Shale bedding mechanical property inversion method, equipment and medium

Abstract

The invention relates to the technical field of rock mass mechanical analysis, and discloses a shale bedding mechanical property inversion method, equipment and a medium. The method comprises the following steps: acquiring a mechanical signal and a generated electric signal when a target shale is fractured under external applied force; dividing the shale fracture process into a plurality of time intervals according to a plurality of characteristic events in the electric signals and a bedding geometric model of the shale, and enabling each time interval to correspond to an expansion stage of a shale crack in one bedding interval; according to the equivalent path length of the crack in each bedding interval and the time difference between the adjacent characteristic events, determining the expansion speed of the crack in each bedding interval; according to the mechanical signals and a bedding geometric model, determining the stress intensity of each bedding interval of the shale in the fracture process; according to the stress intensity and the expansion speed, the equivalent fracture energy and fracture toughness of each bedding section of the shale in the fracture process are determined through the energy balance relation of the bedding sections in the fracture process, and therefore the shale bedding mechanical properties are inverted.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics analysis technology, and in particular to a method, equipment and medium for inverting the mechanical properties of shale bedding. Background Technology

[0002] In unconventional oil and gas development, deep rock engineering, and underground reservoir construction, the mechanical properties of shale-like layered rock masses directly affect engineering safety and reservoir stimulation effectiveness, serving as core elements in engineering design and reservoir evaluation. Shale is characterized by widespread bedding planes and weak interlayers, making it a typical highly anisotropic rock mass. Key parameters such as its elastic modulus, tensile strength, and fracture toughness vary significantly with bedding angles. Furthermore, the failure modes and crack propagation paths of shale differ markedly at different bedding angles. Bedding planes often become the initiation point and dominant propagation path of cracks, exacerbating the complexity of the rock mass's mechanical response.

[0003] Currently, the methods for obtaining the mechanical properties of shale bedding typically include: (1) preparing multiple sets of samples at different bedding angles and measuring the overall mechanical parameters through tests such as three-point bending, Brazilian splitting, and uniaxial / triaxial compression; (2) tracking the crack propagation path and crack tip location by combining digital image correlation (DIC), acoustic emission (AE), or high-speed photography, and then obtaining the parameters using fracture mechanics models or finite element inversion; (3) empirically fitting the bedding-controlled failure based on load-displacement curves, peak strength, or failure morphology.

[0004] However, for strongly anisotropic shale, cracks tend to deflect, bifurcate, or intermittently jump along bedding planes. The methods mentioned above only obtain the mechanical parameters of the shale as a whole, making it difficult to segment and identify the cracks according to bedding planes during a single fracture process. They also fail to reflect the differences in mechanical properties when cracks propagate in different bedding planes. Summary of the Invention

[0005] The purpose of this invention is to provide a method, equipment, and medium for inverting the mechanical properties of shale bedding, which can solve the problem of not being able to obtain the mechanical properties when different bedding intervals of shale are extended.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for inverting the mechanical properties of shale bedding, comprising the following steps: Based on the geometric dimensions and bedding spacing of the target shale, a bedding geometric model is established; Acquire the mechanical signals and electrical signals generated when the target shale fractures under external force; By identifying peaks, peak clusters, and silent regions in the electrical signal, multiple characteristic events of the electrical signal are determined. Based on these multiple characteristic events and the bedding geometry model, the fracture process of the target shale is divided into multiple time intervals. Each time interval corresponds to the propagation stage of the crack in the target shale within a bedding interval. The equivalent path length of the crack in each bedding interval is determined based on the bedding geometry model, and the average propagation rate of the crack in each bedding interval is determined based on the equivalent path length and the time difference between adjacent characteristic events. Based on mechanical signals and bedding geometry models, the stress intensity factor of each bedding interval of the target shale during the fracture process is determined; Based on the stress intensity factor and average propagation rate, the equivalent fracture energy and fracture toughness of each bedding interval of the target shale during the fracture process are determined by the energy balance relationship of the bedding intervals during the fracture process.

[0007] Furthermore, the equivalent fracture energy of each bedding interval of the target shale during the fracture process is determined using the following formula: ; ; ; In the formula, The equivalent fracture energy of the current bedding interval of the target shale during the fracture process. This represents the average crack propagation rate within the current bedding interval. Let be the Poisson's ratio of the target shale, and 'a' be a preset correction factor. This corresponds to the equivalent path length. The time difference between adjacent feature events. For Ruilibo speed, For longitudinal wave velocity, Stress intensity factor It is the equivalent elastic modulus.

[0008] Furthermore, the fracture toughness of each bedding interval of the target shale during the fracture process is determined using the following formula: ; In the formula, This represents the fracture toughness of the target shale in the corresponding bedding interval when the crack velocity approaches 0.

[0009] Furthermore, the mechanical signal and the electrical signal are obtained through the following means: The loading unit applies a predetermined load to a target shale with pre-existing cracks to cause the target shale to fracture along the crack propagation path indicated by the pre-existing cracks. A current application unit electrically connected to the target shale is used to apply current into the interior of the target shale; An electrical signal acquisition unit electrically connected to the target shale is used to acquire electrical signals generated during the crack propagation process of the target shale; A mechanical data acquisition unit electrically connected to the target shale is used to acquire mechanical signals of the target shale during the loading process.

[0010] Furthermore, the loading unit is a three-point bending loading system, including: an upper loading head, a first support roller and a second support roller, the target shale spanning between the first support roller and the second support roller, the upper loading head being located at the midpoint of the target shale span, and an insulating mica sheet being provided at the contact position between the target shale and the first support roller and the second support roller.

[0011] Furthermore, a first injection electrode and a second injection electrode are arranged at both ends of the target shale along its length, away from the location of the pre-fabricated crack. The current application unit is electrically connected to the first injection electrode and the second injection electrode via a wire to apply current into the interior of the target shale.

[0012] Furthermore, a first acquisition electrode and a second acquisition electrode are arranged near the tip of the pre-formed crack on both ends of the target shale in the width direction. The electrical signal acquisition unit is electrically connected to the first acquisition electrode and the second acquisition electrode through a wire to acquire the electrical signal generated during the crack propagation process of the target shale.

[0013] Furthermore, the mechanical signals include load, displacement or stress, and strain signals of the target shale, and the electrical signals include potential changes, resistivity changes, or charge pulse signals generated by the target shale.

[0014] Embodiments of the present invention also provide a computer device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described shale bedding mechanical property inversion method.

[0015] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for inverting the mechanical properties of shale bedding.

[0016] The method for inverting the mechanical properties of shale bedding provided by this invention has at least the following beneficial effects: Because crack propagation in shale reconstructs the conductive pathways of the rock mass and alters the potential distribution, the electrical signals exhibit stage characteristics such as peak values, peak clusters, and silent zones. Furthermore, bedding angles modulate the temporal and amplitude characteristics of the electrical signals. Therefore, the crack evolution law controlled by bedding can be inferred from the electrical signals generated during shale fracture, thereby obtaining the mechanical properties of shale bedding. This invention combines the mechanical signals of shale fracture under external force with the corresponding generated electrical signals to invert the mechanical properties of shale bedding. The stage characteristics of the aforementioned electrical signals, such as peak values, peak clusters, and silent zones, are used as characteristic events to divide the electrical signals. Each time interval corresponds to the propagation stage of the crack in the target shale fracture within a bedding interval, thus obtaining the fracture electrical signals for different bedding intervals. Then, the crack propagation velocity of each bedding interval is inverted using the time structure of the electrical signals. Finally, the stress intensity factor of each bedding interval during the fracture process is obtained by combining the bedding geometric model and the mechanical signals (fracture mechanics model) to determine the equivalent fracture energy and fracture toughness (mechanical properties) of each bedding interval during the fracture process.

[0017] As can be seen, this invention realizes the mapping of bedding intervals in the crack propagation process, and can invert the equivalent fracture energy and fracture toughness of different bedding intervals, achieving fine layer identification. It is applicable to the inversion of mechanical properties of complex failure scenarios such as crack deflection and intermittent propagation under the control of shale bedding, and does not require external visualization methods such as high-speed photography / DIC, thus improving feasibility. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A flowchart illustrating a method for inverting the mechanical properties of shale bedding provided by this invention; Figure 2 A schematic diagram of a shale bedding mechanical property inversion device provided by the present invention. Figure 1 ; Figure 3 A schematic diagram of a shale bedding mechanical property inversion device provided by the present invention. Figure 2 ; Figure 4 A schematic diagram of a shale bedding mechanical property inversion device provided by the present invention. Figure 3 . Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Existing methods for measuring crack propagation in rock masses are mainly divided into three categories: high-speed photography for direct observation, strain gauge / dedicated crack propagation meter for electrical signal testing, and compliance / potential method for indirect calculation. All of these methods have significant limitations and are difficult to adapt to the testing needs of bedding shale. While high-speed photography can visually present crack morphology, it requires high-resolution equipment and a professional analysis system, resulting in high costs and stringent requirements for the experimental environment. Rock debris generated by shale loading can easily interfere with identification, and it cannot accurately capture the initial micro-cracks on the bedding planes, leading to high computational costs for subsequent data processing. Strain gauges and traditional crack propagation methods are stable in homogeneous materials, but when applied to heterogeneous bedding shale, the difficulty in predicting crack paths leads to random placement of sensing elements, and the high ductility of the resistance wire causes signal response lag. Bedding slip can also easily cause element peeling, making it difficult to monitor cracks in multiple regions. The compliance method and potential method rely on standard samples and pre-calibrated curves. When facing non-standard shale samples with strong bedding heterogeneity, calibration is difficult, calculation errors are high, and only macroscopic crack information can be obtained, failing to achieve layered identification of mechanical parameters in bedding intervals.

[0022] In recent years, electrical signals induced by rock fracture, such as resistivity, potential, charge, and electromagnetic radiation, have been increasingly used in crack monitoring experiments. Studies have confirmed that crack propagation reconstructs the conductive pathways of rock masses and alters the potential distribution, causing electrical signals to exhibit stage characteristics such as peaks, peak clusters, and silent zones. Bedding angles also modulate the temporal and amplitude characteristics of electrical signals, theoretically allowing for the inverse deduction of bedding-controlled crack evolution patterns. However, current technologies only utilize these electrical signals for damage monitoring, crack location, or disaster early warning, merely outputting crack activity intensity or instability risk. They have neither established a quantitative correlation between electrical signals and crack propagation speed nor used them as core inputs for inverting rock mass mechanical parameters. Furthermore, they lack a dedicated technical system for inverting the mechanical properties of layered fractures using electrical signals in bedding shale.

[0023] Therefore, developing a technical solution that relies on shale fracture electrical signals and crack propagation velocity to invert key parameters such as equivalent fracture energy and fracture toughness in each bedding interval has significant theoretical innovation and engineering practical value for overcoming the limitations of traditional methods and achieving accurate identification of the stratified mechanical properties of highly anisotropic shale. This invention relies on shale fracture electrical signals and crack propagation velocity to invert key mechanical property parameters such as equivalent fracture energy and fracture toughness in each bedding interval, thereby achieving accurate identification of the stratified mechanical properties of highly anisotropic shale.

[0024] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] One embodiment of the present invention relates to a method for inverting the mechanical properties of shale bedding. The specific process of the method for inverting the mechanical properties of shale bedding in this embodiment can be as follows: Figure 1 As shown, it includes: Step 101: Establish a bedding geometric model based on the geometric dimensions and bedding spacing of the target shale.

[0026] Step 102: Obtain the mechanical signals and electrical signals generated when the target shale fractures under external force.

[0027] Step 103: By identifying peaks, peak clusters, and silent regions in the electrical signal, multiple characteristic events of the electrical signal are determined. Based on the multiple characteristic events and the bedding geometry model, the fracture process of the target shale is divided into multiple time intervals. Each time interval corresponds to the propagation stage of the crack in the target shale within a bedding interval.

[0028] Step 104: Determine the equivalent path length of the crack in each bedding interval based on the bedding geometry model, and determine the average propagation rate of the crack in each bedding interval based on the equivalent path length and the time difference between adjacent characteristic events.

[0029] Step 105: Based on the mechanical signals and the bedding geometry model, determine the stress intensity factor of each bedding interval of the target shale during the fracture process.

[0030] Step 106: Based on the stress intensity factor and average propagation rate, determine the equivalent fracture energy and fracture toughness of each bedding interval of the target shale during the fracture process through the energy balance relationship of the bedding intervals during the fracture process.

[0031] The following is a detailed description of the implementation details of the shale bedding mechanical property inversion method in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0032] This embodiment acquires electrical and mechanical signals simultaneously during a single loading test, uses the time structure of the electrical signals to invert the segmented crack propagation velocity, and then combines it with a fracture mechanics model to obtain the equivalent mechanical properties of each bedding interval.

[0033] Step 1, Sample preparation and parameter setting: Obtain shale cores with obvious bedding structures (i.e., target shale) as shale samples. First, cut them into standard samples according to the predetermined bedding angle, such as 0° bedding semicircular three-point bending samples, rectangular samples with pre-fabricated cracks, etc. Measure the geometric dimensions and bedding spacing of the samples, establish a bedding geometric model and input it into the data processing system.

[0034] Step 2, Electrode arrangement and loading configuration: Several electrodes or charge sensors are arranged on the surface of the specimen along the expected crack propagation path. The electrodes are connected to the electrical signal acquisition circuit through wires. The specimen is installed in the loading fixture of a servo universal testing machine or a split Hopkinson bar device, and the loading rate, loading direction and maximum load are set.

[0035] The third step is to collect data synchronously. During the loading process, the mechanical data acquisition unit is used to collect loading force, displacement or stress, strain signals (mechanical signals) in real time; the electrical signal acquisition unit is used to collect potential changes, resistivity changes or charge pulse signals generated during the fracture process (electrical signals) at a high sampling frequency, and the two types of signals are recorded synchronously through a unified time reference.

[0036] Step 4: Electrical signal feature extraction and time segmentation: The acquired electrical signals are denoised, filtered, and smoothed. Threshold criteria and time window criteria are used to identify peaks, peak clusters, and silent regions in the electrical signals to obtain a set of characteristic event time points. Based on the characteristic events and bedding geometry information, the entire fracture process is divided into multiple time intervals, each time interval corresponding to the crack propagation stage within a certain bedding interval or bedding group.

[0037] Step 5: Calculation of segmented crack propagation rate: Within each time interval, the equivalent path length of the crack is determined based on the layering geometry model. And calculate the time difference between adjacent feature events. According to the formula The average crack propagation rate in this region is obtained. This establishes the relationship between the velocity and time of segmented cracks.

[0038] Step 6, Fracture mechanics parameter inversion: Based on the specimen geometry and applied load, the stress intensity factor for each interval is determined using the standard geometric correction function or the finite element method. Within the framework of dynamic fracture mechanics, the energy balance equation is adopted. Calculate the crack in the first... i Equivalent fracture energy of the interval This is considered as the fracture property parameter of the bedding interval; if necessary, the equivalent fracture strength and critical cracking displacement of each bedding interval can be further inverted by combining the condensation zone model.

[0039] In this embodiment, electrodes or charge sensors are first deployed at predetermined positions on the surface of the shale sample. Under controlled loading conditions, loading mechanical signals and fracture electrical signals are simultaneously acquired. After electrical signal filtering and feature recognition, peak values, peak clusters, and silent regions are extracted, and fracture time intervals are divided. The crack propagation rate of each interval is calculated by combining the bedding geometry and the time difference between adjacent characteristic events. Then, based on the dynamic fracture mechanics relationship, the segmented propagation rate is coupled with the stress intensity factor and energy release rate to invert the fracture energy, fracture toughness, and other mechanical parameters of each bedding interval. Compared with existing electrical signal technology that is only used for damage monitoring and early warning, this invention can achieve layered quantitative identification of the mechanical properties of shale bedding through a single test, improving testing efficiency and parameter accuracy. It is suitable for evaluation of unconventional oil and gas reservoirs and engineering analysis of layered rock masses.

[0040] In some embodiments, to implement the above-described method for inverting the mechanical properties of shale bedding, the present invention provides a device for inverting the mechanical properties of shale bedding, comprising: The loading unit applies a predetermined load to a target shale with pre-existing cracks to cause the target shale to fracture along the crack propagation path indicated by the pre-existing cracks; wherein the loading method may include static loading or dynamic loading. The sample clamping and electrode arrangement unit is used to fix the target shale and arrange electrodes or charge sensors on its surface; A current application unit electrically connected to the target shale (via an electrode or charge sensor) is used to apply current into the interior of the target shale; An electrical signal acquisition unit electrically connected to the target shale is used to acquire electrical signals generated during the crack propagation process of the target shale; A mechanical data acquisition unit electrically connected to the loading unit and the target shale is used to acquire mechanical signals of the target shale during the loading process; The data synchronization and storage unit is used to synchronize and store electrical and mechanical signals in time.

[0041] Figures 2 to 4 The specific device structure is given, which mainly consists of a loading unit (i.e., a three-point bending loading system) 1, a shale sample 2, an electrical signal acquisition unit 3, a pre-formed crack 4, a mechanical signal acquisition unit 5, a current application unit 6, a wire 7, an upper loading head 11, an insulating mica sheet 12, a first support roller 13, a second support roller 14, a first acquisition electrode 31, a second acquisition electrode 32, a crack propagation path 41, a first injection electrode 61, and a second injection electrode 62. The shale sample 2 is mounted on the three-point bending loading system 1. The current application unit 6 is connected to the shale sample 2 to apply current inside the shale sample. The electrical signal acquisition unit 3 is electrically connected to the acquisition electrode on the surface of the shale sample 2 to acquire electrical signals generated during crack propagation. The mechanical signal acquisition unit 5 is connected to the three-point bending loading system 1 to acquire mechanical signals during the loading process.

[0042] When shale sample 2 fractures due to the force applied by the three-point bending loading system 1, the crack in the shale body will fracture along the crack propagation path 41 due to the presence of pre-existing crack 4. Since the inherent properties of the shale body determine that it will generate a small electrical signal when fracture occurs, the current application unit 6 is used to integrate the system into an energized circuit. Then, the changes in the electrical signal are collected by the electrical signal acquisition unit 3, and the change law of the electrical signal is summarized. Finally, the law is combined with the mechanical signal acquisition unit 5 to obtain the fracture velocity of different layers of the shale body. Then, the specific mechanical properties of the shale body are calculated by combining the fracture mechanics formula.

[0043] The three-point bending loading system 1 includes an upper loading head 11, a first support roller 13, and a second support roller 14. The shale sample 2 is straddling the first support roller 13 and the second support roller 14, with the upper loading head 11 located at the midpoint of the sample. A pre-fabricated crack 4 is provided on the lower surface of the middle part of the shale sample 2 to control the crack initiation position, so that the crack starts from the pre-fabricated crack 4 during loading and extends along the thickness direction of the sample, forming a crack propagation path 41. An insulating mica sheet 12 is provided at the contact position between the shale sample 2 and the support roller to isolate the electrical contact between the loading system and the sample, and to avoid interference from the loading device to the electrical signal measurement.

[0044] The current application unit 6 is electrically connected to the first injection electrode 61 and the second injection electrode 62 via wires 7. The first injection electrode 61 and the second injection electrode 62 are respectively arranged at both ends of the shale sample 2 along its length, away from the location of the pre-crack 4, to apply current inside the shale mass, thereby forming a stable conductive path inside the sample. During loading, the current application device 6 continuously applies current to the sample, ensuring that crack propagation always occurs within the applied current field.

[0045] The electrical signal acquisition unit 3 is electrically connected to the first acquisition electrode 31 and the second acquisition electrode 32 via wires 7. The first acquisition electrode 31 and the second acquisition electrode 32 are located near the tip of the pre-fabricated crack 4, arranged at both ends of the shale body sample 2 in the width direction. When the crack is initiated and propagated by the pre-fabricated crack 4 under three-point bending loading conditions, the crack will disrupt the conductive path inside the shale body, causing changes in the electrical signals between the acquisition electrodes. The electrical signal acquisition unit 3 records these changes in real time. In other embodiments, the acquisition electrodes can be arranged into multiple acquisition units along the crack propagation direction to acquire the electrical signals generated during the propagation of the crack in different bedding intervals.

[0046] Mechanical signal acquisition and synchronous acquisition: The mechanical signal acquisition device 5 is connected to the three-point bending loading system 1 and is used to acquire the load, displacement or stress and strain signals of the specimen during the loading process.

[0047] The electrical signal acquisition device 3 and the mechanical signal acquisition device 5 are synchronously acquired using a unified time reference, so that the electrical signals generated during crack propagation correspond one-to-one with the mechanical loading signals in time.

[0048] During the experiment, the shale sample 2 was continuously loaded by the three-point bending loading system 1, and the current application device 6 applied current to the inside of the sample. The electrical signal acquisition unit 3 and the mechanical signal acquisition unit 5 synchronously recorded the electrical and mechanical signals during the crack propagation process.

[0049] During crack propagation, electrical signals exhibit characteristics such as peaks, peak clusters, or silent regions. The time interval between adjacent electrical signal peaks corresponds to the crack propagation process within a certain bedding interval. Let the crack propagate at the [missing information - likely a specific point in time]. i The equivalent extension length within each stratification interval is: The time interval between adjacent characteristic electrical signals is The average crack propagation rate within this interval is , can be represented as: .

[0050] By combining the specimen's geometric parameters and loading conditions, the stress intensity factor and fracture energy of the crack in each interval can be further calculated, thereby inverting the equivalent mechanical properties of different bedding intervals. The specific derivation process is as follows: Static energy release rate of Mode I crack under linear elastic conditions With stress intensity factor satisfy: ,in It is the equivalent elastic modulus.

[0051] When the crack moves at a speed When dynamically expanding, a dimensionless velocity correction function needs to be introduced. ,in For Rayleigh wave velocity, the dynamic energy release rate is: When the crack propagates stably, we have: The dynamic velocity correction function is: ; For longitudinal wave velocity, ; represents the transverse wave velocity. ; Let be the material density. Substituting the calculated average propagation rate into the formula yields the velocity-dependent fracture energy. Substituting the values ​​of different strata into the formula yields the velocity-dependent fracture energy for each stratification layer. The formula is as follows: .

[0052] After obtaining the velocity-dependent fracture energy function, because when the crack velocity approaches 0, If the value approaches 1, meaning it has no effect on the magnitude of the fracture energy, then: The static fracture toughness can be obtained by calculating the limit of this function. .

[0053] The above fracture mechanics equations are merely one example of an implementation of the present invention. Those skilled in the art can achieve the same technical effects using other equivalent fracture mechanics models or energy relationships without departing from the technical concept of the present invention. In summary, this invention provides a method and apparatus for inverting the mechanical properties of shale bedding based on fracture electrical signals and crack propagation rates. By simultaneously acquiring electrical and mechanical signals in a single loading test, the segmented crack propagation rates are inverted using the time structure of the electrical signals, and then the equivalent mechanical properties of each bedding interval are obtained by combining them with a fracture mechanics model.

[0054] Compared with the prior art, the present invention has the following advantages: (1) This invention combines the time structure of electrical signals during shale fracture with the segmented propagation behavior of cracks in bedding rock mass, and realizes the quantitative calculation of crack propagation rate in each bedding interval by inferring from electrical signals.

[0055] (2) Under the framework of dynamic fracture mechanics, this invention combines the segmented crack propagation rate with the stress intensity factor and energy release rate, and proposes an inversion method for layered equivalent fracture energy and fracture toughness, which can quantitatively identify the differences in mechanical properties of shale bedding.

[0056] (3) The test device and data processing system provided by the present invention can simultaneously obtain fracture electrical signals and delamination mechanical parameters in a single loading test, which reduces the number of samples compared with traditional methods and makes fuller use of information.

[0057] (4) The “electrical signal-crack velocity-mechanical property” inversion technology proposed in this invention can be extended to other rock masses with layered or jointed structures, providing new parameter acquisition methods for the evaluation and engineering design of unconventional oil and gas reservoirs.

[0058] Another embodiment of the present invention relates to a computer device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the shale bedding mechanical property inversion method of the above embodiments.

[0059] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0060] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0061] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method embodiments described above.

[0062] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of the present 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.

[0063] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for inverting the mechanical properties of shale bedding, characterized in that, The method includes: Based on the geometric dimensions and bedding spacing of the target shale, a bedding geometric model is established; Acquire the mechanical signals and electrical signals generated when the target shale fractures under external force; By identifying peaks, peak clusters, and silent regions in the electrical signal, multiple characteristic events of the electrical signal are determined. Based on these multiple characteristic events and the bedding geometry model, the fracture process of the target shale is divided into multiple time intervals. Each time interval corresponds to the propagation stage of the crack in the target shale within a bedding interval. The equivalent path length of the crack in each bedding interval is determined based on the bedding geometry model, and the average propagation rate of the crack in each bedding interval is determined based on the equivalent path length and the time difference between adjacent characteristic events. Based on mechanical signals and bedding geometry models, the stress intensity factor of each bedding interval of the target shale during the fracture process is determined; Based on the stress intensity factor and average propagation rate, the equivalent fracture energy and fracture toughness of each bedding interval of the target shale during the fracture process are determined by the energy balance relationship of the bedding intervals during the fracture process.

2. The method for inverting the mechanical properties of shale bedding according to claim 1, characterized in that, The equivalent fracture energy of each bedding interval of the target shale during the fracture process can be determined using the following formula: ； ； ； In the formula, Let v be the equivalent fracture energy of the current bedding interval of the target shale during the fracture process, and v be the average crack propagation rate of the current bedding interval. Let be the Poisson's ratio of the target shale, and 'a' be a preset correction factor. This corresponds to the equivalent path length. The time difference between adjacent feature events. For Ruilibo speed, For longitudinal wave velocity, It is a type I stress intensity factor. It is the equivalent elastic modulus.

3. The method for inverting the mechanical properties of shale bedding according to claim 2, characterized in that, The fracture toughness of each bedding interval of the target shale during the fracture process is determined using the following formula: ； In the formula, This represents the fracture toughness of the target shale in the corresponding bedding interval when the crack velocity approaches 0.

4. The method for inverting the mechanical properties of shale bedding according to claim 1, characterized in that, The mechanical signal and the electrical signal are obtained through the following means: The loading unit applies a predetermined load to a target shale with pre-existing cracks to cause the target shale to fracture along the crack propagation path indicated by the pre-existing cracks. A current application unit electrically connected to the target shale is used to apply current into the interior of the target shale; An electrical signal acquisition unit electrically connected to the target shale is used to acquire electrical signals generated during the crack propagation process of the target shale; A mechanical data acquisition unit electrically connected to the target shale is used to acquire mechanical signals of the target shale during the loading process.

5. The method for inverting the mechanical properties of shale bedding according to claim 4, characterized in that, The loading unit is a three-point bending loading system, including: an upper loading head, a first support roller and a second support roller. The target shale is spanned between the first support roller and the second support roller. The upper loading head is located at the middle of the target shale span, and an insulating mica sheet is provided at the contact position between the target shale and the first support roller and the second support roller.

6. The method for inverting the mechanical properties of shale bedding according to claim 5, characterized in that, The target shale has a first injection electrode and a second injection electrode arranged at both ends of the target shale along its length, away from the location of the pre-fabricated crack. The current application unit is electrically connected to the first injection electrode and the second injection electrode through a wire to apply current into the target shale.

7. The method for inverting the mechanical properties of shale bedding according to claim 6, characterized in that, The target shale is equipped with a first and a second acquisition electrode located near the tip of the pre-formed crack at both ends of the target shale width direction. The electrical signal acquisition unit is electrically connected to the first and the second acquisition electrodes via wires to acquire the electrical signals generated during the crack propagation process of the target shale.

8. The method for inverting the mechanical properties of shale bedding according to any one of claims 1 to 7, characterized in that, The mechanical signals include load, displacement or stress, and strain signals of the target shale, and the electrical signals include potential changes, resistivity changes, or charge pulse signals generated by the target shale.

9. A computer device, characterized in that, include: At least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the shale bedding mechanical property inversion method as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the shale bedding mechanical property inversion method as described in any one of claims 1 to 8.

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