Fine evaluation method, device, storage medium and program product of continuous brittleness index based on scratch test under true triaxial stress

Abstract

The application provides a continuous brittleness index fine evaluation method, device, storage medium and program product based on a scratch test under true triaxial stress. The method comprises the following steps: obtaining a core sample of a target reservoir; performing a continuous scratch test on the core sample to obtain a plurality of mechanical response indexes; performing first calculation processing according to the mechanical response indexes to obtain a rock strength brittleness index; performing second calculation processing according to the mechanical response indexes to obtain a rock deformation brittleness index; performing third calculation processing according to the mechanical response indexes to obtain an energy evolution brittleness index; and determining a comprehensive brittleness index for evaluating the brittleness of shale in the target reservoir according to the rock strength brittleness index, the rock deformation brittleness index and the energy evolution brittleness index, so as to improve the accuracy of shale brittleness evaluation.

Description

Technical Field

[0001] This application relates to the fields of rock mechanics and unconventional oil and gas development technology, and in particular to a method, equipment, storage medium and program product for fine evaluation of continuous brittleness index based on scratch test under true triaxial stress. Background Technology

[0002] As a crucial component of unconventional oil and gas resources, the core challenge in the exploration and development of shale oil and gas lies in assessing the fracturability of the reservoir. The shale brittleness index is a key parameter characterizing reservoir fracturability, directly influencing the complexity of the fracture network during hydraulic fracturing. Highly brittle shale tends to form network fractures, while low-brittle areas are dominated by single fractures, leading to significant differences in fracturing effectiveness. Shale reservoir development faces challenges from extreme environments and strong heterogeneity; therefore, there is an urgent need to develop new technologies to improve the ability to assess reservoir brittleness.

[0003] Existing technologies for evaluating brittleness mainly include the mineral composition method, the elastic parameter method, and the stress-strain method. The mineral composition method evaluates brittleness based on the proportion of brittle minerals such as quartz and carbonates, but neglects mechanical response characteristics. The elastic parameter method inverts dynamic Young's modulus and Poisson's ratio from well logging data, but cannot characterize the mechanical abrupt changes in laminae at the millimeter-centimeter level. The stress-strain method relies on the amount of plastic deformation before rock failure to evaluate brittleness; its physical meaning is clear, but it typically relies on single-point testing and destructive experiments, resulting in high sample preparation costs and inability to be applied in situ.

[0004] Therefore, existing technologies suffer from insufficient accuracy in evaluating the brittleness of shale. Summary of the Invention

[0005] This application provides a method, device, storage medium, and program product for fine evaluation of continuous brittleness index based on scratch test under true triaxial stress, so as to achieve the effect of accurately evaluating the brittleness of shale.

[0006] In a first aspect, embodiments of this application provide a method for fine evaluation of continuous brittleness index based on scratch testing under true triaxial stress, applied to computer equipment, the method comprising:

[0007] Obtain core samples from the target reservoir;

[0008] Continuous scratch testing was performed on the core samples to obtain multiple mechanical response indicators;

[0009] Based on the mechanical response index, the first calculation process is performed to obtain the rock strength brittleness index;

[0010] Based on the mechanical response index, a second calculation process is performed to obtain the rock deformation brittleness index;

[0011] Based on the mechanical response index, a third calculation process is performed to obtain the energy evolution brittleness index;

[0012] Based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, a comprehensive brittleness index is determined to evaluate the brittleness of the target reservoir shale.

[0013] In one possible implementation, the mechanical response parameters include tangential force and normal force.

[0014] In one possible implementation, the mechanical response index further includes the cross-sectional area of ​​the etched surface. Based on the mechanical response index, a first calculation process is performed to obtain the rock strength brittleness index, including:

[0015] Determine fracture toughness based on tangential force;

[0016] Determine the hardness of the rock based on the normal force;

[0017] The rock strength brittleness index is determined based on the ratio of rock hardness to fracture toughness.

[0018] In one possible implementation, the mechanical response indicators also include scratch depth, scalpel width, total height of the core sample, and total width of the core sample;

[0019] Accordingly, based on the mechanical response index, a second calculation is performed to obtain the rock deformation brittleness index, including:

[0020] Determine Young's modulus based on tangential force and scratch depth;

[0021] Determine Poisson's ratio based on the width of the engraving tool, its total height, its total width, and the depth of the scratch.

[0022] The rock deformation brittleness index is determined based on Young's modulus and Poisson's ratio.

[0023] In one possible implementation, a third calculation is performed based on the mechanical response index to obtain the energy evolution brittleness index, including:

[0024] Calculate the integral of the tangential force to obtain the total energy required to create the scratch;

[0025] Based on the change in tangential force, the sharp abrupt change peak is calculated to extract the brittle energy dissipation.

[0026] Based on the total energy required for scratching and the sharp abrupt change peak, the brittleness energy dissipation is extracted, and the energy evolution brittleness index is calculated.

[0027] In one possible implementation, a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale is determined based on the rock strength brittleness index, the rock deformation brittleness index, and the energy evolution brittleness index, including:

[0028] Based on the mechanical response index, the first entropy weight corresponding to the rock strength brittleness index, the second entropy weight corresponding to the rock deformation brittleness index, and the third entropy weight corresponding to the energy evolution brittleness index are determined respectively.

[0029] The rock strength brittleness index, rock deformation brittleness index, rock deformation brittleness index, third entropy index, and energy evolution brittleness index are weighted to obtain a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale.

[0030] In one possible implementation, after determining the comprehensive brittleness index for evaluating the brittleness of the target reservoir shale based on the rock strength brittleness index, the rock deformation brittleness index, and the energy evolution brittleness index, the method further includes:

[0031] The overall fragility index is sent to a display device for display, and / or the overall fragility index is displayed on a preset display interface.

[0032] Secondly, embodiments of this application provide a fine evaluation device for continuous brittleness index based on scratch testing under true triaxial stress, comprising: a memory and a processor;

[0033] The memory stores the instructions that the computer executes;

[0034] The processor executes computer execution instructions stored in memory, causing the processor to perform the first aspect and / or various possible implementations of the first aspect as described above.

[0035] Thirdly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the first aspect and / or various possible implementations of the first aspect.

[0036] Fourthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.

[0037] This application provides a method, equipment, storage medium, and program product for fine evaluation of continuous brittleness index based on scratch testing under true triaxial stress. The method involves obtaining core samples from the target reservoir; performing continuous scratch testing on the core samples to obtain multiple mechanical response indices; and sequentially calculating and processing these indices to obtain the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, thereby evaluating the comprehensive brittleness index of the target reservoir shale. Compared to existing technologies, this method uses scratch testing to obtain mechanical response indices from shale reservoir samples, calculates and processes these indices to obtain the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, and constructs a high-resolution shale brittleness evaluation method. This achieves millimeter-centimeter-level continuous brittleness characterization of the mechanical properties of the shale laminar-lithological interface, and represents a breakthrough from single-point to continuous evaluation of shale brittleness, thus improving the accuracy of shale brittleness evaluation. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0039] Figure 1 A schematic diagram of a fine evaluation system architecture for continuous brittleness index based on scratch testing under true triaxial stress provided for this application;

[0040] Figure 2 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 1 ;

[0041] Figure 3 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 2 ;

[0042] Figure 4 A schematic diagram of the rock strength brittleness index provided in this application;

[0043] Figure 5 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 3 ;

[0044] Figure 6 A schematic diagram illustrating the relationship between the normal force and the scratch depth provided for this application;

[0045] Figure 7 A schematic diagram of the rock deformation brittleness index provided in this application;

[0046] Figure 8A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 4 ;

[0047] Figure 9 A schematic diagram illustrating the total energy required for scratching, brittle energy dissipation, and additional energy dissipation provided in this application;

[0048] Figure 10 A schematic diagram illustrating the trends of brittle work, extra work, and total work provided for this application;

[0049] Figure 11 A schematic diagram of the energy evolution brittleness index provided in this application;

[0050] Figure 12 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 5 ;

[0051] Figure 13 A schematic diagram of the comprehensive brittleness index provided in this application for evaluating the brittleness of the target reservoir shale;

[0052] Figure 14 A schematic diagram of the structure of the fine evaluation device for continuous brittleness index based on scratch test under true triaxial stress provided in this application;

[0053] Figure 15 A schematic diagram of the structure of the fine evaluation device for continuous brittleness index based on scratch test under true triaxial stress provided in this application.

[0054] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0055] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0056] It should be noted that all data involved in this application are information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant laws, regulations and standards, and corresponding operation portals are provided for users to choose to authorize or refuse.

[0057] Shale oil and gas is an important component of unconventional oil and gas resources, typically stored in reservoirs with low permeability and low porosity, and explored and developed using hydraulic fracturing and horizontal drilling techniques. The core challenge in its exploration and development lies in assessing the fracturability of the reservoir. The shale brittleness index is a key parameter characterizing reservoir fracturability, directly affecting the complexity of the fracture network during hydraulic fracturing. For example, highly brittle shale tends to form network fractures, while low-brittle areas are dominated by single fractures, leading to significant differences in fracturing effectiveness. Therefore, shale reservoir development faces challenges from extreme environments and strong heterogeneity, necessitating the development of new technologies to improve the ability to assess reservoir brittleness.

[0058] Existing technologies for evaluating brittleness include mineral composition methods, elastic parameter methods, and stress-strain methods. Mineral composition methods evaluate brittleness based on the proportion of brittle minerals such as quartz and carbonates, but neglect mechanical response characteristics. Elastic parameter methods invert dynamic Young's modulus and Poisson's ratio from well logging data, but cannot characterize the mechanical abrupt changes in laminae at the millimeter-centimeter level. Stress-strain methods rely on the amount of plastic deformation before rock failure, such as the ratio of residual strength to peak strength, to evaluate brittleness, but typically depend on single-point testing and destructive experiments, resulting in high sample preparation costs and inability to be applied in situ.

[0059] Therefore, existing brittleness assessment methods cannot accurately assess the brittleness of complex shale formations, resulting in insufficient accuracy in shale brittleness assessment.

[0060] To address the aforementioned issues, the core concept of this application is as follows: obtaining core samples from the target reservoir; conducting continuous scratch tests on the core samples to obtain multiple mechanical response indices; and through calculation and processing, obtaining the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index to comprehensively evaluate the overall brittleness index of the shale in the target reservoir, thereby achieving millimeter-centimeter-level continuous brittleness characterization of the mechanical properties of the shale laminar-lithological interface, and improving the accuracy of shale brittleness evaluation from single-point to continuous evaluation.

[0061] Optionally, Figure 1 This application provides a schematic diagram of a system architecture for a fine evaluation of continuous brittleness index based on scratch testing under true triaxial stress. Figure 1 As shown, the architecture of the continuous brittleness index fine evaluation system based on the scratch test under true triaxial stress includes at least one of the following: data acquisition device 101, processing device 102, and display device 103.

[0062] It is understood that the structures illustrated in the embodiments of this application do not constitute a specific limitation on the above architecture. In other feasible embodiments of this application, the above architecture may include more or fewer components than illustrated, or combine some components, or split some components, or arrange different components, which can be determined according to the actual application scenario and is not limited here. Figure 1 The components shown can be implemented in hardware, software, or a combination of both.

[0063] In the specific implementation process, the data acquisition device 101 may include an input / output interface or a communication interface, and the data acquisition device 101 can be connected to the processing device through the input / output interface or the communication interface.

[0064] The processing device 102 can perform continuous scratch tests on core samples to obtain multiple mechanical response indices; based on the mechanical response indices, a first calculation is performed to obtain the rock strength brittleness index; based on the mechanical response indices, a second calculation is performed to obtain the rock deformation brittleness index; based on the mechanical response indices, a third calculation is performed to obtain the energy evolution brittleness index; based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, a comprehensive brittleness index is determined for evaluating the brittleness of the target reservoir shale, thereby improving the accuracy of shale brittleness evaluation.

[0065] The display device 103 can also be a touch screen or the screen of a terminal device, used to receive user commands while displaying the above-mentioned content, so as to realize interaction with the user.

[0066] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0067] Figure 2 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 1 ,like Figure 2 As shown, the method includes:

[0068] S201. Obtain core samples from the target reservoir.

[0069] In this embodiment, the core sample refers to a cylindrical rock specimen obtained directly from the target reservoir using drilling coring technology.

[0070] Obtaining core samples from the target reservoir includes:

[0071] Full-diameter core samples were extracted from underground reservoirs using well core drilling technology.

[0072] Core samples from the target reservoir were cut along the direction perpendicular to the laminae to obtain cut core samples for subsequent analysis and observation. The surface dimensions of the cut core samples were 100mm × 80mm × 70mm, and the cut core samples had smooth, flat surfaces and were elongated.

[0073] Furthermore, the lithology, lithological interfaces, and lamination distribution of the core samples were calibrated to determine the rock type, contact surfaces between different lithologies, and lamination distribution of the core samples.

[0074] S202. Perform continuous scratch tests on the core samples to obtain multiple mechanical response indicators.

[0075] In this embodiment, a scratch testing device is used to perform scratch testing on the cut core sample based on a continuous multi-point scratching method with equal spacing. The scratch test refers to the scratching knife scratching the cut core sample at a constant scratching rate and depth, and the displacement and force data of the scratching knife are recorded in real time to obtain multiple mechanical response indicators; the constant scratching depth is controlled within the millimeter range.

[0076] For example, the parameters for the scratch testing equipment are set as shown in the table below:

[0077]

[0078] Optionally, the mechanical response parameters include tangential force and normal force.

[0079] In this embodiment, tangential force refers to the force parallel to the surface of the core sample, and normal force refers to the force perpendicular to the surface of the core sample; the calculation formulas for tangential force and normal force are as follows:

[0080]

[0081]

[0082]

[0083] In the formula, F s F is the tangential force, measured in N. n Normal force, measured in N; The specific work of rock fracturing is expressed in MPa. ρ is the ratio of normal stress to shear stress; w is the width of the engraving tool in mm; h is the engraving depth in mm; A is the cross-sectional area of ​​the engraved surface in mm². 2 .

[0084] S203. Based on the mechanical response index, perform the first calculation process to obtain the rock strength brittleness index.

[0085] In this embodiment, the rock strength brittleness index is an indicator that quantifies the brittle characteristics of rocks during stress failure. The higher the rock strength brittleness index, the easier the rock is to fracture, making it suitable for reservoir stimulation; the lower the rock strength brittleness index, the stronger the rock's plasticity, resulting in poor fracturing effect. By performing the first calculation based on the mechanical response index, the rock strength brittleness index is obtained, and corresponding mining strategies can be formulated to improve mining efficiency.

[0086] S204. Based on the mechanical response index, a second calculation process is performed to obtain the rock deformation brittleness index.

[0087] In this embodiment, the rock deformation brittleness index is an indicator that quantifies the brittle characteristics of rocks during stress deformation. It is used to describe the transition of rocks from elastic deformation to plastic deformation and reflects the rock reservoir's ability to release instability. Based on the mechanical response index, a second calculation is performed to obtain the rock deformation brittleness index, which can assess the deformation capacity and failure mode of rocks under different stress conditions, predict rock mass deformation, and design stable underground structures, thereby improving the reliability of mining.

[0088] S205. Based on the mechanical response index, a third calculation process is performed to obtain the energy evolution brittleness index.

[0089] In this embodiment, the energy evolution brittleness index is a quantification of brittleness by measuring the balance between energy accumulation and dissipation during rock deformation and failure. Based on the mechanical response index, a third calculation is performed to obtain the energy evolution brittleness index, which can predict the potential risks of rock failure and the scale of energy release, thereby enabling proactive response strategies.

[0090] S206. Based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, determine the comprehensive brittleness index used to evaluate the brittleness of the target reservoir shale.

[0091] In this embodiment, a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale is determined by combining the rock strength brittleness index, the rock deformation brittleness index, and the energy evolution brittleness index. This constructs a high-resolution shale brittleness evaluation system, achieving continuous brittleness characterization of shale laminae and lithological interface mechanical properties at the millimeter to centimeter level, thereby improving the accuracy of shale brittleness evaluation.

[0092] This application provides a refined evaluation method for continuous brittleness index based on scratch testing under true triaxial stress. By processing core samples and performing millimeter-resolution scratch tests, mechanical response indices are obtained. The rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index are then calculated sequentially to determine the comprehensive brittleness index used to evaluate the brittleness of the target shale reservoir. This method reduces sample requirements, improves scratch testing efficiency, and achieves continuous brittleness characterization of shale laminae and lithological interfaces at the millimeter to centimeter level. It breaks through the limitations of single-point to continuous evaluation of shale brittleness, constructs a high-resolution shale brittleness evaluation system, provides a reliable geomechanical model for the differentiated parameter design of hydraulic fracturing in shale reservoirs, meets the practicality and efficiency requirements of engineering applications, and provides a basis for improving the benefits of complex reservoir stimulation.

[0093] Figure 3 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 2 ,like Figure 3 As shown, the mechanical response index also includes the cross-sectional area of ​​the etched surface; in this embodiment... Figure 2 Based on the embodiments, the method of performing a first calculation based on the mechanical response index to obtain the rock strength brittleness index in step S203 above will be described in detail. The method includes:

[0094] S301. Determine the fracture toughness based on the tangential force.

[0095] In this embodiment, the calculation formula for determining the fracture toughness of rock based on tangential force and normal force is as follows:

[0096] In the formula, Fracture toughness, unit: ;F s F is the tangential force, measured in N. n Normal force, measured in N; The width of the engraving tool is in mm. The depth of the incision is expressed in mm.

[0097] S302. Determine the hardness of the rock based on the normal force.

[0098]

[0099] In the formula, Rock hardness, in N / mm 2 , The cross-sectional area of ​​the scribed surface is expressed in mm. 2 .

[0100] S303. Determine the rock strength brittleness index based on the ratio of rock hardness to fracture toughness.

[0101] In this embodiment, the formula for calculating the rock strength brittleness index is as follows:

[0102] In the formula, BI ct The rock strength brittleness index; The hardness of the rock; This refers to fracture toughness.

[0103] For example, the rock strength brittleness index is as follows: Figure 4 As shown.

[0104] The continuous brittleness index fine evaluation method based on true triaxial stress scratch test provided in this application determines the rock strength brittleness index by determining the fracture toughness and rock hardness, effectively assessing the brittleness of the rock and thus optimizing resource mining strategies.

[0105] Figure 5 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 3 ,like Figure 5 As shown, the mechanical response indicators also include scratch depth, burr width, total height of the core sample, and total width of the core sample; this embodiment... Figure 2 Based on the embodiments, the second calculation process in step S204 above, which involves performing a second calculation based on the mechanical response index to obtain the rock deformation brittleness index, is described in detail. This method includes:

[0106] S501. Determine Young's modulus based on tangential force and scratch depth.

[0107] In this embodiment, the formula for calculating Young's modulus is as follows:

[0108]

[0109] In the formula, E is Young's modulus; F S Δ is the tangential force, in N; h is the marking depth, in mm.

[0110] S502. Determine Poisson's ratio based on the engraving tool width, total height, total width, and scratch depth.

[0111] In this embodiment, the formula for calculating Poisson's ratio is as follows:

[0112]

[0113] In the formula, v is Poisson's ratio; W is the total width of the core sample; H is the total height of the core sample; and h is the indentation depth. This represents the change in the width of the engraving tool, which is the difference between the width of the engraving tool after the core sample is deformed by force and the original width of the engraving tool.

[0114] S503. Determine the rock deformation brittleness index based on Young's modulus and Poisson's ratio.

[0115] In this embodiment, the formula for calculating the rock deformation brittleness index is as follows:

[0116]

[0117] In the formula, BI Y E is the rock deformation brittleness index; E is Young's modulus; E min E is the minimum value of Young's modulus. max v is the maximum value of Young's modulus; v is Poisson's ratio; v max This represents the maximum value of Poisson's ratio; v min This is the minimum value of Poisson's ratio.

[0118] For example, in this embodiment, the relationship between the normal force and the scratch depth in the scratch test is as follows: Figure 6 As shown, the rock deformation brittleness index is as follows: Figure 7 As shown.

[0119] The continuous brittleness index evaluation method based on true triaxial stress scratch test provided in this application determines Young's modulus based on tangential force and scratch depth; determines Poisson's ratio based on cutter width, total height, total width, and scratch depth; and determines the rock deformation brittleness index based on Young's modulus and Poisson's ratio. This method accurately assesses the elastic characteristics of rocks and predicts their deformation behavior, enabling the development of corresponding mining strategies and improving the safety and stability of underground structures.

[0120] Figure 8 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 4 ,like Figure 8 As shown, the mechanical response indicators also include scratch depth, burr width, total height of the core sample, and total width of the core sample; this embodiment... Figure 2 Based on the embodiments, the third calculation process in step S205 above, which involves performing calculations based on mechanical response indices to obtain the energy evolution brittleness index, is described in detail. This method includes:

[0121] S801. Calculate the integral of the tangential force to obtain the total energy required for the scratch.

[0122] In this embodiment, the tangential force varies with the scratch depth. After calculating the rock strength brittleness index and rock deformation brittleness index of the core sample based on the tangential force obtained from continuous scratch testing, since brittle materials accumulate strain energy through elastic deformation and rapidly release most of the energy upon failure, while ductile materials have limited strain energy reservoir force and gradually dissipate energy through plastic deformation, the total energy required for scratching can be calculated by integrating the tangential force. The formula for calculating the total energy required for scratching is as follows:

[0123]

[0124] In the formula, W S The total energy required to create the scratch; L is the maximum scratch depth; x is the scratch depth; F s For tangential force; F s (x) represents the relationship between tangential force and scratch depth.

[0125] S802. Based on the change value of tangential force, the sharp abrupt peak is calculated to extract the brittle energy dissipation.

[0126] In this embodiment, during the scratch test, the core sample accumulates high strain energy during the elastic deformation stage. After the accumulated strain energy reaches its peak, the core sample breaks down, and the crack propagates, rapidly releasing energy. Therefore, brittle energy dissipation can be determined by obtaining the sharp abrupt peak in the tangential force change value. The calculation formula for brittle energy dissipation is as follows:

[0127]

[0128] In the formula, W B It is brittle and energy-consuming; For the xth i The tangential force corresponding to the nth point and the nth The difference in tangential force corresponding to each point; i is the scratch depth indicator; x is the scratch depth.

[0129] Furthermore, such as Figure 9 As shown, the total energy required for scratching is the sum of brittle energy dissipation and additional energy dissipation. Brittle work measures the change in brittle energy dissipation, additional work measures the additional energy dissipation, and total work measures the total energy required for scratching. The trends of brittle work, additional work, and total work are shown below. Figure 10 As shown.

[0130] S803. Based on the total energy required for scratching and the sharp abrupt change peak, extract the brittle energy dissipation and calculate the energy evolution brittleness index.

[0131] In this embodiment, the formula for calculating the energy evolution brittleness index is as follows:

[0132]

[0133] In the formula, BI W W is the energy evolution brittleness index. S The total energy required to scratch; W B It is a brittle energy-consuming process.

[0134] For example, the energy evolution fragility index, such as Figure 11 As shown.

[0135] The continuous brittleness index fine evaluation method based on scratch test under true triaxial stress provided in this application obtains the total energy required for scratching by calculating the integral of tangential force; extracts brittle energy dissipation by calculating sharp abrupt peaks based on the change value of tangential force; and calculates the energy evolution brittleness index based on the total energy required for scratching and the brittle energy dissipation extracted by sharp abrupt peaks. Thus, it predicts the dynamic energy change of rocks under different conditions to optimize engineering design.

[0136] Figure 12 A flowchart illustrating the fine evaluation method for the continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 5 ,like Figure 12 As shown, the mechanical response indicators also include scratch depth, burr width, total height of the core sample, and total width of the core sample; this embodiment... Figure 2 Based on the embodiments, the method for determining the comprehensive brittleness index used to evaluate the brittleness of the target reservoir shale in step S206 above, based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, is described in detail. The method includes:

[0137] S1201. Based on the mechanical response index, determine the first entropy weight corresponding to the rock strength brittleness index, the second entropy weight corresponding to the rock deformation brittleness index, and the third entropy weight corresponding to the energy evolution brittleness index.

[0138] In this embodiment, the calculation formulas for the first entropy weight corresponding to the rock strength brittleness index, the second entropy weight corresponding to the rock deformation brittleness index, and the third entropy weight corresponding to the energy evolution brittleness index are as follows:

[0139]

[0140]

[0141] In the formula, u j Let be the entropy weight of the j-th evaluation index; i is the evaluation index identifier; j is the parameter identifier; b ij Let q be the j-th parameter of the i-th evaluation index; ij is the entropy value of the j-th parameter of the i-th evaluation index; m is the number of core samples; n is the total number of evaluation indexes.

[0142] In this embodiment, when j is 1, u1 is the first entropy weight corresponding to the rock strength brittleness index; when j is 2, u2 is the second entropy weight corresponding to the rock deformation brittleness index; and when j is 3, u3 is the third entropy weight corresponding to the energy evolution brittleness index.

[0143] S1202. Based on the first entropy weight, rock strength brittleness index, second entropy weight, rock deformation brittleness index, third entropy weight, and energy evolution brittleness index, a weighted average is performed to obtain a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale.

[0144] In this embodiment, the formula for calculating the comprehensive brittleness index used to evaluate the brittleness of the target reservoir shale is as follows:

[0145]

[0146] In the formula, BI is the comprehensive brittleness index; u1 is the first entropy weight; rock strength brittleness index; u2 is the second entropy weight; BI ct is the rock deformation brittleness index; u3 is the third entropy weight; BI W U is the energy evolution fragility index; where u1, u2, and u3 are the weight vectors U = (u1, u2, u3). T A subset of u1, u2 and u3, and the sum of u1, u2 and u3 is 1.

[0147] For example, the first entropy weight can be 0.2, the second entropy weight can be 0.3, and the third entropy weight can be 0.5. Then, the comprehensive brittleness index used to evaluate the brittleness of the target reservoir shale is as follows: Figure 13 As shown.

[0148] Optionally, after determining the comprehensive brittleness index for evaluating the brittleness of the target reservoir shale based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index, the method further includes:

[0149] S1203. Send the comprehensive fragility index to the display device for display, and / or display the comprehensive fragility index on a preset display interface.

[0150] The continuous brittleness index fine evaluation method based on scratch test under true triaxial stress provided in this application integrates the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index; and calculates the corresponding first entropy weight, second entropy weight, and third entropy weight, and performs appropriate weighting to obtain a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale. The weighting is based on the dispersion of the data itself to avoid errors, thereby improving the accuracy of the comprehensive brittleness index.

[0151] Figure 14 A schematic diagram of the structure of the fine evaluation device for continuous brittleness index based on scratch testing under true triaxial stress provided in this application is shown below. Figure 14 As shown, the fine evaluation device for continuous brittleness index based on scratch testing under true triaxial stress provided in this embodiment includes:

[0152] The acquisition module 1401 is used to acquire core samples from the target reservoir.

[0153] Test module 1402 is used to perform continuous scratch tests on core samples to obtain multiple mechanical response indicators.

[0154] Optionally, the mechanical response parameters include tangential force and normal force.

[0155] The first calculation module 1403 is used to perform a first calculation process based on the mechanical response index to obtain the rock strength brittleness index.

[0156] The second calculation module 1404 is used to perform a second calculation process based on the mechanical response index to obtain the rock deformation brittleness index.

[0157] The third calculation module 1405 is used to perform a third calculation based on the mechanical response index to obtain the energy evolution brittleness index.

[0158] The determination module 1406 is used to determine the comprehensive brittleness index for evaluating the brittleness of the target reservoir shale based on the rock strength brittleness index, rock deformation brittleness index, and energy evolution brittleness index.

[0159] In one possible implementation, the mechanical response index also includes the cross-sectional area of ​​the etched surface; the first calculation module 1403 can also be used specifically for:

[0160] Fracture toughness is determined based on tangential force; rock hardness is determined based on normal force.

[0161] The rock strength brittleness index is determined based on the ratio of rock hardness to fracture toughness.

[0162] In one possible implementation, the mechanical response indicators also include scratch depth, burr width, total height of the core sample, and total width of the core sample; the second calculation module 1404 can also be used specifically for:

[0163] Determine Young's modulus based on tangential force and scratch depth;

[0164] Determine Poisson's ratio based on the width of the engraving tool, its total height, its total width, and the depth of the scratch.

[0165] The rock deformation brittleness index is determined based on Young's modulus and Poisson's ratio.

[0166] In one possible implementation, the third computing module 1405 can also be used for:

[0167] Calculate the integral of the tangential force to obtain the total energy required to create the scratch;

[0168] Based on the change in tangential force, the sharp abrupt change peak is calculated to extract the brittle energy dissipation.

[0169] Based on the total energy required for scratching and the sharp abrupt change peak, the brittleness energy dissipation is extracted, and the energy evolution brittleness index is calculated.

[0170] In one possible implementation, the determining module 1406 can also be used for:

[0171] Based on the mechanical response index, the first entropy weight corresponding to the rock strength brittleness index, the second entropy weight corresponding to the rock deformation brittleness index, and the third entropy weight corresponding to the energy evolution brittleness index are determined respectively.

[0172] The rock strength brittleness index, rock deformation brittleness index, rock deformation brittleness index, third entropy index, and energy evolution brittleness index are weighted to obtain a comprehensive brittleness index for evaluating the brittleness of the target reservoir shale.

[0173] In one possible implementation, after determining the comprehensive brittleness index used to evaluate the brittleness of the target reservoir shale based on the rock strength brittleness index, the rock deformation brittleness index, and the energy evolution brittleness index, the method further includes:

[0174] The display module is used to send the comprehensive fragility index to the display device for display, and / or to display the comprehensive fragility index on a preset display interface.

[0175] The fine evaluation device for continuous brittleness index based on scratch test under true triaxial stress provided in this embodiment can perform the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0176] Figure 15 This is a schematic diagram of the structure of the fine evaluation device for continuous brittleness index based on scratch testing under true triaxial stress provided in this application. Figure 15 As shown, the fine evaluation device for continuous brittleness index based on true triaxial stress scratch test provided in this embodiment includes at least one processor 1501 and a memory 1502. Optionally, the fine evaluation device for continuous brittleness index based on true triaxial stress scratch test further includes a communication component 1503. The processor 1501, memory 1502, and communication component 1503 are connected via a bus 1504.

[0177] In a specific implementation, at least one processor 1501 executes computer execution instructions stored in memory 1502, causing at least one processor 1501 to perform the above-described method.

[0178] The specific implementation process of processor 1501 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0179] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0180] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0181] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0182] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0183] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0184] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0185] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0186] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0187] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0188] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0189] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0190] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0191] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for fine evaluation of continuous brittleness index based on scratch testing under true triaxial stress, characterized in that, Applied to a computer device, the method includes: Obtain core samples from the target reservoir; The core sample was subjected to continuous scratch testing to obtain multiple mechanical response indicators, including tangential force, normal force, and cross-sectional area of ​​the scratched surface. Based on the tangential force and the normal force, the fracture toughness is determined according to formula (1): （1） in, The fracture toughness is given in units of... ;F s The tangential force is expressed in N; F n The normal force is expressed in N. The width of the engraving tool is in mm. The depth of the scratch is expressed in mm. The hardness of the rock is determined based on the normal force. Based on the ratio of the rock's hardness to its fracture toughness, the rock's strength-brittleness index is determined using formula (2): （2） Among them, BI ct The rock strength brittleness index; The hardness of the rock; The fracture toughness is mentioned above; The mechanical response indicators also include scratch depth, scalpel width, total height of the core sample, and total width of the core sample; Young's modulus is determined based on the tangential force and the scratch depth; The Poisson's ratio is determined based on the engraving blade width, the total height, the total width, and the scratch depth. Based on the Young's modulus and the Poisson's ratio, the deformation brittleness index of the rock is determined according to formula (3): （3） Among them, BI Y E is the deformation brittleness index of the rock; E is the Young's modulus; E min E is the minimum value of the Young's modulus. max v is the maximum value of Young's modulus; v is the Poisson's ratio; v max v is the maximum value of the Poisson's ratio; min This is the minimum value of the Poisson's ratio; Calculate the integral of the tangential force to obtain the total energy required to scratch the surface; Based on the change in tangential force, the brittle energy dissipation extracted from the sharp abrupt change peak is calculated; Based on the total energy required for the scratch and the brittle energy dissipation extracted from the sharp abrupt change peak, the energy evolution brittleness index is calculated using formula (4): （4） Among them, BI W W is the energy evolution brittleness index; S The total energy required to create the scratch; W B For the aforementioned brittle energy dissipation; Based on the mechanical response index, the first entropy weight corresponding to the rock strength brittleness index, the second entropy weight corresponding to the rock deformation brittleness index, and the third entropy weight corresponding to the energy evolution brittleness index are determined respectively. The target reservoir's comprehensive brittleness index is obtained by weighting the first entropy weight, the rock strength brittleness index, the second entropy weight, the rock deformation brittleness index, the third entropy weight, and the energy evolution brittleness index, in order to evaluate the shale brittleness of the target reservoir.

2. The method according to claim 1, characterized in that, After determining the comprehensive brittleness index for evaluating the brittleness of the target reservoir shale based on the rock strength brittleness index, the rock deformation brittleness index, and the energy evolution brittleness index, the method further includes: The comprehensive fragility index is sent to a display device for display, and / or the comprehensive fragility index is displayed on a preset display interface.

3. A fine evaluation device for continuous brittleness index based on scratch testing under true triaxial stress, characterized in that, include: Memory, processor; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory, causing the processor to perform the method as described in any one of claims 1-2.

4. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-2.

5. A computer program product, characterized in that, Includes a computer program that, when executed by a processor, implements the method as described in any one of claims 1-2.

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