Fracture instability test device and method equipped with industrial CT (Computed Tomography) scanning
By equipping a fracture instability testing device with industrial CT scanning, the problem of experimental environment control in high-pressure fluid injection-induced fracture zone frictional instability testing was solved, enabling real-time data recording and signal waveform collection, thus improving the comprehensiveness and analytical effectiveness of the test data.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-07
- Publication Date
- 2026-05-08
AI Technical Summary
Existing technologies struggle to precisely control the confining pressure and fluid pressure in high-pressure fluid injection-induced fracture zone friction instability tests, and lack visualization studies and acoustic emission data collection.
A fracture instability testing device equipped with industrial CT scanning, including a core holder, X-ray source and detector, is used to record data of the friction instability test process in real time through CT scanning, and to collect signal waveforms of the fracture surface during the sliding instability process.
It enables full-time and comprehensive data recording of high-pressure fluid injection-induced fracture zone frictional instability tests, improving the comprehensiveness of test data and analysis results.
Smart Images
Figure CN121994583A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rock mechanics testing technology, specifically to a fracture instability testing device equipped with industrial CT scanning, and a fracture instability testing method equipped with industrial CT scanning. Background Technology
[0002] The problem of frictional instability induced by high-pressure fluid injection in fracture zones has gradually attracted attention. In understanding the frictional instability and its mechanical mechanism induced by this engineering operation, laboratory experiments play an important role. As the most basic and commonly used method, laboratory experiments can obtain the sliding characteristics of natural fracture surfaces through analogy and other methods. In previous experiments on the frictional instability of fracture zones, polycarbonate plates or plexiglass were mainly used. These homogeneous materials are significantly different from rock-like materials. In addition, it is difficult to separate the confining pressure system and the fluid pressure system during the experiment, making it difficult to accurately control the confining pressure and fluid pressure of the experimental environment. Furthermore, traditional experimental methods lack visualization of the experimental process and the collection of acoustic emission data during the sliding process. Summary of the Invention
[0003] To enable more comprehensive data analysis of the frictional instability problem induced by high-pressure fluid injection in fracture zones, this invention provides a fracture instability testing device and method equipped with industrial CT scanning. The device and method can perform phased CT scanning during the frictional instability test and collect signal waveforms of the fracture surface during the sliding instability process, thus achieving full-time and comprehensive data recording of the frictional instability test induced by high-pressure fluid injection in fracture zones.
[0004] The technical solution adopted by this invention to solve its technical problem is:
[0005] A fracture instability testing device equipped with industrial CT scanning includes a core holder, a radiation source, and a detector. The core holder is located between the radiation source and the detector. The core holder contains a loading cylinder, an upper pressure cap, and a lower pressure cap. The loading cylinder is in an upright position. The lower part of the upper pressure cap is fixedly fitted inside the upper end of the loading cylinder, and the upper part of the lower pressure cap is fixedly fitted inside the lower end of the loading cylinder. The upper pressure cap is fitted with a loading piston and an upper plug arranged vertically, and the lower pressure cap is fitted with a lower plug. The upper plug and the lower plug can clamp the test sample. The radiation emitted by the radiation source can pass through the test sample and reach the detector.
[0006] A fracture instability testing method equipped with industrial CT scanning, wherein the fracture instability testing method equipped with industrial CT scanning employs the aforementioned fracture instability testing device equipped with industrial CT scanning, and the fracture instability testing method equipped with industrial CT scanning includes the following steps in sequence:
[0007] Step 1: Install the test sample between the upper and lower plugs, and apply confining pressure and axial pressure to the test sample;
[0008] Step 2: Increase the axial pressure on the test sample and observe the trend of the axial pressure curve. When the rate of increase of axial stress gradually slows down, the test sample reaches the critical slip instability state, and the loading piston stops loading.
[0009] Step 3: Inject high-pressure fluid through the upper or lower pressure channel. The radiation emitted by the radiation source passes through the test sample and is directed towards the detector, which receives the radiation.
[0010] The beneficial effects of this invention are: by using industrial CT scanning, acoustic reception and other means, it is possible to scan the phased evolution results of the test process, and to collect the signal waveforms of the fracture surface during the sliding instability process. It is possible to achieve full-time and comprehensive data recording of the high-pressure fluid injection-induced fracture zone friction instability test, and to apply digital and geophysical methods to the processing of rock mechanics test results, thereby improving the comprehensiveness of test data and analysis results. Attached Figure Description
[0011] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0012] Figure 1 This is a schematic diagram of a core holder.
[0013] Figure 2 This is a schematic diagram of the fracture instability testing device equipped with industrial CT scanning as described in this invention.
[0014] Figure 3 This is a cross-sectional view of the loading piston.
[0015] Figure 4 This is a three-dimensional schematic diagram of the upper pressure cap.
[0016] Figure 5 This is a cross-sectional view of the upper pressure cap.
[0017] Figure 6 This is a 3D schematic diagram of the pressure cap.
[0018] Figure 7 This is a cross-sectional view of the pressure cap.
[0019] Explanation of reference numerals in the attached figures:
[0020] 1. Core holder; 2. X-ray source; 3. Detector; 4. Test sample;
[0021] 11. Loading top cover; 12. Loading piston; 13. Upper pressure cap; 14. Pressure sensor; 15. Upper plug; 16. Loading cylinder; 17. Rubber sleeve; 18. Lower plug; 19. Lower pressure cap; 110. Fixing ring; 111. Base;
[0022] 1101. Piston loading chamber; 1102. Axial pressure pressurization channel;
[0023] 1301, Axial through hole; 1302, Radial through hole;
[0024] 1501. Upper mounting hole; 1502. Upper pressure channel; 1503. Radial notch;
[0025] 1601. Cylinder wall; 1602. Internal space; 1603. Annular cavity;
[0026] 1801, Lower mounting hole; 1802, Lower pressure testing channel;
[0027] 1901, Lower axial through hole; 1902, Confining pressure channel;
[0028] 11101. Upper plate; 11102. Lower plate; 11103. Support leg. Detailed Implementation
[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0030] For ease of understanding and description, the following description of the present invention uses absolute positional relationships. Unless otherwise specified, the directional term "above" indicates... Figure 2 The direction above, the directional word "down" indicates Figure 2 The lower side of the middle, the directional word "left" indicates Figure 2 The left side of the direction, the directional word "right" indicates Figure 2 The right-hand direction in the text, the directional word "front" indicates perpendicular to. Figure 2 The direction of the paper and pointing inwards from the paper; the directional word "back" indicates perpendicular to the paper. Figure 2 The orientation of the paper is directed towards the outer edge of the paper. This invention is described from the perspective of a reader or user, but the aforementioned directional terms should not be construed as limiting the scope of protection of this invention. Regarding the dimensions and angles of the components, those skilled in the art can determine them specifically based on actual needs or a limited number of experiments.
[0031] like Figure 1 and Figure 2As shown in the embodiment of the present invention, a fracture instability testing device equipped with industrial CT scanning includes a core holder 1, a radiation source 2, and a detector 3. The core holder 1 is located between the radiation source 2 and the detector 3. The core holder 1 includes a loading cylinder 16, an upper pressure cap 13, and a lower pressure cap 19. The loading cylinder 16 is in an upright state. The lower part of the upper pressure cap 13 is fixedly sleeved inside the upper end of the loading cylinder 16, and the upper part of the lower pressure cap 19 is fixedly sleeved inside the lower end of the loading cylinder 16. The upper pressure cap 13 is fitted with a loading piston 12 and an upper plug 15 arranged vertically, and the lower pressure cap 19 is fitted with a lower plug 18. The upper plug 15 and the lower plug 18 can clamp the test sample 4. The radiation emitted by the radiation source 2 can pass through the test sample 4 and be directed towards the detector 3.
[0032] The loading cylinder 16 includes a cylinder wall 1601 and an internal space 1602. The internal space 1602 contains a rubber sleeve 17. The upper end of the rubber sleeve 17 is fitted over the lower end of the upper plug 15, and the lower end of the rubber sleeve 17 is fitted over the upper end of the lower plug 18. The rubber sleeve 17 is an upright cylindrical structure. The rubber sleeve 17 can be fitted onto the test sample 4. An annular cavity 1603 is formed between the rubber sleeve 17 and the loading cylinder 16, which isolates the sample from the confining pressure medium. Sealing rings are provided at the contact points between the upper plug 15 and the lower plug 18 and the tube ends of the rubber sleeve 17. The sealing rings cover a wide area, avoiding errors caused by stress concentration at the sample ends.
[0033] The radiation emitted by radiation source 2 is a conventional radioactive radiation, such as X-rays, gamma rays, or beta rays. Preferably, the radiation emitted by radiation source 2 is X-rays, which can penetrate the test sample 4 and reach detector 3. Detector 3 is a high-sensitivity detector, meaning that radiation source 2 and detector 3 can use existing CT scanning equipment, and detector 3 can collect CT scan signals from test sample 4.
[0034] The axes of the loading cylinder 16, the rubber sleeve 17, the test sample 4, the upper pressure cap 13, the lower pressure cap 19, the loading piston 12, the upper plug 15, and the lower plug 18 coincide. The upper pressure cap 13 and the lower pressure cap 19 are both upright cylindrical structures, while the loading piston 12, the upper plug 15, and the lower plug 18 are all upright columnar structures.
[0035] like Figures 1 to 3 As shown, the upper pressure cap 13 is threadedly connected to the loading cylinder 16. The upper part of the upper pressure cap 13 is located outside the loading cylinder 16. The upper pressure cap 13 contains an upper axial through hole 1301 and a radial through hole 1302. The loading piston 12 and the upper plug 15 are both located inside the upper axial through hole 1301. The radial through hole 1302 is located in the middle or upper part of the upper pressure cap 13 and outside the loading cylinder 16.
[0036] The loading piston 12 and the upper plug 15 are both clearance-fitted or transition-fitted with the upper pressure cap 13. The loading piston 12 and the upper plug 15 are both sealed to the upper pressure cap 13. The loading piston 12 and the upper plug 15 can move up and down relative to the upper pressure cap 13.
[0037] like Figure 1 and Figure 2 As shown, a pressure sensor 14 is provided between the loading piston 12 and the upper plug 15. The loading piston 12, pressure sensor 14 and upper plug 15 are connected in sequence from top to bottom. The pressure sensor 14 can measure the pressure value of the pressure applied by the loading piston 12 to the upper plug 15, that is, it is used to measure the axial pressure of the test system.
[0038] The pressure sensor 14 is positioned corresponding to the radial through-hole 1302, allowing it to pass through for easy installation and wiring. A controller is installed inside the control box, and data from the pressure sensor 14 can be recorded via a computer.
[0039] During the test, the axial pressure on the test sample 4 is transmitted to the pressure sensor 14 through the upper plug 15, which can realize the accurate measurement of axial pressure. After the data is transmitted to the microcomputer through the controller, the axial pressure can be servo controlled, so that the sample is in a human-controlled stress environment, which is convenient for in-situ CT scanning.
[0040] like Figure 2 , Figure 4 and Figure 5 As shown, a loading top cover 11 is externally connected to the upper end of the upper pressure cap 13. The loading top cover 11 is sealed to the upper pressure cap 13, forming a piston loading chamber 1101 between the loading top cover 11 and the loading piston 12. The loading top cover 11 contains an axial pressure channel 1102, through which pressurized fluid can enter the piston loading chamber 1101 and cause the loading piston 12 to move downward. The lower part of the loading top cover 11 is fitted inside the upper pressure cap 13, and the upper part of the loading top cover 11 is located outside the upper pressure cap 13. The loading top cover 11 is connected to the upper pressure cap 13 by bolts. The loading top cover 11 can limit the upward movement range of the loading piston 12 and the upper plug 15.
[0041] The fracture instability testing device equipped with industrial CT scanning also includes an axial pressure loading system. This system contains an electric hydraulic pump, whose hydraulic output port is connected to the axial pressure pressurization channel 1102. The electric hydraulic pump includes a servo motor. The axial loading system is controlled by a loading piston 12, which is connected to a microcomputer controller. The piston's movement speed is calculated based on the motor's rotational performance. At the start of the test, the loading piston 12 moves at a rate of 0.02 mm / min. The critical slip condition is determined by the curve measured by the pressure sensor 14 during the test, and the piston movement is stopped or servo control of the axial pressure is activated as needed. Under these conditions, an in-situ CT scan is performed on the sample.
[0042] The electric hydraulic pump pumps high-pressure liquid into the piston loading chamber 1101 through the axial pressure pressurization channel 1102 to apply axial pressure to the test sample 4. The axial pressure loading system is servo-controlled by a microcomputer sending commands. After the flow pressure reaches the set target value, the mechanical environment of the sample remains unchanged, and scanning can be performed.
[0043] like Figure 2 As shown, the lower pressure cap 19 is threadedly connected to the loading cylinder 16. The lower part of the lower pressure cap 19 is located outside the loading cylinder 16. The lower pressure cap 19 contains a lower axial through hole 1901. The lower plug 18 is located inside the lower axial through hole 1901. A fixing ring 110 is sleeved between the lower pressure cap 19 and the lower plug 18. The fixing ring 110 is threadedly connected to the lower pressure cap 19. The fixing ring 110 can prevent the lower plug 18 from moving downward. A confining pressure channel 1902 is provided inside the lower pressure cap 19. The upper end of the confining pressure channel 1902 communicates with the annular cavity 1603. The lower end of the confining pressure channel 1902 is located at the lower part of the side circumference of the lower pressure cap 19. The lower end of the confining pressure channel 1902 is located outside the loading cylinder 16.
[0044] The lower plug 18 and the lower pressure cap 19 are clearance-fitted or transition-fitted, and the lower plug 18 and the lower pressure cap 19 are sealed together. The lower plug 18 can move up and down relative to the lower pressure cap 19 within a certain range. Along the up and down direction, an annular protrusion is provided in the middle of the outer peripheral surface of the lower plug 18, and the inner diameter of the fixing ring 110 is smaller than the outer diameter of the annular protrusion.
[0045] like Figure 2 , Figure 6 and Figure 7As shown, the fracture instability testing device equipped with industrial CT scanning also includes a confining pressure loading system. This system is connected to the lower end of the confining pressure pressurization channel 1902. The confining pressure loading system can pump high-pressure gas into the annular cavity 1603 through the confining pressure pressurization channel 1902 to apply confining pressure to the test sample 4. In other words, the confining pressure loading system contains a gas pump. The confining pressure loading method uses gas pressurization, reducing the shielding effect of hydraulic oil on radiation.
[0046] The upper plug 15 contains an upper mounting hole 1501 and an upper pressure channel 1502. The upper mounting hole 1501 extends along the axial direction of the upper plug 15. The upper end of the upper mounting hole 1501 is open, and the lower end of the upper mounting hole 1501 is closed. The upper end of the upper plug 15 is provided with a radial notch 1503, which extends radially along the upper plug 15 and communicates with the upper mounting hole 1501. The lower end of the upper pressure channel 1502 is located on the lower end face of the upper plug 15, and the upper end of the upper pressure channel 1502 is located on the upper part of the side circumferential surface of the upper plug 15. The upper end of the upper pressure channel 1502 and the radial notch 1503 are both located in the upper axial through hole 1301, which can facilitate pipeline connection.
[0047] like Figure 2 As shown, the lower plug 18 contains a lower mounting hole 1801 and a lower pressure channel 1802. The lower mounting hole 1801 extends along the axial direction of the lower plug 18. The lower end of the lower mounting hole 1801 is in an open state, and the upper end of the lower mounting hole 1801 is in a closed state. The upper end of the lower pressure channel 1802 is located on the upper end face of the lower plug 18, and the lower end of the lower pressure channel 1802 is located on the lower end face of the lower plug 18.
[0048] High-pressure fluid can be injected through the upper pressure channel 1502 or the lower pressure channel 1802. For example, the upper end of the upper pressure channel 1502 is closed, and a pressure device is connected to the outside of the lower pressure channel 1802. The pressure device can pump pressurized fluid into the test sample 4 through the lower pressure channel 1802, causing the axial pressure inside the test sample 4 to rise. The lower diameter of the upper plug 15, the diameter of the test sample 4, and the upper diameter of the lower plug 18 are the same. This ensures that the sample is subjected to uniform force to the greatest extent and avoids test errors caused by stress concentration at the ends of the sample.
[0049] The axial loading system and fluid pressure control system (including the aforementioned pressurization device) enable precise control of pressure and movement speed. Once the flow pressure reaches the set target value, the mechanical environment of the sample remains constant, allowing for scanning operations. For example... Figure 2 As shown, acoustic wave receiving devices can be installed at the bottom of the upper mounting hole 1501 and at the top of the lower mounting hole 1801. The acoustic wave receiving devices are used to collect the acoustic wave signals and waveforms generated by the test sample 4 under axial pressure and confining pressure during the test.
[0050] For example, the acoustic receiving probe can be inserted into the upper mounting hole 1501 through the radial notch 1503 of the upper plug 15. The position of the acoustic receiving probe closest to the test sample 4 can, on the one hand, maximize the collection of signal changes caused by the slippage of the fracture surface in the test sample 4 during the test, and be used to collect waveform signals of different slippage types, providing a basis for forward and inverse modeling of the same type of test; on the other hand, it can maximize the integrity and safety of the acoustic receiving probe and increase the service life of the acoustic receiving probe.
[0051] The core holder 1 also includes a base 111, which has an upper plate 11101 and a lower plate 11102 spaced apart. Both the upper plate 11101 and the lower plate 11102 are circular ring structures. The lower pressure cap 19 sits on the upper plate 11101 and abuts against the upper plate 11101. The axis of the upper plate 11101, the axis of the lower plate 11102 and the axis of the lower pressure cap 19 coincide.
[0052] like Figure 2 As shown, the upper plate 11101 is sleeved outside the fixed ring 110. The inner diameter of the upper plate 11101 is larger than the outer diameter of the fixed ring 110. The upper plate 11101 and the lower plate 11102 are connected by multiple legs 11103 (e.g., by welding). The multiple legs 11103 are evenly spaced along the circumference of the upper plate 11101.
[0053] The following describes a fracture instability testing method equipped with industrial CT scanning. This method utilizes the aforementioned fracture instability testing device equipped with industrial CT scanning and includes the following steps:
[0054] Step 1: Install the test sample 4 between the upper plug 15 and the lower plug 18, and apply confining pressure and axial pressure to the test sample 4 to place the sample in a triaxial stress environment with equal triaxial stress. Specifically, the axial pressure loading system pumps high-pressure liquid into the piston loading chamber 1101, causing the loading piston 12 and the upper plug 15 to move downwards, and the upper plug 15 and lower plug 18 to clamp the test sample 4 (i.e., the core sample), providing axial pressure. The confining pressure loading system pumps high-pressure gas into the annular cavity 1603 to apply confining pressure to the test sample 4.
[0055] Test sample 4 is a standard cylindrical specimen with a diameter of 50 mm and a height of 100 mm, conforming to the specifications of the International Society for Rock Mechanics and the Rock Mechanics Specimen Standard. The specimen is wrapped with a rubber sleeve, forming an annular cavity between the specimen and the loading cylinder 16. During the test, the annular cavity is filled with high-pressure gas to provide a confining pressure environment for the specimen. Compared with the traditional confining pressure oil pressurization method, the gas reduces the shielding effect of the confining pressure environment on the X-ray signal, providing favorable conditions for the staged scanning during the loading process.
[0056] Step 2: Move the loading piston 12 downward at a rate of 0.02 mm / min, thereby driving the upper plug 15 to move downward synchronously, increasing the axial pressure of the test sample 4. During this process, observe the changing trend of the axial pressure curve recorded by the pressure sensor 14. When the rate of increase of axial stress gradually slows down, that is, when the slope of the stress curve approaches zero, for example, when the rate of increase of axial stress is less than 3%, it is considered that the test sample 4 has reached the critical slip instability state, and the loading piston 12 stops loading.
[0057] Step 3: The upper end of the upper pressure channel 1502 is closed. High-pressure fluid is injected into the test sample 4 through the lower pressure channel 1802 in a continuous or stepwise manner. The data from the pressure sensor 14 is observed and recorded. During the test, a CT scan of the test sample 4 can be performed at a selected time. That is, the rays emitted by the X-ray source 2 pass through the test sample 4 and are directed to the detector 3, which receives the rays. The detector 3 collects and analyzes the CT scan signal of the test sample 4. In addition, the acoustic signal and waveform generated by the test sample 4 during the test can be collected as needed.
[0058] Step 4: Stop the test when the pressure of the high-pressure fluid injected through the lower pressure channel 1802 is equal to the confining pressure.
[0059] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of protection of the present invention, should still fall within the scope of the present invention. Furthermore, the technical features, technical features and technical solutions, and technical solutions in the present invention can be freely combined and used.
Claims
1. A fracture instability testing device equipped with industrial CT scanning, characterized in that, The fracture instability test device equipped with industrial CT scanning includes a core holder (1), a radiation source (2), and a detector (3). The core holder (1) is located between the radiation source (2) and the detector (3). The core holder (1) contains a loading cylinder (16), an upper pressure cap (13), and a lower pressure cap (19). The loading cylinder (16) is in an upright state. The lower part of the upper pressure cap (13) is fixedly sleeved inside the upper end of the loading cylinder (16). The upper part of the lower pressure cap (19) is fixedly sleeved inside the lower end of the loading cylinder (16). The upper pressure cap (13) is fitted with a loading piston (12) and an upper plug (15) arranged vertically. The lower pressure cap (19) is fitted with a lower plug (18). The upper plug (15) and the lower plug (18) can clamp the test sample (4). The radiation emitted by the radiation source (2) can pass through the test sample (4) and be directed towards the detector (3).
2. The fracture instability testing device equipped with industrial CT scanning according to claim 1, characterized in that, The loading cylinder (16) contains a cylinder wall (1601) and an internal space (1602). The internal space (1602) contains a rubber sleeve (17). The upper end of the rubber sleeve (17) is fitted outside the lower end of the upper plug (15), and the lower end of the rubber sleeve (17) is fitted outside the upper end of the lower plug (18). The rubber sleeve (17) can be fitted outside the test sample (4). An annular cavity (1603) is formed between the rubber sleeve (17) and the loading cylinder (16). The radiation emitted by the radiation source (2) is X-ray.
3. The fracture instability testing device equipped with industrial CT scanning according to claim 1, characterized in that, The upper pressure cap (13) has an upright cylindrical structure. The upper pressure cap (13) is threadedly connected to the loading cylinder (16). The upper part of the upper pressure cap (13) is located outside the loading cylinder (16). The upper pressure cap (13) contains an upper axial through hole (1301) and a radial through hole (1302). The loading piston (12) and the upper plug (15) are both located inside the upper axial through hole (1301), and the radial through hole (1302) is located outside the loading cylinder (16).
4. The fracture instability testing device equipped with industrial CT scanning according to claim 3, characterized in that, A pressure sensor (14) is provided between the loading piston (12) and the upper plug (15). The pressure sensor (14) can measure the pressure applied by the loading piston (12) to the upper plug (15). The position of the pressure sensor (14) corresponds to the position of the radial through hole (1302). The pressure sensor (14) can pass through the radial through hole (1302).
5. The fracture instability testing device equipped with industrial CT scanning according to claim 3, characterized in that, The upper end of the upper pressure cap (13) is connected to a loading top cover (11). A piston loading chamber (1101) is formed between the loading top cover (11) and the loading piston (12). The loading top cover (11) contains an axial pressure pressurization channel (1102). The pressurized fluid can enter the piston loading chamber (1101) through the axial pressure pressurization channel (1102) and cause the loading piston (12) to move downward.
6. The fracture instability testing device equipped with industrial CT scanning according to claim 5, characterized in that, The fracture instability testing device equipped with industrial CT scanning also includes an axial pressure loading system, which contains an electric hydraulic pump. The hydraulic output port of the electric hydraulic pump is connected to the axial pressure pressing channel (1102), and the electric hydraulic pump contains a servo motor.
7. The fracture instability testing device equipped with industrial CT scanning according to claim 2, characterized in that, The lower pressure cap (19) has an upright cylindrical structure. The lower pressure cap (19) is threadedly connected to the loading cylinder (16). The lower part of the lower pressure cap (19) is located outside the loading cylinder (16). The lower pressure cap (19) contains a lower axial through hole (1901). The lower plug (18) is located inside the lower axial through hole (1901). A retaining ring (110) is sleeved between the lower pressure cap (19) and the lower plug (18). The retaining ring (110) and the lower pressure cap (19) Threaded connection, the fixing ring (110) can prevent the lower plug (18) from moving downward. The lower pressure cap (19) is provided with a confining pressure channel (1902). The upper end of the confining pressure channel (1902) is connected to the annular cavity (1603). The lower end of the confining pressure channel (1902) is located at the lower part of the side circumference of the lower pressure cap (19). The lower end of the confining pressure channel (1902) is located outside the loading cylinder (16).
8. The fracture instability testing device equipped with industrial CT scanning according to claim 3, characterized in that, The upper plug (15) contains an upper mounting hole (1501) and an upper pressure channel (1502). The upper end of the upper mounting hole (1501) is open, and the lower end of the upper mounting hole (1501) is closed. The upper end of the upper plug (15) is provided with a radial notch (1503), which communicates with the upper mounting hole (1501). The lower end of the upper pressure channel (1502) is located on the lower end face of the upper plug (15), and the upper end of the upper pressure channel (1502) is located on the upper part of the side circumferential surface of the upper plug (15). The upper end and radial notch (1503) are both located inside the upper axial through hole (1301); the lower plug (18) contains a lower mounting hole (1801) and a lower pressure channel (1802). The lower end of the lower mounting hole (1801) is open, and the upper end of the lower mounting hole (1801) is closed. The upper end of the lower pressure channel (1802) is located on the upper end face of the lower plug (18), and the lower end of the lower pressure channel (1802) is located on the lower end face of the lower plug (18); both the upper mounting hole (1501) and the lower mounting hole (1801) are equipped with sound wave receiving devices.
9. The fracture instability testing device equipped with industrial CT scanning according to claim 7, characterized in that, The core holder (1) also includes a base (111), which has an upper plate (11101) and a lower plate (11102) spaced apart. The upper plate (11101) has a circular structure, and the lower pressure cap (19) sits on the upper plate (11101). The upper plate (11101) is fitted outside the fixing ring (110). The upper plate (11101) and the lower plate (11102) are connected by multiple legs (11103), which are arranged at intervals along the circumference of the upper plate (11101).
10. A fracture instability testing method equipped with industrial CT scanning, characterized in that, The fracture instability testing method equipped with industrial CT scanning uses the fracture instability testing device equipped with industrial CT scanning as described in claim 1, and the fracture instability testing method equipped with industrial CT scanning includes the following steps in sequence: Step 1: Install the test sample (4) between the upper plug (15) and the lower plug (18), and apply confining pressure and axial pressure to the test sample (4); Step 2: Increase the axial pressure of the test sample (4) and observe the trend of the axial pressure curve. When the rate of increase of axial stress gradually slows down, the test sample (4) reaches the critical slip instability state, and the loading piston (12) stops loading. Step 3: Inject high-pressure fluid through the upper pressure channel (1502) or the lower pressure channel (1802). The radiation emitted by the radiation source (2) passes through the test sample (4) and is directed towards the detector (3), which receives the radiation.