A rock brittleness index calculation method, system, electronic device and storage medium

Abstract

The present disclosure relates to the technical field of oil and gas exploration reservoir evaluation, and a rock brittleness index calculation method, system, electronic device and storage medium, the method comprising: performing triaxial compression test based on rock to obtain a stress-strain curve; calculating a pre-peak brittleness index based on the stress-strain curve; calculating a post-peak brittleness index based on the stress-strain curve; and calculating a rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index. The energy evolution characteristics of the whole process of rock deformation from the beginning to failure under external force can be reflected based on the stress-strain curve of rock triaxial compression test, and the brittleness evaluation index is established, and the brittleness influencing factors of rock lithology, diagenesis, confining pressure and pore pressure are comprehensively considered, the brittleness change trend of the whole range of rock from ideal plasticity to ideal brittleness is continuously measured, and the accuracy of rock brittleness index calculation can be improved.

Description

Technical Field

[0001] This disclosure relates to the field of oil and gas exploration reservoir evaluation technology, and in particular to a method, system, electronic device and storage medium for calculating rock brittleness index. Background Technology

[0002] Brittleness characterizes the ability of rocks to resist inelastic deformation before failure and to sustain macroscopic failure after failure. In oil and gas exploration and development, brittleness is an important parameter for evaluating the degree of natural fracture development and predicting the effectiveness of hydraulic fracturing. Reservoirs with higher brittleness are more likely to develop natural tectonic fractures and are more likely to form complex fracture systems during hydraulic fracturing.

[0003] Currently, the method for evaluating the brittleness of rocks uses the stress-strain curve method to obtain the strength parameters of rock samples and quantitatively evaluate the brittleness of the rock samples. However, this method lacks consideration of various brittleness-influencing factors such as rock lithology, diagenesis, confining pressure, and pore pressure when determining the rock brittleness index. It also lacks analysis and evaluation of the stress-strain curve of the rock sample based on brittleness-influencing factors, which can easily affect the accuracy of the rock brittleness index calculation. Summary of the Invention

[0004] To address the aforementioned issues, this disclosure provides a method, system, electronic device, and storage medium for calculating the rock brittleness index. Based on the energy evolution characteristics of rock under external force, as reflected by the stress-strain curve of a triaxial compression test, a brittleness evaluation index is established. This index comprehensively considers various brittleness influencing factors, including lithology, diagenesis, confining pressure, and pore pressure. It can continuously measure the brittleness variation trend of rock across the entire range from ideal plasticity to ideal brittleness, thereby improving the accuracy of rock brittleness index calculation.

[0005] The first aspect of this disclosure provides a method for calculating the brittleness index of rock, comprising: conducting a triaxial compression test on the rock to obtain a stress-strain curve; calculating a pre-peak brittleness index based on the stress-strain curve; calculating a post-peak brittleness index based on the stress-strain curve; and calculating a rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index.

[0006] This setup, after obtaining the stress-strain curve, calculates the rock's brittleness index based on the pre-peak and post-peak brittleness indices on the curve. This ensures that both the pre- and post-peak portions of the curve are included in the calculation, allowing for the consideration of brittleness-influencing factors such as lithology, diagenesis, confining pressure, and pore pressure by combining pre- and post-peak data. A brittleness evaluation index is established based on the entire process of rock deformation and failure under external force, which can realistically reflect the rock's failure process. This helps to continuously measure the brittleness variation trend of rocks across the entire range from ideal plasticity to ideal brittleness, thereby improving the accuracy of rock brittleness index calculation.

[0007] In some embodiments, the triaxial compression test based on rock to obtain stress-strain curves includes: the triaxial compression test includes applying axial pressure to two sections of the rock; and obtaining stress-strain curves of the rock as the axial pressure gradually increases until the rock fractures.

[0008] This setup is designed to simulate the actual underground environment in which rocks exist, which helps to obtain the stress-strain curves of the rocks.

[0009] In some embodiments, the triaxial compression test based on rock to obtain the stress-strain curve includes: the vertical axis of the stress-strain curve is the principal stress difference, and the horizontal axis is the axial strain.

[0010] This setup helps to obtain the relationship curve between principal stress and axial strain.

[0011] In some embodiments, the triaxial compression test based on rock to obtain the stress-strain curve includes: the stress-strain curve having the zero point, yield strength point, peak strength point and residual strength point corresponding to the principal stress difference and axial strain.

[0012] This setup facilitates marking points on the stress-strain curve, which helps in analyzing the axial and confining pressures per unit area of ​​the rock's circular cross-section at each point.

[0013] In some embodiments, the stress-strain curve having zero points, yield strength points, peak strength points, and residual strength points corresponding to the principal stress difference and axial strain includes: the stress-strain curve being a straight line between the zero point and the yield strength point, and the principal stress difference increasing with the increase of the axial strain.

[0014] This setting indicates that the rock undergoes only elastic deformation during the process, and the principal stress difference increases with the increase of axial strain, which helps to determine the yield strength point as the boundary point between the straight line and the curve of the stress-strain curve.

[0015] In some embodiments, the stress-strain curve having zero points, yield strength points, peak strength points, and residual strength points corresponding to the principal stress difference and axial strain includes: the stress-strain curve being a curve between the yield strength point and the peak strength point, and the principal stress difference increasing with the increase of the axial strain.

[0016] This setting indicates that the rock undergoes both elastic and plastic deformation during the process, and the principal stress difference increases with the increase of axial strain. This helps to determine the peak strength point, which is the point where the principal stress difference increases to its maximum value with the increase of axial strain.

[0017] In some embodiments, the stress-strain curve having zero points, yield strength points, peak strength points, and residual strength points corresponding to the principal stress difference and axial strain includes: the stress-strain curve being a curve between the peak strength point and the residual strength point, and the principal stress difference decreasing as the axial strain increases.

[0018] This setting indicates that the rock undergoes both elastic and plastic deformation during the process, and the principal stress difference decreases as the axial strain increases. This helps to determine the residual strength point, which is the point where the principal stress difference decreases to its minimum as the axial strain increases.

[0019] In some embodiments, the triaxial compression test based on rock to obtain a stress-strain curve includes: determining the principal stress difference and axial strain of the yield strength point, peak strength point, and residual strength point based on the shape of the stress-strain curve between two specific points.

[0020] This setup helps to assess the rock's ability to resist plastic deformation, i.e., yield strength; helps to assess the maximum load-bearing capacity, i.e., peak strength; and helps to assess the portion that can maintain stability before fracture, i.e., residual strength.

[0021] In some embodiments, the triaxial compression test on the rock to obtain the stress-strain curve includes: obtaining the elastic modulus of the rock based on the principal stress difference and axial strain at the yield strength point; the elastic modulus is calculated using the following formula:

[0022]

[0023] In the formula, E is the elastic modulus of the rock, with units of MPa; σ a ε is the principal stress difference at the yield strength point, in MPa; a The axial strain at the yield strength point is dimensionless.

[0024] This setup helps to calculate the principal stress difference required to generate a unit axial strain in the rock based on the principal stress difference at the yield strength point and the axial strain.

[0025] In some embodiments, the calculation of the pre-peak brittleness index based on the stress-strain curve includes: calculating the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point based on the stress-strain curve.

[0026] The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point is calculated by the following formula:

[0027]

[0028] In the formula, Wea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 ;σ a ρ represents the principal stress difference at the yield strength point, in MPa; E represents the elastic modulus of the rock, in MPa.

[0029] This setup allows us to characterize the elastic deformation energy of the rock at its yield strength point.

[0030] In some embodiments, the calculation of the pre-peak brittleness index based on the stress-strain curve includes: calculating the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point based on the stress-strain curve.

[0031] The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point is calculated by the following formula:

[0032]

[0033] In the formula, W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 ;σ b denoted as the principal stress difference at the peak strength point, in MPa; E is the elastic modulus of the rock, in MPa.

[0034] This setup allows us to characterize the elastic deformation energy of the rock at its peak strength point.

[0035] In some embodiments, calculating the pre-peak brittleness index based on the stress-strain curve includes: calculating the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point based on the stress-strain curve;

[0036] The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point is calculated by the following formula:

[0037]

[0038] In the formula, W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 ;ε a ε is the axial strain at the yield strength point, dimensionless; bσ is the axial strain at the peak strength point, dimensionless; σ is the principal stress difference of the stress-strain curve, in MPa; ε is the axial strain of the stress-strain curve, dimensionless.

[0039] This setup can characterize the total energy that the rock gains from its yield strength point to its peak strength point through the axial pressure difference.

[0040] In some embodiments, the calculation of the pre-peak brittleness index based on the stress-strain curve includes: calculating the pre-peak brittleness index based on the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, and the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point.

[0041] With this setup, by calculating the pre-peak brittleness index, the greater the ratio of the difference in elastic deformation energy from the yield strength point to the peak strength point to the total energy acquired by the rock from the yield strength point to the peak strength point through the axial pressure difference during the pre-peak stage, the stronger the rock brittleness.

[0042] In some embodiments, the pre-peak brittleness index based on the stress-strain curve is calculated using the following formula:

[0043]

[0044] In the formula, B pre The pre-peak brittleness index is expressed as a percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 W ea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 .

[0045] This setting helps in calculating the pre-peak brittleness index based on the rock stress-strain curve.

[0046] In some embodiments, calculating the post-peak brittleness index based on the stress-strain curve includes: calculating the energy sum based on the stress-strain curve;

[0047] The energy is calculated using the following formula:

[0048]

[0049] In the formula, W g The sum of energy, in units of 10. 6 J / m 3 ;ε b ε represents the axial strain at the peak strength point, which is dimensionless. c σ is the axial strain at the residual strength point, dimensionless; σ is the principal stress difference of the stress-strain curve, in MPa; ε is the axial strain of the stress-strain curve, dimensionless; b denoted as the principal stress difference at the peak strength point, in MPa; E is the elastic modulus of the rock, in MPa.

[0050] This configuration can characterize the sum of the total energy gained by the rock from the peak strength point to the residual strength point through the axial pressure difference and the elastic deformation energy of the rock at the peak strength point.

[0051] In some embodiments, calculating the post-peak brittleness index based on the stress-strain curve includes: the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, and the energy used to calculate the post-peak brittleness index.

[0052] With this setting, by calculating the post-peak brittleness index, the greater the ratio of the elastic deformation energy of the rock at the peak strength point to the total energy obtained by the rock from the peak strength point to the residual strength point through the axial pressure difference and the sum of the elastic deformation energy of the rock at the peak strength point, the stronger the rock brittleness.

[0053] In some embodiments, the elastic strain energy provided by the axial pressure difference per unit volume of rock based on the peak strength point, as well as the energy and the post-peak brittleness index, are calculated using the following formula:

[0054]

[0055] In the formula, B post Post-peak brittleness index, in percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 W g The sum of energy, in units of 10. 6 J / m 3 .

[0056] This setting helps in calculating the post-peak brittleness index based on the rock stress-strain curve.

[0057] In some embodiments, calculating the rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index includes: the rock brittleness index is calculated using the following formula:

[0058]

[0059] In the formula, B is the rock brittleness index, expressed as a percentage (%). pre B is the pre-peak brittleness index, expressed as a percentage. post Post-peak fragility index, expressed as a percentage.

[0060] This setup establishes a brittleness evaluation index based on the entire process of rock deformation and failure under external force. It can realistically reflect the rock failure process and fully consider the changes in rock brittleness before and after the peak. It helps to calculate the brittleness index of rock based on the rock stress-strain curve combined with the pre-peak brittleness index and the post-peak brittleness index.

[0061] A second aspect of this disclosure provides a rock brittleness index calculation system, the system comprising: a curve generation module for obtaining a rock and performing a triaxial compression test on the rock to obtain a stress-strain curve; a pre-peak brittleness index module for calculating a pre-peak brittleness index based on the stress-strain curve; a post-peak brittleness index module for calculating a post-peak brittleness index based on the stress-strain curve; and a rock brittleness index module for calculating a rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index.

[0062] The technical effects of any possible implementation of the second aspect can be found in the technical effects of the first aspect mentioned above, and will not be repeated here.

[0063] A third aspect of this disclosure provides an electronic device, the electronic device comprising: a memory for storing a computer program; and a processor for executing the computer program to implement a rock brittleness index calculation method as described in the first aspect.

[0064] The technical effects of any possible implementation of the third aspect can be found in the technical effects of the first aspect mentioned above, and will not be repeated here.

[0065] The fourth aspect of this disclosure provides a computer storage medium storing a computer program that, when executed by a processor, implements a rock brittleness index calculation method as described in the first aspect.

[0066] The technical effects of any possible implementation of the fourth aspect can be found in the technical effects of the first aspect mentioned above, and will not be repeated here.

[0067] Compared with the prior art, this disclosure has the following advantages:

[0068] Brittleness evaluation indexes are established based on the energy evolution characteristics of rock from the initial deformation to failure under external force, as reflected by the stress-strain curves of triaxial compression tests.

[0069] It can comprehensively consider multiple factors affecting the brittleness of rocks, such as lithology, diagenesis, confining pressure, and pore pressure; it can continuously measure the brittleness trend of rocks across the entire range from ideal plasticity to ideal brittleness, thereby improving the accuracy of rock brittleness index calculation.

[0070] Other features and advantages of this disclosure will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the disclosure. The objects and other advantages of this disclosure may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0072] Figure 1 A flowchart of a method for calculating the brittleness index of rock provided in this embodiment of the present disclosure;

[0073] Figure 2 Stress-strain curves of rocks provided in embodiments of this disclosure;

[0074] Figure 3 A structural block diagram of a rock brittleness index calculation system provided in this embodiment of the disclosure;

[0075] Figure 4 This is a structural block diagram of an electronic device provided in an embodiment of the present disclosure. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0077] See Figure 1 , Figure 1 A flowchart of a rock brittleness index calculation method provided in this disclosure embodiment is shown. The method includes the following steps:

[0078] S100, triaxial compression tests were conducted on rock to obtain stress-strain curves.

[0079] In this embodiment, the reservoir rock needs to be obtained first, which can be done by core drilling. Then, triaxial compression tests are performed on the reservoir rock to obtain stress-strain curves.

[0080] In some embodiments, the triaxial compression test includes applying axial pressure to two sections of the rock and obtaining stress-strain curves of the rock as the axial pressure gradually increases until the rock fractures.

[0081] For example, see Figure 2 , Figure 2 This is a stress-strain curve of the rock provided in an embodiment of this disclosure. The rock to be tested is processed into a cylindrical rock sample, and a predetermined confining pressure and pore pressure are applied to the rock sample. For example, the diameter of the rock sample is 2.500 cm and the length is 5.864 cm. The confining pressure is 25 MPa and the pore pressure is 15 MPa. By applying the confining pressure and pore pressure to the rock sample, the actual underground environment in which the rock sample exists can be simulated. Axial pressure is applied to two cross-sections of the cylindrical rock sample and gradually increased until the rock sample fractures. Simultaneously, the stress-strain curve of the rock sample during the change of axial pressure is obtained.

[0082] It should be noted that the stress-strain curve uses the principal stress difference as the ordinate and the axial strain as the abscissa. The stress-strain curve is used to characterize the relationship between the principal stress difference and the axial strain of the rock. The principal stress difference is the difference between the axial pressure and the confining pressure per unit area of ​​the circular cross-section of a cylindrical rock sample.

[0083] In some embodiments, the stress-strain curve has zero points, yield strength points, peak strength points, and residual strength points corresponding to the principal stress difference and axial strain. That is, based on the linear shape of the stress-strain curve between two specific points, the yield strength point, peak strength point, and residual strength point of the rock can be determined from the stress-strain curve. These two specific points include: the point where the axial strain is zero and the yield strength point; the yield strength point and the peak strength point; and the peak strength point and the residual strength point. Furthermore, the principal stress difference and axial strain of the rock at the yield strength point, peak strength point, and residual strength point under predetermined test conditions can be read from the stress-strain curve.

[0084] For example, a stress-strain curve that is a straight line between the point where axial strain is zero and the yield strength point indicates that the rock undergoes only elastic deformation during this process, and the principal stress difference increases with increasing axial strain. A stress-strain curve that is a curve between the yield strength point and the peak strength point indicates that the rock undergoes both elastic and plastic deformation during this process, and the principal stress difference increases with increasing axial strain. A stress-strain curve that is a curve between the peak strength point and the residual strength point indicates that the rock undergoes both elastic and plastic deformation during this process, and the principal stress difference decreases with increasing axial strain. Therefore, it can be determined that the yield strength point is the boundary between the straight line and the curve in the stress-strain curve; the peak strength point is the point where the principal stress difference increases to its maximum value with increasing axial strain; and the residual strength point is the point where the principal stress difference decreases to its minimum value with increasing axial strain.

[0085] For example, the elastic modulus of rock can be calculated using the following formula:

[0086]

[0087] In the formula, E is the elastic modulus of the rock, with units of MPa; σ a ε is the principal stress difference at the yield strength point, in MPa; a Let be the axial strain at the yield strength point, which is dimensionless. The elastic modulus of the rock reflects the magnitude of the principal stress difference required to generate a unit axial strain.

[0088] For example, the principal stress difference at the yield strength point of the rock under predetermined test conditions can be read from the stress-strain curve as 45.9 MPa, and the axial strain as 2.50 × 10⁻⁶ MPa. -3 The principal stress difference at the peak strength point is 111.7 MPa, and the axial strain is 11.70 × 10⁻⁶ MPa. -3 The principal stress difference at the residual strength point is 82.3 MPa, and the axial strain is 22.80 × 10⁻⁶. -3 Therefore, the elastic modulus of the rock can be calculated using Formula 1, which is 18.36 × 10⁻⁶. 3 MPa is used to reflect the magnitude of the principal stress difference required to generate a unit axial strain.

[0089] S200, calculate the pre-peak brittleness index based on the stress-strain curve.

[0090] In this embodiment, the pre-peak brittleness index can be calculated by first calculating the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point based on the stress-strain curve; then calculating the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point based on the stress-strain curve; then calculating the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point based on the stress-strain curve; and finally calculating the pre-peak brittleness index based on the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, and the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point.

[0091] For example, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point is calculated by the following formula:

[0092]

[0093] In the formula, W ea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 ;σ a Where is the principal stress difference at the yield strength point, in MPa; E is the elastic modulus of the rock, in MPa. For example, by combining the principal stress difference at the yield strength point and the elastic modulus of the rock with Formula 2, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point is calculated to be 0.05738 × 10⁻⁶. 6 J / m 3 .

[0094] For example, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point is calculated by the following formula:

[0095]

[0096] In the formula, W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 ;σ b Here, represents the principal stress difference at the peak strength point, in MPa; and E represents the elastic modulus of the rock, in MPa. For example, by combining the principal stress difference at the peak strength point and the elastic modulus of the rock with Formula 3, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point is calculated to be 0.33978 × 10⁻⁶. 6 J / m 3 .

[0097] For example, the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point is calculated by the following formula:

[0098]

[0099] In the formula, W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 ;ε a ε is the axial strain at the yield strength point, dimensionless; b Let σ be the axial strain at the peak strength point, dimensionless; σ be the principal stress difference of the stress-strain curve, in MPa; and ε be the axial strain of the stress-strain curve, dimensionless. For example, by combining the axial strain at the yield strength point, the axial strain at the peak strength point, the principal stress difference of the stress-strain curve, and the axial strain using Formula 4, the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point is calculated to be 0.84967 × 10⁻⁶. 6 J / m 3 .

[0100] For example, the pre-peak brittleness index is calculated by the following formula:

[0101]

[0102] In the formula, B pre The pre-peak brittleness index is expressed as a percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 W ea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 For example, by combining the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, and the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point using Formula 5, the pre-peak brittleness index is calculated to be 33.2%.

[0103] S300. Calculate the post-peak brittleness index based on the stress-strain curve. In this embodiment, the post-peak brittleness index can be calculated by first calculating the energy sum based on the stress-strain curve, and then calculating the post-peak brittleness index based on the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, as well as the energy sum.

[0104] For example, energy is calculated using the following formula:

[0105]

[0106] In the formula, W g The sum of energy, in units of 10. 6 J / m 3 ;ε b ε represents the axial strain at the peak strength point, which is dimensionless. c σ is the axial strain at the residual strength point, dimensionless; σ is the principal stress difference of the stress-strain curve, in MPa; ε is the axial strain of the stress-strain curve, dimensionless; b Here, represents the principal stress difference at the peak strength point, in MPa; E represents the elastic modulus of the rock, in MPa. For example, by combining Equation 6 with the axial strain at the peak strength point, the axial strain at the residual strength point, the principal stress difference and axial strain of the stress-strain curve, and the elastic modulus of the rock, the calculated energy sum is 1.42526 × 10⁻⁶. 6 J / m 3 .

[0107] For example, the post-peak brittleness index is calculated using the following formula:

[0108]

[0109] In the formula, B post Post-peak brittleness index, in percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 W g The sum of energy, in units of 10. 6 J / m 3 For example, by combining the elastic strain energy and energy provided by the axial pressure difference per unit volume of rock at the peak strength point as described in Formula 7, the post-peak brittleness index is calculated to be 23.8%.

[0110] S400, the rock brittleness index is calculated based on the pre-peak brittleness index and the post-peak brittleness index.

[0111] In this embodiment of the disclosure, the rock brittleness index is calculated using the following formula:

[0112]

[0113] In the formula, B is the rock brittleness index, expressed as a percentage (%). pre B is the pre-peak brittleness index, expressed as a percentage. post This is the post-peak brittleness index, expressed as a percentage. For example, by combining the pre-peak and post-peak brittleness indices using Formula 8, the calculated rock brittleness index is 28.5%.

[0114] Based on the above method, this disclosure also provides a rock brittleness index calculation system 2000 corresponding to the above method, see [link to documentation]. Figure 3 , Figure 3 This embodiment of the present disclosure provides a structural block diagram of a rock brittleness index calculation system. The system includes a curve generation module 210, a pre-peak brittleness index module 220, a post-peak brittleness index module 230, and a rock brittleness index module 240. The curve generation module 210 is used to obtain a stress-strain curve by performing a triaxial compression test on the rock. The pre-peak brittleness index module 220 is used to calculate the pre-peak brittleness index based on the stress-strain curve. The post-peak brittleness index module 230 is used to calculate the post-peak brittleness index based on the stress-strain curve. The rock brittleness index module 240 is used to calculate the rock brittleness index based on the pre-peak and post-peak brittleness indices.

[0115] Based on the same inventive concept as the above-disclosed content, this disclosure also provides an electronic device 3000. For example... Figure 4 As shown, Figure 4 The present disclosure provides a block diagram of an electronic device. The electronic device 3000 of this embodiment includes at least one processor 310 and at least one memory 320 electrically connected to it. The memory 320 is electrically connected to the processor 310, and stores instructions executable by the at least one processor 310. The instructions are executed by the at least one processor 310 to enable the at least one processor 310 to perform the methods described above.

[0116] It should be noted that the electrical connection between the above-mentioned units does not necessarily mean the connection between lines. The indirect connection method can be applied to the embodiments of this disclosure as long as it achieves the purpose of this disclosure.

[0117] Based on the same inventive concept, this disclosure also provides a computer storage medium storing a computer program, which, when executed by a processor, is described as described above. The storage medium may include various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0118] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A method for calculating the brittleness index of rock, characterized in that, The method includes: Triaxial compression tests were conducted on rocks to obtain stress-strain curves. Calculate the pre-peak brittleness index based on the stress-strain curve; Calculate the post-peak brittleness index based on the stress-strain curve; The rock brittleness index is calculated based on the pre-peak brittleness index and the post-peak brittleness index.

2. The method according to claim 1, characterized in that, The triaxial compression test based on rock to obtain stress-strain curves includes: The triaxial compression test involves applying axial pressure to two sections of the rock; Obtain the stress-strain curve of the rock as the axial pressure gradually increases until the rock fractures.

3. The method according to claim 2, characterized in that, The triaxial compression test based on rock to obtain stress-strain curves includes: The stress-strain curve has the principal stress difference on the vertical axis and the axial strain on the horizontal axis.

4. The method according to claim 3, characterized in that, The triaxial compression test based on rock to obtain stress-strain curves includes: The stress-strain curve has the zero point, yield strength point, peak strength point, and residual strength point corresponding to the principal stress difference and axial strain.

5. The method according to claim 4, characterized in that, The stress-strain curve includes the zero point, yield strength point, peak strength point, and residual strength point corresponding to the principal stress difference and axial strain, including: The stress-strain curve is a straight line between the zero point and the yield strength point, and the principal stress difference increases with the increase of the axial strain.

6. The method according to claim 4, characterized in that, The stress-strain curve includes the zero point, yield strength point, peak strength point, and residual strength point corresponding to the principal stress difference and axial strain, including: The stress-strain curve is a curve between the yield strength point and the peak strength point, and the principal stress difference increases with the increase of the axial strain.

7. The method according to claim 4, characterized in that, The stress-strain curve includes the zero point, yield strength point, peak strength point, and residual strength point corresponding to the principal stress difference and axial strain, including: The stress-strain curve is a curve between the peak strength point and the residual strength point, and the principal stress difference decreases as the axial strain increases.

8. The method according to claim 4, characterized in that, The triaxial compression test based on rock to obtain stress-strain curves includes: The principal stress difference and axial strain of the yield strength point, peak strength point, and residual strength point are determined based on the shape of the stress-strain curve between two specific points.

9. The method according to claim 4, characterized in that, The triaxial compression test based on rock to obtain stress-strain curves includes: The elastic modulus of the rock is obtained based on the principal stress difference and axial strain at the yield strength point. The elastic modulus is calculated using the following formula: In the formula, E is the elastic modulus of the rock, with units of MPa; σ a ε is the principal stress difference at the yield strength point, in MPa; a The axial strain at the yield strength point is dimensionless.

10. The method according to claim 4, characterized in that, The calculation of the pre-peak brittleness index based on the stress-strain curve includes: The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point is calculated based on the stress-strain curve. The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point is calculated by the following formula: In the formula, W ea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 ;σ a ρ represents the principal stress difference at the yield strength point, in MPa; E represents the elastic modulus of the rock, in MPa.

11. The method according to claim 10, characterized in that, The calculation of the pre-peak brittleness index based on the stress-strain curve includes: The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point is calculated based on the stress-strain curve. The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point is calculated by the following formula: In the formula, W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 ;σ b denoted as the principal stress difference at the peak strength point, in MPa; E is the elastic modulus of the rock, in MPa.

12. The method according to claim 11, characterized in that, The calculation of the pre-peak brittleness index based on the stress-strain curve includes: Calculate the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point based on the stress-strain curve; The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point is calculated by the following formula: In the formula, W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 ;ε a ε is the axial strain at the yield strength point, dimensionless; b σ is the axial strain at the peak strength point, dimensionless; σ is the principal stress difference of the stress-strain curve, in MPa; ε is the axial strain of the stress-strain curve, dimensionless.

13. The method according to claim 12, characterized in that, The calculation of the pre-peak brittleness index based on the stress-strain curve includes: The pre-peak brittleness index is calculated based on the elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, the elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, and the energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point.

14. The method according to claim 13, characterized in that, The pre-peak brittleness index, calculated based on the stress-strain curve, is determined by the following formula: In the formula, B pre The pre-peak brittleness index is expressed as a percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 ; W ea The elastic strain energy provided by the axial pressure difference per unit volume of rock at the yield strength point, in units of 10. 6 J / m 3 ; W d The energy provided by the axial pressure difference per unit volume of rock from the yield strength point to the peak strength point, expressed in units of 10. 6 J / m 3 .

15. The method according to claim 14, characterized in that, The calculation of the post-peak brittleness index based on the stress-strain curve includes: Calculate the energy based on the stress-strain curve; The energy is calculated using the following formula: In the formula, W g The sum of energy, in units of 10. 6 J / m 3 ;ε b ε represents the axial strain at the peak strength point, which is dimensionless. c σ is the axial strain at the residual strength point, dimensionless; σ is the principal stress difference of the stress-strain curve, in MPa; ε is the axial strain of the stress-strain curve, dimensionless; b denoted as the principal stress difference at the peak strength point, in MPa; E is the elastic modulus of the rock, in MPa.

16. The method according to claim 15, characterized in that, The calculation of the post-peak brittleness index based on the stress-strain curve includes: The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, as well as the energy and the post-peak brittleness index, are calculated.

17. The method according to claim 16, characterized in that, The elastic strain energy provided by the axial pressure difference per unit volume of rock based on the peak strength point, as well as the energy and post-peak brittleness index, are calculated using the following formula: In the formula, B post Post-peak brittleness index, in percentage (%); W eb The elastic strain energy provided by the axial pressure difference per unit volume of rock at the peak strength point, in units of 10. 6 J / m 3 ; W g The sum of energy, in units of 10. 6 J / m 3 .

18. The method according to claim 17, characterized in that, The calculation of the rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index includes: The rock brittleness index is calculated using the following formula: In the formula, B is the rock brittleness index, expressed as a percentage (%). pre B is the pre-peak brittleness index, expressed as a percentage. post Post-peak fragility index, expressed as a percentage.

19. A rock brittleness index calculation system, characterized in that, The system includes: The curve generation module is used to perform a triaxial compression test on the rock after obtaining it in order to obtain a stress-strain curve. The pre-peak brittleness index module is used to calculate the pre-peak brittleness index based on the stress-strain curve. The post-peak brittleness index module is used to calculate the post-peak brittleness index based on the stress-strain curve. The rock brittleness index module is used to calculate the rock brittleness index based on the pre-peak brittleness index and the post-peak brittleness index.

20. An electronic device, characterized in that, The electronic device includes: Memory, used to store computer programs; A processor, configured to implement a rock brittleness index calculation method as described in any one of claims 1 to 18 when executing the computer program.

21. A computer storage medium storing a computer program, wherein the computer program, when executed by a processor, implements a method for calculating a rock brittleness index as described in any one of claims 1 to 18.

Images