CN-122016459-A - Shale layer physical and mechanical property inversion method, equipment and medium

CN122016459ACN 122016459 ACN122016459 ACN 122016459ACN-122016459-A

Abstract

The invention relates to the technical field of rock mass mechanics analysis, and discloses a shale layer physical and mechanical property inversion method, equipment and medium. The method comprises the steps of obtaining a mechanical signal and a generated electric signal when a target shale breaks under external applied force, dividing a shale breaking process into a plurality of time intervals according to a plurality of characteristic events in the electric signal and a layer geometrical model of the shale, wherein each time interval corresponds to an expansion stage of the shale crack in one layer interval, determining the expansion speed of the crack in each layer interval according to the equivalent path length of the crack in each layer interval and the time difference between adjacent characteristic events, determining the stress intensity of each layer interval of the shale in the breaking process according to the mechanical signal and the layer geometrical model, and determining the equivalent breaking energy and the breaking toughness of each layer interval of the shale in the breaking process according to the stress intensity and the expansion speed and the energy balance relation of the layer interval in the breaking process, so that the mechanical property of the shale layer is inverted.

Inventors

LUO NING
MA GUANGRUI
CHAI YABO
ZHANG HU
ZHOU JIANAN
LIANG GUOFENG

Assignees

中国矿业大学

Dates

Publication Date: 20260512
Application Date: 20260202

Claims (10)

1. A shale layer physical and mechanical property inversion method, the method comprising: Establishing a bedding geometrical model according to the geometrical size and bedding interval of the target shale; Acquiring a mechanical signal and a generated electric signal when the target shale is broken under external applied force; determining a plurality of characteristic events of the electric signal by identifying peaks, peak clusters and silence areas in the electric signal, dividing the fracture process of the target shale into a plurality of time intervals according to the plurality of characteristic events and the layer-by-layer geometric model, wherein each time interval corresponds to the expansion stage of the fracture crack of the target shale in one layer-by-layer interval; determining the equivalent path length of each layer interval crack according to the layer geometrical model, and determining the average expansion speed of each layer interval crack according to the equivalent path length and the time difference between adjacent characteristic events; According to the mechanical signals and the bedding geometrical model, determining stress intensity factors of each bedding interval of the target shale in the fracture process; And determining the equivalent fracture energy and fracture toughness of each interval of the target shale in the fracture process according to the stress intensity factor and the average expansion speed and through the energy balance relation of the intervals in the fracture process.
2. The shale layer physical mechanics inversion method of claim 1 wherein the equivalent fracture energy of each interval of the target shale layer during fracture is determined by the following formula: ; ; ; In the formula, For the equivalent fracture energy of the target shale in the fracture process of the current interval, v is the average expansion speed of the cracks of the current interval, For the poisson ratio of the target shale, a is a preset correction coefficient, In order to correspond to the equivalent path length, For the time difference between adjacent feature events, For the wave velocity of the rayleigh wave, In order to achieve the wave velocity of the longitudinal wave, Is a stress intensity factor of the type I, Is the equivalent elastic modulus.
3. The shale layer physical mechanical properties inversion method of claim 2, wherein the fracture toughness of each interval of the target shale layer during fracture is determined by the following formula: ; In the formula, Fracture toughness of the target shale corresponding to the interval of the layer is set at a crack velocity approaching 0.
4. The inversion method of the mechanical properties of shale layers according to claim 1, wherein the mechanical signals and the electrical signals are obtained by: a loading unit for applying a predetermined load to the target shale provided with the pre-cracks so as to fracture the target shale along a crack propagation path indicated by the pre-cracks; a current applying unit electrically connected with the target shale for applying a current to the inside of the target shale; The electric signal acquisition unit is electrically connected with the target shale and is used for acquiring electric signals generated in the process of crack propagation of the target shale; And the mechanical data acquisition unit is electrically connected with the target shale and is used for acquiring mechanical signals of the target shale in the loading process.
5. The inversion method of the mechanical properties of the shale layer according to claim 4, wherein the loading unit is a three-point bending loading system and comprises an upper loading head, a first supporting roller and a second supporting roller, the target shale is arranged between the first supporting roller and the second supporting roller in a straddling mode, the upper loading head is positioned at a straddling position of the target shale, and an insulating mica sheet is arranged at a contact position of the target shale and the first supporting roller and the second supporting roller.
6. The inversion method of the mechanical properties of the shale layer according to claim 5, wherein the first injection electrode and the second injection electrode far from the position where the pre-crack is located are arranged on the two end areas of the target shale in the length direction, and the current applying unit is electrically connected with the first injection electrode and the second injection electrode through wires so as to apply current to the inside of the target shale.
7. The inversion method of the mechanical properties of the shale layer according to claim 6, wherein a first collecting electrode and a second collecting electrode close to the tip of the pre-crack are arranged on two end areas of the width direction of the target shale, and the electric signal collecting unit is electrically connected with the first collecting electrode and the second collecting electrode through wires so as to collect electric signals generated in the process of expanding the target shale crack.
8. The inversion method of the mechanical properties of the shale layer according to any of claims 1 to 7, wherein the mechanical signals comprise load, displacement or stress, strain signals of the target shale, and the electrical signals comprise potential changes, resistivity changes or charge pulse signals generated by the target shale.
9. A computer device comprising at least one processor and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the shale layer mechanical properties inversion method of any of claims 1-8.
10. A computer readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the shale layer physical mechanics property inversion method of any one of claims 1 to 8.

Description

Shale layer physical and mechanical property inversion method, equipment and medium Technical Field The invention relates to the technical field of rock mass mechanics analysis, in particular to a shale layer physical and mechanical property inversion method, equipment and medium. Background In the fields of unconventional oil gas development, deep rock mass engineering and underground reservoir construction, the mechanical properties of shale layered rock mass are directly related to engineering safety and reservoir reconstruction effect, and are core elements of engineering design and reservoir evaluation. The shale is internally and widely developed into a layer surface and a weak interlayer, is a typical strong anisotropic rock mass, key parameters such as elastic modulus, tensile strength, fracture toughness and the like are obviously changed along with the layer angle, the shale with different layer angles has obvious damage modes and crack propagation paths, and the layer surface often becomes a crack initiation starting point and a crack propagation leading path, so that the complexity of the mechanical response of the rock mass is increased. At present, the acquisition mode aiming at the mechanical properties of shale layers generally comprises (1) preparing a plurality of groups of samples under different bedding angles, measuring overall mechanical parameters through three-point bending, brazilian splitting, uniaxial/triaxial compression and other tests, (2) tracking crack propagation paths and crack tip positions by combining digital image Correlation (DIGITAL IMAGE Correlation, DIC), acoustic emission (Acoustic Emission, AE) or high-speed photography and other means, obtaining parameters by utilizing fracture mechanical models or finite element inversion, and (3) performing empirical fitting on bedding control damage based on load-displacement curves, peak strength or damage morphology. However, for strong anisotropic shale, cracks are easy to deflect along the layer, branch or intermittently jump, the mechanical parameters of the whole shale are obtained by the method, the sectional identification according to the layer interval is difficult to realize in the primary fracture process, and the difference of mechanical properties of the cracks when the cracks are expanded in different layer intervals cannot be reflected. Disclosure of Invention The invention aims to provide a shale layer physical and mechanical property inversion method, equipment and medium, which can solve the problem that the mechanical properties of different layers of shale during the expansion of the interval can not be obtained. In order to solve the technical problems, the embodiment of the invention provides a shale layer physical and mechanical property inversion method, which comprises the following steps: Establishing a bedding geometrical model according to the geometrical size and bedding interval of the target shale; Acquiring a mechanical signal and a generated electric signal when the target shale is broken under external applied force; determining a plurality of characteristic events of the electric signal by identifying peaks, peak clusters and silence areas in the electric signal, dividing the fracture process of the target shale into a plurality of time intervals according to the plurality of characteristic events and the layer-by-layer geometric model, wherein each time interval corresponds to the expansion stage of the fracture crack of the target shale in one layer-by-layer interval; determining the equivalent path length of each layer interval crack according to the layer geometrical model, and determining the average expansion speed of each layer interval crack according to the equivalent path length and the time difference between adjacent characteristic events; According to the mechanical signals and the bedding geometrical model, determining stress intensity factors of each bedding interval of the target shale in the fracture process; And determining the equivalent fracture energy and fracture toughness of each interval of the target shale in the fracture process according to the stress intensity factor and the average expansion speed and through the energy balance relation of the intervals in the fracture process. Further, the equivalent fracture energy of each interval of the target shale layer in the fracture process is determined by the following formula: ; ; ; In the formula, For the equivalent fracture energy of the current interval of the target shale in the fracture process,For the average propagation speed of the crack in the current interval,For the poisson ratio of the target shale, a is a preset correction coefficient,In order to correspond to the equivalent path length,For the time difference between adjacent feature events,For the wave velocity of the rayleigh wave,In order to achieve the wave velocity of the longitudinal wave,As a factor of the intensity of the stress,Is the equivalent