spots and the optimization of stimulation schemes in shale reservoirs.

[0085] Specific Implementation Cases This invention targets a semi-cylindrical shale core after long-term diversion, with the planar side being the fracture wall and the curved side being the original surrounding rock contact surface. The method provided by this invention is used to assess the compressibility of the target stratum.

[0086] In practical applications, fresh shale cores with a diameter ≥50mm are first drilled from the target strata in the reservoir study area to ensure that the cores do not undergo hydration swelling or mechanical property deterioration during transportation and storage. A high-precision core cutter is used to precisely cut the surface of the core column to a depth of approximately 5mm along the direction perpendicular to the bedding plane, preparing a smooth test surface that meets the requirements of macroscopic centimeter-level indentation-scratch experiments. Subsequently, two types of samples, "bedding-enriched zones" and "matrix-enriched zones," are separated using directional cutting technology and labeled as laminated cores and matrix cores, respectively.

[0087] Furthermore, the test surfaces of the laminated core and matrix core were subjected to mechanical polishing and argon ion polishing in sequence. In the mechanical polishing stage, 400#, 800#, 1200#, and 2000# silicon carbide sandpaper were used for grinding in stages, with each grinding time controlled at 15-20 minutes to ensure that the surface roughness was initially reduced to Ra≤2μm. In the argon ion polishing stage, an argon ion polisher was used, with the ion beam energy set to 600eV-800eV and the polishing time to 30-45 minutes, so that the surface roughness of the laminated core and matrix core met Ra≤0.5μm, eliminating the interference of surface micro-defects on subsequent mechanical tests.

[0088] Furthermore, the polished laminated core and matrix core were immersed in acetone solution for 15 minutes to remove sandpaper debris remaining from mechanical polishing. They were then transferred to deionized water and ultrasonically cleaned for 20-30 minutes to thoroughly remove oil and minute impurities from the sample surface. After cleaning, the samples were placed in a vacuum drying oven to dry for 2-3 hours until the sample mass became constant.

[0089] Furthermore, based on the centimeter indentation-scratch test, at least two parallel test points were set for each lamellar core and matrix core. The test adopted a linear loading-holding-linear unloading mode, and the complete load-displacement curve was recorded simultaneously to obtain lamellar hardness, matrix hardness, lamellar Young's modulus, matrix Young's modulus, lamellar fracture toughness, matrix fracture toughness, lamellar brittleness index, and matrix brittleness index.

[0090] Furthermore, determining the volume ratio of laminae and matrix in shale reservoirs can be achieved by combining multi-scale observations with fractal theory to accurately calculate the volume ratio of laminae and matrix in shale cores, thus reflecting the volume ratio of laminae and matrix within the target fracturing section.

[0091] Furthermore, considering the difference in mechanical contribution between the laminae and the matrix, a parameter sensitivity coefficient is introduced to construct an equivalent parameter calculation model with dual weights of volume proportion and mechanical contribution. This achieves a scale upgrade of micro-parameters. The mechanical data obtained from nanoindentation and nanoscraping, such as the hardness parameters, Young's modulus parameters, fracture toughness parameters, and brittleness index of the laminae and matrix, are combined to determine the rock hardness, rock Young's modulus, rock fracture toughness, and rock brittleness index using the above formulas.

[0092] Furthermore, using the four parameters mentioned above—rock hardness, rock Young's modulus, rock fracture toughness, and rock brittleness index—the normalization process is first completed through dynamic range transformation. Then, based on the analytic hierarchy process (AHP) combined with fracturing engineering data from adjacent wells, the evaluation weight of each parameter on compressibility is determined. Based on the preset weights of each parameter, a comprehensive compressibility evaluation model for layered shale reservoirs is constructed, and the compressibility index of shale cores is calculated using the above formula.

[0093] Furthermore, the compressibility index of shale cores at the target strata is used to assess the compressibility of the target strata in the reservoir study area, enabling continuous and quantitative classification of shale reservoir compressibility. This provides a basis for engineering stratum selection and fracturing design, and offers reliable data support for the selection of fracturing sweet spots and optimization of stimulation schemes in shale reservoirs.

[0094] This invention causes minimal damage to shale cores during testing, preserving the integrity of the core structure and supporting subsequent experimental analyses, thus improving core sample utilization and the multidimensional value of experimental data. Furthermore, the obtained centimeter-scale mechanical parameters can be directly used to establish engineering-scale compressibility evaluation standards without requiring complex multi-scale upgrade models, significantly simplifying the analysis process and enhancing the field applicability of the evaluation results. Simultaneously, this invention combines macroscopic mechanical parameters with mineral composition analysis, constructing a compressibility index through a combined weighting algorithm, achieving a deep integration of mechanical behavior and mineral composition, resulting in more comprehensive and reliable compressibility evaluation results.

[0095] The technical solution of this invention determines the rock hardness, Young's modulus, fracture toughness, and brittleness index of shale cores through a combined centimeter-level indentation-scratch experiment. Based on the rock hardness, Young's modulus, fracture toughness, and brittleness index, a compressibility index is determined, and reservoir compressibility is assessed for the target formation. This achieves a continuous, quantitative, and efficient compressibility assessment method for shale throughout the entire well section, improving the accuracy and practicality of shale reservoir compressibility assessment.

[0096] Example 2 Figure 7This is a schematic diagram of a shale reservoir compressibility assessment device provided in Embodiment 2 of the present invention. This embodiment is applicable to shale reservoir compressibility assessment. The shale reservoir compressibility assessment device can be implemented in hardware and / or software, and can be configured in any electronic device with network communication and computing capabilities. Figure 7 As shown, the device includes: Core acquisition module 310 is used to acquire shale cores of the target strata in the reservoir area under study; The data determination module 320 is used to determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core. The compressibility index determination module 330 is used to determine the compressibility index based on the rock hardness, rock Young's modulus, rock fracture toughness and rock brittleness index. The compressibility assessment module 340 is used to assess the reservoir compressibility of the target stratum based on the compressibility index.

[0097] Optionally, determining the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core includes: The shale cores were classified to obtain laminated cores and matrix cores; Volume fraction analysis was performed on the shale core to determine the volume fraction of the laminae and the volume fraction of the matrix. Based on the volume ratio of the laminae and the volume ratio of the matrix, the rock hardness, Young's modulus, fracture toughness, and fracture toughness of the shale core are determined.

[0098] Optionally, the rock hardness of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Indentation tests were performed on both the lamellar core and the matrix core to determine the lamellar hardness and the matrix hardness. The rock hardness is determined based on the lamellar volume ratio, matrix volume ratio, lamellar hardness, and matrix hardness.

[0099] Optionally, the Young's modulus of the shale core is determined based on the volume ratio of the laminae and the volume ratio of the matrix, including: Indentation tests were performed on the bedding core and the matrix core to determine the Young's modulus of the bedding and the matrix, respectively. The Young's modulus of the rock is determined based on the volume ratio of the laminae, the volume ratio of the matrix, the Young's modulus of the laminae, and the Young's modulus of the matrix.

[0100] Optionally, the rock fracture toughness of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Scratch tests were performed on both the lamellar core and the matrix core to determine the fracture toughness of the lamellar core and the matrix core, respectively. The rock fracture toughness is determined based on the laminar volume ratio, matrix volume ratio, laminar fracture toughness, and matrix fracture toughness.

[0101] Optionally, the rock brittleness index of the shale core is determined based on the lamellar volume ratio and the matrix volume ratio, including: Quantitative mineral composition analysis was performed on lamellar cores and matrix cores to determine the lamellar brittleness index and matrix brittleness index. The rock brittleness index is determined based on the lamellar volume ratio, matrix volume ratio, lamellar brittleness index, and matrix brittleness index.

[0102] Optionally, the compressibility index is determined based on the rock hardness, Young's modulus, fracture toughness, and brittleness index, including: Determine the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight; the sum of the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight is 1; The rock hardness, Young's modulus, fracture toughness, and brittleness index were normalized to obtain standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index. The compressibility index is obtained by weighting and summing the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, preset brittleness index weight, standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index.

[0103] The technical solution of this invention determines the rock hardness, Young's modulus, fracture toughness, and brittleness index of shale cores. Based on these parameters, a compressibility index is determined, and reservoir compressibility is assessed for the target formation. This enables a continuous, quantitative, and efficient compressibility assessment method for shale throughout the entire well section, improving the accuracy and practicality of shale reservoir compressibility assessment.

[0104] The shale reservoir compressibility assessment device provided in this embodiment of the invention can execute the shale reservoir compressibility assessment method provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method.

[0105] Example 3 Figure 8A schematic diagram of an electronic device 10, which can be used to implement embodiments of the present invention, is shown. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the invention described and / or claimed herein.

[0106] like Figure 8 As shown, the electronic device 10 includes at least one processor 11 and a memory, such as a read-only memory (ROM) 12 or a random access memory (RAM) 13, communicatively connected to the at least one processor 11. The memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes based on the computer program stored in the ROM 12 or loaded from storage unit 18 into the RAM 13. The RAM 13 can also store various programs and data required for the operation of the electronic device 10. The processor 11, ROM 12, and RAM 13 are interconnected via a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0107] Multiple components in electronic device 10 are connected to I / O interface 15, including: input unit 16, such as keyboard, mouse, etc.; output unit 17, such as various types of displays, speakers, etc.; storage unit 18, such as disk, optical disk, etc.; and communication unit 19, such as network card, modem, wireless transceiver, etc. Communication unit 19 allows electronic device 10 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0108] Processor 11 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. Processor 11 performs the various methods and processes described above, such as shale reservoir compressibility assessment methods.

[0109] In some embodiments, the shale reservoir compressibility assessment method may be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program may be loaded and / or installed on electronic device 10 via ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the shale reservoir compressibility assessment method described above may be performed. Alternatively, in other embodiments, processor 11 may be configured to perform the shale reservoir compressibility assessment method by any other suitable means (e.g., by means of firmware).

[0110] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication unit 19, or installed from storage unit 18, or installed from ROM 12. When the computer program is executed by processor 11, it performs the functions defined in the methods of the embodiments of the present invention.

[0111] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip (SoCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0112] Computer programs used to implement the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0113] In the context of this invention, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0114] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0115] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or middleware components (e.g., application servers), or frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0116] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0117] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0118] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for assessing the compressibility of shale reservoirs, characterized in that, include: Obtain shale cores of the target strata in the reservoir area under study; Determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core. The compressibility index is determined based on the rock hardness, Young's modulus, fracture toughness, and brittleness index. Based on the compressibility index, reservoir compressibility is assessed for the target strata.

2. The method according to claim 1, characterized in that, Determining the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core includes: The shale cores were classified to obtain laminated cores and matrix cores; Volume fraction analysis was performed on the shale core to determine the volume fraction of the laminae and the volume fraction of the matrix. Based on the volume ratio of the laminae and the volume ratio of the matrix, the rock hardness, Young's modulus, fracture toughness, and fracture toughness of the shale core are determined.

3. The method according to claim 2, characterized in that, The rock hardness of the shale core is determined based on the lamellar volume ratio and matrix volume ratio, including: Indentation tests were performed on both the lamellar core and the matrix core to determine the lamellar hardness and the matrix hardness. The rock hardness is determined based on the lamellar volume ratio, matrix volume ratio, lamellar hardness, and matrix hardness.

4. The method according to claim 2, characterized in that, The Young's modulus of the shale core is determined based on the volume ratio of the laminae and the volume ratio of the matrix, including: Indentation tests were performed on the bedding core and the matrix core to determine the Young's modulus of the bedding and the matrix, respectively. The Young's modulus of the rock is determined based on the volume ratio of the laminae, the volume ratio of the matrix, the Young's modulus of the laminae, and the Young's modulus of the matrix.

5. The method according to claim 2, characterized in that, The rock fracture toughness of the shale core is determined based on the lamellar volume ratio and matrix volume ratio, including: Scratch tests were performed on both the lamellar core and the matrix core to determine the fracture toughness of the lamellar core and the matrix core, respectively. The rock fracture toughness is determined based on the laminar volume ratio, matrix volume ratio, laminar fracture toughness, and matrix fracture toughness.

6. The method according to claim 2, characterized in that, The rock brittleness index of the shale core is determined based on the lamellar volume ratio and matrix volume ratio, including: Quantitative mineral composition analysis was performed on lamellar cores and matrix cores to determine the lamellar brittleness index and matrix brittleness index. The rock brittleness index is determined based on the lamellar volume ratio, matrix volume ratio, lamellar brittleness index, and matrix brittleness index.

7. The method according to claim 1, characterized in that, The compressibility index is determined based on the rock hardness, Young's modulus, fracture toughness, and brittleness index, including: Determine the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight; the sum of the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, and preset brittleness index weight is 1; The rock hardness, Young's modulus, fracture toughness, and brittleness index were normalized to obtain standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index. The compressibility index is obtained by weighting and summing the preset hardness weight, preset Young's modulus weight, preset fracture toughness weight, preset brittleness index weight, standard hardness, standard Young's modulus, standard fracture toughness, and standard brittleness index.

8. A device for assessing the compressibility of shale reservoirs, characterized in that, include: The core acquisition module is used to acquire shale cores from the target strata in the reservoir area under study. The data determination module is used to determine the rock hardness, Young's modulus, fracture toughness, and brittleness index of the shale core. The compressibility index determination module is used to determine the compressibility index based on the rock hardness, rock Young's modulus, rock fracture toughness, and rock brittleness index. The compressibility assessment module is used to assess the reservoir compressibility of the target stratum based on the compressibility index.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the shale reservoir compressibility assessment method as described in any one of claims 1-7.

10. A storage medium for storing computer-executable instructions, characterized in that, The computer-executable instructions, when executed by a computer processor, are used to perform the shale reservoir compressibility assessment method as described in any one of claims 1-7.

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