Pulsation visualization conventional triaxial fracturing rock sample testing system

Abstract

The invention discloses a pulsation visualization conventional triaxial fracturing rock sample testing system, which comprises a conventional triaxial device, a loading device, a pulsation generation device, a calculation control center and a data acquisition system, and is characterized in that the conventional triaxial device is prepared from a transparent material; the loading device is connected with the conventional triaxial device; the pulsation generating device provides pulsation liquid to the interior of the rock sample through the fracturing pipe; the calculation control center is connected and communicated with the loading device and the pulsation generating device; the data acquisition system comprises a CT scanner and a digital speckle module, the CT scanner scans a rock sample through a conventional three-axis device made of a transparent material, scans an internal slice of the rock sample in real time and performs three-dimensional reconstruction to form a three-dimensional, three-dimensional, visual and digital rock, and monitors the crack propagation process in real time; the digital speckle module captures speckle patterns on the surface of a rock sample through a camera, traces crack initiation and expansion paths and speeds, and reveals a rock failure mechanism.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanical property research, in particular to a pulsation visualized conventional triaxial fracturing rock sample testing system. Background Art

[0002] Hydraulic fracturing, as a coal rock fracturing technology, can construct a dense coal rock fracture network, thereby transforming and reducing the integrity of the rock mass. It is widely used in the coal mining field, such as roof pressure relief along the empty tunnel, promoting the collapse of the hard roof, promoting the venting of the hard coal seam, promoting the fracture of the fault zone and the collapse column, and promoting the seepage of coal gas. As a new fracturing technology, pulsating fracturing can use periodic pulse water to act on the coal rock mass, causing fatigue damage to the coal rock mass, effectively reducing the fracture initiation pressure, activating, expanding and connecting the hidden and micro cracks inside the coal rock mass, forming a new fracture network, and gradually being used in the coal mining field.

[0003] However, when studying pulsation indoor tests, pulsation fracturing tests are usually conducted on large-sized rock samples, which are expensive. In addition, since the triaxial clamping device is often made of opaque metal materials such as stainless steel, the means of monitoring the structure and expansion direction of the fracturing cracks during the fracturing process are extremely limited. The pulsation fracturing effect can only rely on the observation of the crack surface after the fracturing is completed, and it is difficult to intuitively monitor the pulsation fracturing effect in real time and effectively during the fracturing process. Summary of the invention

[0004] The purpose of the present invention is to provide a pulsating visualized conventional triaxial fracturing rock sample testing system, which can perform all-round monitoring of the surface, internal, macroscopic and microscopic cracks of the fracturing rock sample, provide a sign for the final rupture of the rock sample, and conduct a comprehensive analysis of the fracturing effect.

[0005] The technical solution of the present invention is:

[0006] A pulsation visualized conventional triaxial fracturing rock sample testing system comprises: a conventional triaxial device for clamping a rock sample, the rock sample being preset with a hole, the conventional triaxial device being made of a transparent material, and the transparent material being able to ensure that X-rays penetrate into the inner cavity of the conventional triaxial device; a loading device connected to the conventional triaxial device and used to provide confining pressure and axial pressure to the conventional triaxial device; a pulsation generating device having a fracturing tube, the fracturing tube entering the inner cavity of the conventional triaxial device and being inserted into a preset hole on the rock sample, and providing pulsating fluid to the inside of the rock sample through the fracturing tube; the pulsation generating device is controlled by a computer ACTS module control software, the software can adjust the pulsating water flow frequency and pulsating waveform, and adjust the pulsating amplitude by an amplitude adjustment valve, the pulsation number can be applied in the software and the pulsating water pressure can be recorded in real time, so as to achieve the effect of accurate real-time control and stable output of pulsating water flow. A computing control center is connected and communicated with the loading device and the pulsation generating device; and a data acquisition system, including: a CT scanner, which is connected and communicated with the computing control center. The CT scanner can non-destructively obtain three-dimensional information of the internal structure of the rock, and is particularly suitable for studying complex features such as pores, crack distribution and fluid migration. The CT scanner has a ray source and a detector. A conventional three-axis device is arranged between the ray source and the detector. The conventional three-axis device, the ray source and the detector form a straight line. The ray source scans the rock sample through the conventional three-axis device made of transparent material, and the detector is used to receive the scanning signal; an X-ray source emits X-rays to the three-axis cavity. Since the three-axis device is made of sapphire material, the X-rays can effectively penetrate and project onto the detector. The detector can scan the internal slices of the rock sample in real time and perform three-dimensional reconstruction by sending data to the computer and processing through software, forming a three-dimensional, stereoscopic, intuitive, digital rock, and real-time monitoring of the crack expansion process. Digital speckle module, the digital speckle module can capture the speckle pattern on the surface of the rock sample through a camera, track the crack initiation, expansion path and speed, and reveal the rock failure mechanism, including: digital speckle pattern, set on the surface of the rock sample; image collector, set on one side of the conventional three-axis device, used to collect the digital speckle pattern on the surface of the rock sample, the image collector is connected and communicated with the computing control center, used to send the collected digital speckle pattern to the computing control center, and the collected digital speckle pattern is analyzed and compared by the computing control center. In the data acquisition system, the digital speckle technology first prepares a speckle pattern on the surface of the rock sample, takes pictures and records it at fixed intervals through a high-definition camera and saves it to the computer, uses DIC software to match the collected speckle images, finds the position changes of corresponding points in the image before and after deformation, and processes them. Since the fracture position of the rock sample will inevitably cause its displacement change, based on this, the fracture law of the surface of the rock sample during the fracturing process can be obtained.

[0007] Furthermore, the method for producing digital speckle on the surface of the rock sample includes: spraying a layer of white paint film evenly on the surface of the rock sample; after the white paint film is dried, using a black water-based pen to evenly apply dots on the surface of the white paint film to form a speckle pattern.

[0008] Furthermore, the data acquisition module also includes: an acoustic emission device, which is connected and communicated with the computing control center, and the acoustic emission device includes: a probe, which is made of ceramic material and will not affect the traditional CT scanner, and is set on the upper core plug and the lower core plug of the conventional three-axis device to capture the acoustic wave signal generated by the crack initiation; an acoustic emission amplifier, which is connected to the probe through a data line to amplify the captured acoustic wave signal. During the fracturing process, the acoustic emission device sends the acoustic wave signal data of the crack rupture to the computing control center, and records the sound of the rock sample rupture during the pulsating fracturing process and locates and records the rupture site in real time.

[0009] Furthermore, the transparent material is sapphire. Sapphire is a transparent material with high hardness, high density and bright glass luster. It can resist physical wear and scratches and exhibits extremely high chemical stability. Compared with other transparent materials, its high pressure resistance, high stability and long life can effectively support the pulsating fracturing experiment.

[0010] Furthermore, the computing control center is equipped with a display assembly for displaying images and digital speckle patterns acquired by the CT scanner.

[0011] Furthermore, the loading device is a constant speed and constant pressure loading device. The constant speed and constant pressure pump draws water from the water tank through a pipeline, and forms a constant speed or constant flow water output through the constant speed and constant pressure pump including a multi-interface control panel. The constant speed and constant pressure pump is a double-cylinder pump, which can realize the working mode of constant flow and constant pressure of pump A, constant flow and constant pressure of pump B, and constant flow and constant pressure of pump AB, and stably output water flow to the transfer valve. The switch is controlled by the transfer valve to realize the application of axial pressure, confining pressure, and water pressure.

[0012] Furthermore, the image collector is a high-definition camera, and the high-definition camera collects digital speckle images on the surface of the rock sample at fixed intervals. The time for the high-definition camera to collect digital speckle images is 1 second.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention uses a transparent sapphire material to make a conventional three-axis device. Since the conventional three-axis device is made of a transparent material, the present invention can emit X-rays to the three-axis cavity through an X-ray source, and the X-rays can effectively penetrate and project onto the detector. The detector can scan the internal slices of the rock sample in real time and perform three-dimensional reconstruction by sending data to a computer and processing through software, forming a three-dimensional, stereoscopic, intuitive, and digital rock, and real-time monitoring of the crack expansion process;

[0015] Based on the transparent conventional triaxial device made of transparent materials, the present invention prepares speckle patterns on the surface of rock samples, takes photos and records them with a high-definition camera at fixed intervals and saves them in a computer, uses DIC software to match the collected speckle images, finds the position changes of corresponding points in the images before and after deformation, and processes them. According to the displacement changes of the scattered spots caused by the fracture position of the rock sample, the surface fracture law of the rock sample during the fracturing process is analyzed, and the macroscopic surface cracks and internal cracks during the fracturing process are recorded and monitored.

[0016] At the same time, the present invention uses acoustic emission technology to locate and monitor the sound waves generated by the rupture of micro and hidden cracks during the fracturing process, thereby realizing all-round monitoring of crack rupture during the fracturing process and facilitating the evaluation of the experimental effect.

[0017] The transparent material used to prepare the conventional triaxial device of the present invention is sapphire material, and the conventional triaxial device is made of sapphire material as a whole. Sapphire is not only a transparent material, but also has the characteristics of high hardness, high density and bright glass luster, can resist physical wear and scratches, and exhibits extremely high chemical stability. Compared with other transparent materials, its high compressive resistance, high stability and long life can effectively support the experiment of pulsating fracturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0019] Figure 2 It is a schematic diagram of the structure of a conventional three-axis device of the present invention.

[0020] Figure 3 It is a schematic diagram of the structure of the CT scanner of the present invention and a conventional three-axis device.

[0021] Figure 4 This is a structural diagram of the acoustic emission probe arrangement of the present invention.

[0022] Among them, 1. conventional triaxial device, 11. core, 12. upper core plug, 13. lower core plug, 14. confining pressure injection port, 15. axial pressure injection port, 2. loading device, 21. water tank, 22. transfer valve, 3. pulsation generating device, 31. fracturing pipe, 4. computing control center, 5. CT scanner, 51. X-ray source, 52. detector, 6. digital speckle module, 61. image collector, 62. speckle pattern, 7. acoustic emission device, 71. probe. DETAILED DESCRIPTION

[0023] Combine the following Figures 1 to 4 , the specific embodiments of the present invention are described in detail. In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0024] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0025] It should be noted that the circuit connections involved in the present invention all adopt conventional circuit connection methods and do not involve any innovation.

[0026] Example

[0027] A pulsating visualized conventional triaxial fracturing rock sample testing system comprises: a conventional triaxial device 1, a loading device 2, a pulsating device 3, a computing control center 4 and a data acquisition system, wherein the conventional triaxial device 1 is used for clamping the rock sample, the rock sample is preset with a hole, the conventional triaxial device 1 is made of a transparent material, and the transparent material can ensure that X-rays penetrate into the inner cavity of the conventional triaxial device 1; the loading device 2 is connected to the conventional triaxial device 1, and is used to provide confining pressure and axial pressure to the conventional triaxial device 1; the pulsating device 3 has a fracturing tube 31, the fracturing tube 31 enters the inner cavity of the conventional triaxial device 1, and is inserted into the preset hole on the rock sample, and pulsating fluid is provided to the inside of the rock sample through the fracturing tube 31; the pulsating device 3 is controlled by a computer ACTS module control software, the software can adjust the pulsating water flow frequency and pulsating waveform, and adjust the pulsating amplitude through an amplitude adjustment valve, the software can apply the pulsation number and record the pulsating water pressure in real time, so as to achieve the effect of accurate real-time control and stable output of pulsating water flow. The computing control center 4 is connected and communicated with the loading device 2 and the pulsation generating device 3; the data acquisition system includes: a CT scanner 5 and a digital speckle module 6. The CT scanner 5 is connected and communicated with the computing control center 4. The CT scanner 5 can non-destructively obtain three-dimensional information of the internal structure of the rock, and is particularly suitable for studying complex features such as pores, crack distribution and fluid migration. The CT scanner 5 has a ray source and a detector 52. The conventional three-axis device 1 is arranged between the ray source and the detector 52. The conventional three-axis device 1, the ray source and the detector 52 form a straight line. The ray source passes through the conventional three-axis device 1 made of transparent material to scan the rock sample, and the detector 52 is used to receive the scanning signal; the X-ray source 51 emits X-rays to the three-axis cavity. Since the three-axis device is made of sapphire material, the X-rays can effectively penetrate and project onto the detector 52. The detector 52 can scan the internal slices of the rock sample in real time and perform three-dimensional reconstruction by sending data to the computer and processing through software, forming a three-dimensional, stereoscopic, intuitive, digital rock, and real-time monitoring of the crack expansion process. The digital speckle module 6 captures the speckle pattern 62 on the surface of the rock sample through a camera, tracks the crack initiation, expansion path and speed, and reveals the rock failure mechanism. The digital speckle module 6 includes: a digital speckle pattern 62 and an image collector 61. The digital speckle pattern 62 is set on the surface of the rock sample; the image collector 61 is set on one side of the conventional triaxial device 1, and is used to collect the digital speckle pattern 62 on the surface of the rock sample. The image collector 61 is connected and communicated with the computing control center 4, and is used to send the collected digital speckle pattern 62 to the computing control center 4, and the collected digital speckle pattern 62 is analyzed and compared by the computing control center 4. In the data acquisition system, the digital speckle technology first prepares the speckle pattern 62 on the surface of the rock sample, takes pictures and records it through a high-definition camera at fixed intervals and saves it in a computer, uses DIC software to match the collected speckle images, finds the position changes of corresponding points in the image before and after deformation, and processes them.Since the fracture position of the rock sample will inevitably cause its displacement change, the fracture law of the rock sample surface during the fracturing process can be obtained based on this.

[0028] In some embodiments, the method for producing digital speckle on the surface of a rock sample includes: spraying a layer of white paint film evenly on the surface of the rock sample; after the white paint film is dried, using a black water-based pen to evenly apply dots on the surface of the white paint film to form a speckle pattern 62 .

[0029] In some embodiments, the data acquisition module further includes: an acoustic emission device 7, which is connected to the computing control center 4 for communication, and the acoustic emission device 7 includes: a probe 71, which is made of ceramic material to avoid affecting the traditional CT scanner 5, and is arranged on the upper core plug 12 and the lower core plug 13 of the conventional triaxial device 1, and is used to capture the acoustic wave signal generated by the initiation of the crack; an acoustic emission amplifier, which is connected to the probe 71 through a data line to amplify the captured acoustic wave signal. During the fracturing process, the acoustic emission device 7 sends the acoustic wave signal data of the crack rupture to the computing control center 4, and the cracking sound of the rock sample during the pulsating fracturing process is recorded and the ruptured part is located and recorded in real time.

[0030] In some embodiments, the transparent material is sapphire. The entire conventional triaxial device 1 is made of sapphire material, has a confining pressure injection port 14 and an axial pressure injection port 15, and the load is applied through the loading device 2. According to the size of the existing conventional triaxial device 1, the relevant sapphire material accessories are customized in the factory. Sapphire is a transparent material with high hardness, high density and bright glass luster. It can resist physical wear and scratches and exhibits extremely high chemical stability. Compared with other transparent materials, its high pressure resistance, high stability and long life can effectively support the experiment of pulsating fracturing.

[0031] In some embodiments, the computing control center 4 is configured with a display assembly for displaying the image and the digital speckle pattern 62 acquired by the CT scanner 5 .

[0032] In some embodiments, the loading device 2 is a constant speed and constant pressure loading device 2. The constant speed and constant pressure pump draws water from the water tank 21 through a pipeline, and forms a constant speed or constant flow water output through the constant speed and constant pressure pump including a multi-interface control panel. The constant speed and constant pressure pump is a double-cylinder pump, which can realize the working mode of constant flow and constant pressure of pump A, constant flow and constant pressure of pump B, and constant flow and constant pressure of pump AB, and stably outputs water flow to the transfer valve 22. The switch is controlled by the transfer valve 22 to realize the application of axial pressure, confining pressure, and water pressure.

[0033] In some embodiments, the image collector 61 is a high-definition camera, which collects digital speckle images on the surface of the rock sample at fixed intervals. The time for the high-definition camera to collect digital speckle images is 1 second.

[0034] The above disclosures are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A pulsation visualized conventional triaxial fracturing rock sample testing system, characterized in that: include: A conventional triaxial device (1) is used to clamp a rock sample, the rock sample is preset with a hole, the hole is used to fix a fracturing pipe (31), the conventional triaxial device (1) is made of a transparent material, and the transparent material can ensure that X-rays penetrate into the inner cavity of the conventional triaxial device (1); Computing control center (4); The data acquisition system comprises: a CT scanner (5) and a digital speckle module (6), wherein the CT scanner (5) is connected to the computing control center (4) for communication, the CT scanner (5) has a ray source and a detector (52), a conventional triaxial device (1) is arranged between the ray source and the detector (52), the conventional triaxial device (1), the ray source and the detector (52) form a straight line, and the detector (52) is used to receive scanning signals; the digital speckle module (6) comprises: a digital speckle pattern (62) and an image collector (61), wherein the digital speckle pattern (62) is arranged on the surface of a rock sample, the image collector (61) is arranged on one side of the conventional triaxial device (1) and is used to collect the digital speckle pattern (62) on the surface of the rock sample, the image collector (61) is connected to the computing control center (4) for communication, and is used to send the collected digital speckle pattern (62) to the computing control center (4), and the computing control center (4) is used to analyze and compare the collected digital speckle pattern (62).

2. A pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: The method for producing a digital speckle pattern (62) on a rock sample surface comprises: Spray a thin film of white paint evenly on the surface of the rock sample; After the white paint film is dry, a black water-based pen is used to evenly apply dots on the surface of the white paint film to form a speckle pattern (62).

3. A pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: The data acquisition module further comprises: an acoustic emission device (7) connected to the computing control center (4) for communication, the acoustic emission device (7) comprising: a probe (71) made of ceramic material, arranged on an upper core plug (11) and a lower core plug (11) of a conventional triaxial device (1) for capturing acoustic wave signals generated by crack initiation; and an acoustic emission amplifier connected to the probe (71) via a data line for amplifying the captured acoustic wave signals.

4. The pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: The transparent material is sapphire.

5. The pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: The computing control center (4) is equipped with a display assembly for displaying images and digital speckle patterns (62) acquired by the CT scanner (5).

6. The pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: It also includes a loading device (2) connected to the conventional triaxial device (1) and connected to a computing control center (4) for communication, and used to provide confining pressure and axial pressure to the conventional triaxial device. The loading device (2) is a constant speed and constant pressure loading device (2).

7. The pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: The image collector (61) is a high-definition camera, which collects digital speckle images of the surface of the rock sample at fixed intervals.

8. The pulsation visualized conventional triaxial fracturing rock sample testing system according to claim 1, characterized in that: One end of the fracturing pipe (31) away from the rock sample is connected to a pulsation generating device (3), and the pulsation generating device (3) is connected to communicate with the computer control center (4).

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