Topological structure fractured rock sample hydraulic fracturing test device

Abstract

The utility model relates to the technical field of rock and soil geology tests, in particular to a hydraulic fracturing test device for a fractured rock sample with a topological structure, which comprises a sealing back plate, an observation panel and a hollow front plate, prestressed bolts are arranged on the inner sides of four corners of the surface of one side of the sealing back plate, and fastening nuts are arranged at the end parts of the surfaces of one sides of the prestressed bolts. A high-pressure water injection hole is formed in the middle of the surface of one side of the sealing back plate, an observation panel is arranged at the other end of the surface of one side of the prestressed bolt, and sealing rings are arranged in the middles of the surfaces of the inner sides of the sealing back plate and the observation panel; the hydraulic fracturing test device for the fractured rock sample with the topological structure is simple in structure, suitable for a common uniaxial testing machine and capable of being directly observed. According to the device, the mechanical structure is simplified, the design of the observation window is improved, water pressure can be effectively sealed, the crack expansion process can be clearly and reliably observed and recorded, and the overall test working efficiency is effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of rock and soil geological tests, in particular to a hydraulic fracturing test device for a topological structure fractured rock sample. Background Art

[0002] After retrieval of the Chinese patent document with the existing publication number CN118067528A, a small-size visual sandstone hydraulic fracturing test device and its test method are disclosed, including a sample holder, a confining pressure pump, an axial pressure pump, a camera device, a water injection pump, and a magnetic measurement device; the sample holder includes a transparent cavity, and a core sample is placed in the cylindrical cavity of the transparent cavity; a plug is arranged below the core sample in the cavity of the transparent cavity; a fracturing pipeline is arranged above the core sample in the cavity of the transparent cavity; an axial pressure through hole is arranged on the lower side surface of the transparent cavity, and the axial pressure through hole is connected to the axial pressure pump; a water injection through hole is arranged on the upper side surface of the transparent cavity, and the water injection pump is connected to the fracturing pipeline through a second high-pressure pipeline, and the second high-pressure pipeline passes through the water injection through hole; a confining pressure through hole is arranged on the side surface of the transparent cavity, and the confining pressure through hole is connected to the confining pressure pump. By adopting the device of the invention, the morphology of rock fractures and the evolution law of pore structures can be monitored in real time during the hydraulic fracturing process.

[0003] Experimental research in geotechnical engineering and geology is an important branch of rock mechanics and engineering geology, involving an in-depth understanding of the formation, development, and evolution mechanisms of rock mass fracture networks. In recent years, with the rapid development of infrastructure construction, underground engineering, resource exploration and other fields, the research demand for rock mass fracture networks has increased day by day. The research on fracture networks not only helps to predict and prevent catastrophic events (such as collapses and water inrushes) in rock mass engineering, but also has important significance in geothermal energy development, oil and gas reservoir exploitation, and groundwater resource management.

[0004] Traditional research on rock mass fractures mainly focuses on the mechanical behavior of single - crack and double - crack specimens. These studies provide an important basis for understanding the basic characteristics of fractured rock masses. This method involves pre - fabricating single - crack or double - crack specimens, conducting loading tests under laboratory conditions, and observing the crack propagation and evolution. Although such studies can provide some basic data, due to the overly simple fracture forms, they cannot reflect the true situation of complex fracture networks in actual rock masses. The fracture forms in actual rock masses are far more complex than single - crack and double - crack ones. The existence of topological combined fractures makes the mechanical behavior of rock masses more difficult to predict. Therefore, scholars have tried to reveal the evolution laws and mechanical properties of complex fracture networks through experimental and numerical simulation methods. In numerical research, scholars can use the finite - element method, discrete - element method, etc. to simulate the formation and development of complex fracture networks on computers. Numerical simulation can handle complex geometric and physical conditions, but its results highly depend on the selection of model parameters and the setting of initial conditions, and it is impossible to directly verify the authenticity of the simulation results. In experiments, a common problem is that the failure process of complex fracture - combination specimens is complex, and it is difficult to analyze the mechanism in non - directly observable test studies, and it is even hard to find quantitative laws. Most existing studies conduct comparative analysis through non - directly observable data in experiments and the failure modes of specimens before and after experiments. Therefore, it is of great significance to carry out experimental research on the evolution of fracture networks with complex fracture combinations and directly observe the crack initiation and propagation process. Currently, some research institutions have developed experimental methods or special equipment that can directly observe fracture propagation, such as using model specimens made of transparent materials and observing fracture propagation in real - time through optical methods. Or adopting complex loading device integration, relying on extremely complex testing systems. Although these devices can provide intuitive observation results, they are usually complex in structure, high in cost, require special - matching loading testing machines or have special requirements for loading equipment and lack generality. Summary of the Invention

[0005] The technical problem to be solved by the present utility model is to overcome the defects of the prior art and provide a hydraulic fracturing test device for fractured rock samples with topological structures, aiming to solve the technical problems that the existing experimental methods or special equipment for observing fracture propagation cannot achieve direct observation, have complex structures, high requirements for loading equipment, unreasonable design of observation windows, and poor generality.

[0006] To solve the above - mentioned technical problems, the present utility model provides the following technical solutions:

[0007] The utility model relates to a hydraulic fracturing test device for a topological structure fractured rock sample, which comprises a sealing back plate, an observation panel and a hollowed-out front plate. At the inner sides of the four corners of one side surface of the sealing back plate, prestressed bolts are arranged. At the end parts of one side surfaces of the prestressed bolts, fastening nuts are arranged. At the middle part of one side surface of the sealing back plate, a high-pressure water injection hole is arranged. At the other end of one side surface of the prestressed bolt, an observation panel is arranged. Sealing rings are arranged at the middle parts of the inner side surfaces of the sealing back plate and the observation panel. On one side surface of the observation panel, a hollowed-out front plate is arranged. At the inner sides of the four corners of one side surface of the hollowed-out front plate, bolt chucks are arranged.

[0008] As a further description of the above technical solution:

[0009] The sealing back plate, the observation panel and the hollowed-out front plate are connected and fixed through prestressed bolts. The heights of the sealing back plate and the hollowed-out front plate are both set to be 140 mm, and the widths are both set to be 175 mm. At the four corners of one side surface of the sealing back plate, 17-mm round holes are arranged.

[0010] As a further description of the above technical solution:

[0011] The prestressed bolt and the fastening nut are in threaded connection. The prestressed bolt is set as an external hexagon head high-strength bolt of grade 12.9 DIN933 / 931, with an outer diameter of 16 mm and a length of 130 mm. The sealing back plate and the high-pressure water injection hole are in threaded connection. A bolt connection hole corresponding to the high-pressure water injection hole is arranged at the center of the sealing back plate. The diameter of the high-pressure water injection hole is set to be 5 mm, and the depth is set to be 10 mm.

[0012] As a further description of the above technical solution:

[0013] The sealing back plate and the observation panel are assembled with the sealing ring in a splicing manner. The sealing ring is an O-ring with a rectangular cross section, and the material is set as a black fluororubber layer. The inner rectangular length of the sealing ring is 110 mm, the width is 45 mm, the outer rectangular length is 118 mm, the width is 53 mm, and the thickness is set to be 4 mm.

[0014] As a further description of the above technical solution:

[0015] Installation grooves are arranged on the inner sides of both the sealing back plate and the observation panel. The sealing ring is fixed through the installation grooves. The depths of the installation grooves on the inner sides of the sealing back plate and the observation panel are 2.5 mm, the widths are 4 mm, the inner widths are 45 mm, the outer widths are 53 mm, the inner heights are 110 mm, and the outer heights are 118 mm.

[0016] As a further description of the above technical solution:

[0017] The observation panel is set with a thickness of 40 mm and is composed of polycarbonate transparent plates. An observation window is provided in the middle of the hollow front plate. The observation window is designed with a slope, with a height of 110 mm and a width of 75 mm. The bolt bayonet is correspondingly set with the prestressed bolt. The length of the bolt bayonet is 29 mm, the width is 25 mm, and the hollow depth is set to 10 mm.

[0018] The utility model has the following beneficial effects:

[0019] In the utility model, there is a hydraulic fracturing test device for topological structure fractured rock samples that can be directly observed, with a simple structure and applicable to ordinary single-axis testing machines. This device not only simplifies the mechanical structure but also improves the design of the observation window, can effectively seal the water pressure, enables the fracture propagation process to be clearly and reliably observed and recorded, and effectively improves the overall test work efficiency. Description of the Drawings

[0020] The drawings are used to provide a further understanding of the utility model and constitute a part of the specification. Together with the embodiments of the utility model, they are used to explain the utility model and do not constitute a limitation to the utility model. In the drawings:

[0021] Figure 1 is a schematic side view of the overall structure of the utility model;

[0022] Figure 2 is a schematic sectional view of the overall structure of the utility model;

[0023] Figure 3 is a schematic top view of the overall structure of the utility model;

[0024] In the figure: 1, sealing back plate; 2, observation panel; 3, hollow front plate; 4, prestressed bolt; 5, fastening nut; 6, high-pressure water injection hole; 7, sealing ring; 8, bolt bayonet. Detailed Embodiments

[0025] The following describes the preferred embodiments of the utility model with reference to the drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the utility model and are not used to limit the utility model.

[0026] Among them, the same reference numerals in the drawings all refer to the same components.

[0027] Embodiment 1

[0028] Refer to Figures 1-3, an embodiment provided by the present utility model: a hydraulic fracturing test device for topological structure fractured rock samples, including a sealing back plate 1, an observation panel 2, and a hollowed front plate 3. At the inner sides of the four corners of one side surface of the sealing back plate 1, prestressed bolts 4 are provided. At the end of one side surface of the prestressed bolts 4, fastening nuts 5 are provided. In the middle of one side surface of the sealing back plate 1, a high-pressure water injection hole 6 is provided. At the other end of one side surface of the prestressed bolts 4, an observation panel 2 is provided. Sealing rings 7 are provided in the middle of the inner side surfaces of the sealing back plate 1 and the observation panel 2. On one side surface of the observation panel 2, a hollowed front plate 3 is provided. At the inner sides of the four corners of one side surface of the hollowed front plate 3, bolt bayonets 8 are provided.

[0029] The sealing back plate 1, the observation panel, and the hollowed front plate 3 are connected and fixed by prestressed bolts 4. The dimensions of the sealing back plate 1 and the hollowed front plate 3 are both 140 mm in height and 175 mm in width. At the four corners of one side surface of the sealing back plate 1, 17 mm round holes are provided.

[0030] The prestressed bolts 4 and the fastening nuts 5 are in threaded connection. The prestressed bolts 4 are set as external hexagon head high-strength bolts of model 12.9 grade DIN933 / 931, with an outer diameter of 16 mm and a length of 130 mm. The sealing back plate 1 and the high-pressure water injection hole 6 are in threaded connection. A bolt connection hole is provided at the center of the sealing back plate 1 corresponding to the high-pressure water injection hole 6. The diameter of the high-pressure water injection hole 6 is 5 mm and the depth is 10 mm.

[0031] The sealing back plate 1 and the observation panel 2 are assembled with the sealing ring 7. The sealing ring 7 is an O-ring with a rectangular cross-section, made of a black fluororubber layer. The inner rectangle length of the sealing ring 7 is 110 mm, the width is 45 mm, the outer rectangle length is 118 mm, the width is 53 mm, and the thickness is 4 mm.

[0032] Installation grooves are provided on the inner sides of both the sealing back plate 1 and the observation panel 2, and the sealing ring 7 is fixed through the installation grooves. The depth of the installation grooves on the inner sides of the sealing back plate 1 and the observation panel 2 is 2.5 mm, the width is 4 mm, the inner width is 45 mm, the outer width is 53 mm, the inner height is 110 mm, and the outer height is 118 mm.

[0033] The thickness of the observation panel 2 is set to 40 mm and is composed of a polycarbonate transparent plate. An observation window is provided in the middle of the hollowed front plate 3. The observation window adopts a slope design, with a height of 110 mm and a width of 75 mm. The bolt bayonet 8 corresponds to the prestressed bolt 4. The length of the bolt bayonet 8 is 29 mm, the width is 25 mm, and the hollowing depth is 10 mm.

[0034] Specifically, its structure consists of a sealing back plate 1, an observation panel 2, a hollowed front plate 2, prestressed bolts 4, fastening nuts 5, a high-pressure water injection hole 6, a sealing ring 7, and a bolt bayonet 8 to form a hydraulic fracturing test device for topological structure fractured rock samples, asFigure 1 As shown, the sealing mechanism of the hydraulic fracturing test device for topological structure fractured rock samples is simplified into three plates, namely the sealing back plate 1, the observation panel 2, and the hollowed-out front plate 2. The sealing back plate 1 and the hollowed-out front plate 2 are both composed of stainless steel plate parts, and the observation panel 2 is made of polycarbonate plate parts. In addition, it also includes a sealing ring 7, a prestressed bolt 4, and a fastening nut 5, making the overall structure simple. The hollowed-out front plate 2, the observation panel 2, the rock and soil sample, and the sealing back plate 1 are fixed together by the prestressed bolt 4 and the fastening nut 5. The prestressed bolt 4 is inserted sequentially from the bolt bayonet 8 at the four corners of the surface of the hollowed-out front plate 2 until the sealing back plate 1, and the fastening nut 5 is thread-fixed to the prestressed bolt 4 from one side surface of the sealing back plate 1. The sealing ring 7 deforms during the tightening process of the prestressed bolt 4 and undergoes a certain unloading during subsequent loading, generating a normal stress on the local surface of the sample to ensure stable sealing. The hollowed-out front plate 2 significantly expands the observable range, and the observation window adopts a slope design, reducing the light occlusion during lateral lighting, while reducing the weight of the device and facilitating the installation of the sample. It enables the direct observation of complex fracture networks in the hydraulic fracturing test device for topological structure fractured rock samples. By improving the observation window design and optimizing the sample fixing method, it can achieve the direct observation of topological structure fractured rock samples during the hydraulic fracturing process, clearly capture the initiation, propagation, and evolution process of fractures, and provide high-precision experimental data support; simplify the equipment structure, reduce costs, facilitate manufacturing and maintenance, and reduce the overall cost of the equipment. At the same time, this device is applicable to ordinary uniaxial testing machines, without the need for a dedicated loading system, and is convenient for wide application under ordinary laboratory conditions; improves the versatility of the equipment, is applicable to various types of samples and experimental conditions, has good versatility and adaptability, can meet different experimental requirements, and reduces the complexity and cost of researchers replacing equipment in different experiments; by adopting a flat sample and an optimized observation window design, it can provide deformation-free image data, reduce the difficulty of subsequent data processing, improve the quality and analysis efficiency of the observed data, enabling researchers to clearly and precisely observe and record the hydraulic fracturing process of complex fracture networks, and thus deeply understand the evolution mechanism of fracture networks.

[0035] Working principle: The loading system includes a uniaxial testing machine for mechanical experiments, a hydraulic fracturing test device for topological structure fractured rock samples with the test installed, a high-speed camera for observation, a high-pressure plunger pump, a pipeline for pumping fracturing fluid, a computer for controlling the testing machine, a computer for controlling the high-speed camera, and a computer for controlling the plunger pump. After installing the complex fractured sample in the hydraulic fracturing test device for topological structure fractured rock samples, it can be directly placed on an ordinary uniaxial compression testing machine for testing. Through the observation window of the hollowed-out front plate 2, the whole process of crack propagation can be directly observed by using a high-speed camera. This device has a simple structure, wide applicability, and strong versatility, is suitable for the study of various complex crack networks, and greatly improves the convenience of experiments and the observation accuracy. The hydraulic fracturing test device for topological structure fractured rock samples is conducive to supplementary lighting and image acquisition in optical testing, ensuring no obstruction during the observation process; the thickened transparent observation plate significantly improves the stiffness against warping, ensuring no deformation of the image during the observation process; the design of four high-strength bolts and self-fixing bolt holes greatly facilitates the installation of the sample and reduces the test preparation time; the optimized design of the fluororubber material sealing ring with a rectangular cross-section improves the sealing performance, ensuring no leakage during the hydraulic fracturing process, and effectively improving the overall practical performance.

[0036] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hydraulic fracturing test device for a topological structure fractured rock sample, comprising a sealing back plate (1), an observation panel (2) and a hollowed front plate (3), characterized in that, On the inner side of the four corners of one side surface of the sealed backplane (1), prestressed bolts (4) are provided. At the end of one side surface of the prestressed bolts (4), fastening nuts (5) are provided. In the middle of one side surface of the sealed backplane (1), a high-pressure water injection hole (6) is provided. At the other end of one side surface of the prestressed bolts (4), an observation panel (2) is provided. Sealing rings (7) are provided in the middle of the inner side surfaces of the sealed backplane (1) and the observation panel (2). On one side surface of the observation panel (2), a hollow front plate (3) is provided. Inside the four corners of one side surface of the hollow front plate (3), bolt bayonets (8) are provided.

2. The hydraulic fracturing test device for fractured rock samples with a topological structure according to claim 1, characterized in that The sealed backplane (1), the observation panel, and the hollow front plate (3) are connected and fixed by prestressed bolts (4). The heights of the sealed backplane (1) and the hollow front plate (3) are both 140 mm, and the widths are both 175 mm. 17-mm round holes are provided at the four corners of one side surface of the sealed backplane (1).

3. A hydraulic fracturing test device for fractured rock samples with a topological structure according to claim 1, characterized in that, The prestressed bolts (4) and the fastening nuts (5) are in threaded connection. The prestressed bolts (4) are of the external hexagon head high-strength bolts of the 12.9-grade DIN933 / 931 type, with an outer diameter of 16 mm and a length of 130 mm. The sealed backplane (1) and the high-pressure water injection hole (6) are in threaded connection. A bolt connection hole is provided at the center of the sealed backplane (1) corresponding to the high-pressure water injection hole (6). The diameter of the high-pressure water injection hole (6) is 5 mm, and the depth is 10 mm.

4. A hydraulic fracturing test device for fractured rock samples with a topological structure according to claim 1, characterized in that, The sealed backplane (1) and the observation panel (2) are assembled with the sealing ring (7) by splicing. The sealing ring (7) is an O-ring with a rectangular cross-section, made of a black fluororubber layer. The inner rectangle length of the sealing ring (7) is 110 mm, the width is 45 mm, the outer rectangle length is 118 mm, the width is 53 mm, and the thickness is 4 mm.

5. The hydraulic fracturing test device for fractured rock samples with a topological structure according to claim 1, characterized in that, Installation grooves are provided on the inner sides of the sealed backplane (1) and the observation panel (2), and the sealing ring (7) is fixed through the installation grooves. The depth of the installation grooves on the inner sides of the sealed backplane (1) and the observation panel (2) is 2.5 mm, the width is 4 mm, the inner width is 45 mm, the outer width is 53 mm, the inner height is 110 mm, and the outer height is 118 mm.

6. The hydraulic fracturing test device for fractured rock samples with a topological structure according to claim 1, characterized in that, The thickness of the observation panel (2) is 40 mm, and it is composed of a polycarbonate transparent plate. An observation window is provided in the middle of the hollow front plate (3). The observation window adopts a slope design, with a height of 110 mm and a width of 75 mm. The bolt bayonets (8) and the prestressed bolts (4) are correspondingly arranged. The length of the bolt bayonets (8) is 29 mm, the width is 25 mm, and the hollow depth is 10 mm.

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