A multi-point crack monitoring device for ground stress testing by hydraulic fracturing

Abstract

The present application discloses a multi-point crack monitoring device for geostress testing by hydraulic fracturing, comprising an upper packer, a fracturing section, and a lower packer coaxially connected in sequence, a camera module with an outer diameter larger than that of the fracturing section being fixed at both ends of the fracturing section, at least three cameras being coaxially arranged on one side of the camera module facing the water outlet in the middle of the fracturing section, a fill light being arranged between the cameras, and a storage unit connected to the control unit signal and a built-in power supply unit being arranged in the camera module. The present application sets up camera modules with multiple cameras and fill lights at both ends of the fracturing section, which can intuitively record the process, direction, and position of rock wall cracks throughout the entire process without blind spots, avoiding the tedious alternating operation of fracturing and impression in impression testing, realizing the synchronization of fracturing test and crack observation, not only significantly improving the efficiency of crack detection, but also improving the accuracy of crack location, with the characteristics of reliable structure, simple operation, and high test efficiency.

Description

Technical Field

[0001] The present application belongs to the field of geological exploration technology, and specifically relates to a multi-point crack monitoring device for hydraulic fracturing ground stress testing, which has reliable structure, simple operation, accurate crack positioning, and high testing efficiency. Background Art

[0002] The geostress problem is the main geological problem faced by underground engineering. During the survey and design stage of large-scale underground engineering projects such as mining projects and transportation tunnel projects, the magnitude of geostress and the direction of principal stress are important considerations in engineering design, and their results directly affect the spatial layout of underground projects.

[0003] For underground projects whose surrounding rock has not yet been exposed, hydraulic fracturing is a relatively common testing method. Through deep-hole geostress testing, the spatial variation characteristics of geostress can be preliminarily identified, and the stability of rock bursts in underground projects and regional geological structures can be judged. Hydraulic fracturing mainly relies on drilling rigs to assist in completing geostress testing in boreholes.

[0004] At present, the hydraulic fracturing test technology is relatively mature and has been widely used in ultra-deep mines and deep tunnel projects. The conventional test method is to lift the fracturing section after the fracturing test and then place the stamper to the test depth, apply a certain pressure to the stamper to make it expand, open the closed cracks in the rock again, and leave marks on the surface of the stamper, then take it out, find the crack indentation on the surface of the stamper to determine the orientation; but during the test, the fracturing section and the stamper need to be lifted and pressurized alternately, resulting in low test efficiency. For this reason, there is also a stamper integrated behind the fracturing section, and then a control valve is set to control different water injection channels, so that each measuring point can be printed once "drill rod lowering-drill rod water injection-stamping-drill rod lifting" operation, so as to complete the fracturing and stamping process, avoid the time spent on repeated lifting-lowering, and thus improve the efficiency of the test; but in the case of drilling more than a kilometer and multiple measuring points, it will still greatly increase the test time and manpower and energy costs, seriously affecting the efficiency of the ground stress test. In addition, since the surface of the impression device is easily scratched by the borehole wall in actual use, it is difficult to accurately distinguish between the crack indentation and scratches on the rock mass. Therefore, there is currently a method of placing the drilling camera equipment to the test depth after the fracturing test, visually finding the location of the cracks on the rock wall and determining the direction with a compass; but this also requires alternating lifting and lowering of the fracturing section and the drilling camera equipment, which is particularly inefficient for testing over a kilometer of borehole and multiple measuring points.

[0005] In the prior art, in order to solve the problems existing in the above-mentioned technology, an axial guide mechanism is provided in the fracturing section, and an axial and circumferential driving mechanism is provided in combination, so that the camera provided in the fracturing section can move axially and circumferentially as needed, so that the cracks in the hydraulic fracturing ground stress test can be comprehensively observed, and the fracturing test and crack observation can be carried out simultaneously, which not only improves the accuracy of crack positioning, but also improves the working efficiency of the test. However, since the borehole diameter of the conventional hydraulic fracturing method is only 76cm, and a high-pressure water channel needs to be provided inside the fracturing section and the wall thickness needs to be ensured to be of sufficient strength, the remaining space for arranging the aforementioned multiple mechanisms is relatively narrow and limited, resulting in the structural strength of each complex mechanism being difficult to ensure good reliability under high-pressure environments. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present application provides a multi-point crack monitoring device for hydraulic fracturing ground stress testing, which has a reliable structure, simple operation, accurate crack positioning, and high testing efficiency.

[0007] The present application is implemented as follows: it includes an upper packer, a fracturing section, and a lower packer coaxially connected in sequence, camera modules are fixedly arranged at both ends of the fracturing section, the outer diameter of the camera module is larger than the outer diameter of the fracturing section, at least three cameras are coaxially distributed on one side of the camera module facing the water outlet in the middle of the fracturing section, a fill light is also arranged between the cameras, a control unit connected to the camera signals, a storage unit connected to the control unit signals, and a power supply unit is also arranged in the camera module.

[0008] Beneficial effects of this application:

[0009] 1. The present application sets a camera module with at least 3 cameras and fill lights evenly distributed at both ends of the fracturing section, so that the process, direction and position of rock wall cracks can be recorded simultaneously and intuitively throughout the whole process without blind spots during fracturing, avoiding the repeated lifting-lowering in conventional tests and the cumbersome operation of "drill rod lowering-drill rod water injection-mold-drill rod lifting" for each measuring point in the improved method, and also solves the problem that the crack indentation and scratch on the mold are difficult to accurately distinguish, which not only significantly improves the efficiency of crack detection, but also improves the accuracy of crack positioning, and the simultaneous realization of fracturing and observation also simplifies the operation process of the entire test.

[0010] 2. The camera module of the present application is fixedly arranged at both ends of the fracturing section, and multiple cameras and fill lights are evenly distributed on the camera module. Therefore, there is no need to move the camera module to conduct a comprehensive observation of the borehole wall around the fracturing section. Moreover, the present application does not have a complicated driving and guiding mechanism. Therefore, it is only necessary to use conventional reinforcing ribs and other structural optimization measures inside the shell to meet the structural strength requirements in a high-pressure use environment, thereby ensuring its good reliability.

[0011] 3. This application adopts an independent modular camera module, which is convenient for adding to the conventional hydraulic fracturing ground stress test device to achieve functional expansion as needed, and is also convenient for upgrading and daily maintenance. In addition, the camera module adopts a cylindrical structure, which can effectively increase the internal space of the camera module, thereby facilitating the layout of the camera, fill light and control circuit, as well as facilitating the layout of additional electronic compass circuits and cleaning nozzles and other functions.

[0012] 4. The present application further sets a pressure sensor and a flow meter connected to the fracturing water channel in the camera module on one side of the upper packer or in the fracturing section. Compared with conventional uphole pressure sensors and flow detection, the influence of pipeline parameters, flow curves, packer and borehole deformation, measuring point depth, etc. can be avoided, and more realistic in-situ stress information can be obtained. Combined with the image data collected by the camera module, it is conducive to a more reasonable and accurate evaluation of the fracturing effect.

[0013] In summary, the present application has the characteristics of reliable structure, simple operation, accurate crack positioning and high testing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is one of the structural diagrams of this application;

[0015] Figure 2 This is the second structural diagram of this application;

[0016] Figure 3 for Figure 1 Sectional view;

[0017] Figure 4 for Figure 2 Schematic diagram of the three-dimensional structure;

[0018] Figure 5 This is a schematic diagram of the control principle of this application;

[0019] In the figure: 1-upper packer, 2-fracturing section, 3-lower packer, 4-camera module, 401-connecting screw hole, 402-connecting shaft, 403-conical surface, 404-cleaning nozzle, 5-camera, 6-fill light, 7-water outlet, 8-fracturing water channel, 9-water hole, 10-step shaft. DETAILED DESCRIPTION

[0020] The present application is further described below in conjunction with the accompanying drawings and embodiments, but the present application is not limited in any way. Any changes or improvements made based on the teachings of the present application belong to the protection scope of the present application.

[0021] like Figures 1 to 5 As shown, the present application includes an upper packer 1, a fracturing section 2, and a lower packer 3 which are coaxially connected in sequence, and camera modules 4 are fixedly arranged at both ends of the fracturing section 2, and an annular plane or conical surface is arranged on the side of the camera module 4 facing the water outlet in the middle of the fracturing section 2, and at least three cameras 5 are coaxially evenly distributed on the annular plane or conical surface of the camera module 4, and a fill light 6 is also arranged between the cameras 5. A control unit connected to the signals of each camera 5 and a storage unit connected to the signals of the control unit are arranged in the camera module 4, and a power supply unit is also arranged in the camera module 4.

[0022] like Figure 1 and 3 As shown, the camera module 4 is an annular structure with an outer diameter not greater than the diameter of the upper packer 1, and the camera module 4 is fixedly connected to the fracturing section 2, or is fixedly connected to the corresponding upper packer 1 and lower packer 3 (not shown in the figure); or step shafts are respectively provided at both ends of the fracturing section 2, and the camera module 4 is sleeved on the step shaft of the fracturing section 2, and the two ends are respectively abutted against the step surface of the step shaft and the corresponding end faces of the packer 1 and lower packer 3.

[0023] like Figure 2 and 4 As shown, the camera module 4 is a cylindrical structure with an outer diameter not greater than the diameter of the upper packer 1. One end of the camera module 4 is fixedly connected to the fracturing section 2 and the other end is fixedly connected to the corresponding upper packer 1 and lower packer 3. A water hole connected to the fracturing water channel of the fracturing section 2 is also provided in the camera module 4.

[0024] One end of the close-up camera 5 of the camera module 4 is provided with a connecting screw hole 401 threadedly connected to the fracturing section 2 , and the other end is provided with a connecting shaft 402 threadedly connected to the corresponding upper packer 1 and lower packer 3 .

[0025] A conical surface 403 is provided on the side of the camera module 4 facing the water outlet in the middle of the fracturing section 2, and the camera 5 and the fill light 6 are fixedly arranged on the conical surface 403. A plurality of cleaning nozzles 404 with openings facing the camera 5 and / or the fill light 6 are coaxially distributed on one side of the conical surface 403 near the water outlet in the middle of the fracturing section 2, and the cleaning nozzles 404 are connected to the water hole.

[0026] The cameras 5 on the camera modules 4 at both ends of the fracturing section 2 are vertically symmetrically arranged or staggered.

[0027] An electronic compass based on a magnetoresistive sensor is also provided on the circuit board in the camera module 4. The electronic compass is any existing circuit based on a magnetoresistive sensor that can realize the function of an electronic compass.

[0028] The camera 5 on the camera module 4 is tilted outwardly and points to one side of the water outlet hole in the middle of the fracturing section 2 .

[0029] The camera module 4 is an ultra-wide-angle camera, and the fill light 6 is a white light LED lamp or a yellow light LED lamp.

[0030] A pressure sensor and a flow meter connected to the fracturing water channel are arranged in the camera module 4 on one side of the upper packer 1 or in the fracturing section 2 .

[0031] The water inlet of the pressure sensor is communicated with the fracturing water channel, and the flow meter is connected in series to the fracturing water channel; the pressure sensor and the flow meter are any existing sensors.

[0032] The power supply unit in the camera module 4 is a battery pack including a rechargeable battery and a control circuit thereof.

[0033] The control unit is any current camera controller, and the storage unit is a current memory card or storage module.

[0034] Working principle and process of this application:

[0035] like Figures 1 to 5 As shown, during the hydraulic fracturing method geostress test, the camera module 4 is sleeved on the step shafts at both ends of the fracturing section 2 and rotated and pressed (as shown in FIG. Figure 1 As shown), or one end of the camera module 4 is threadedly connected to the fracturing section 2 and the other end is threadedly connected to the corresponding upper packer 1 and lower packer 3 (as shown Figure 2As shown), then the drill pipe is placed into the test borehole along with the fracturing section 2, and the position of the fracturing rock formation is determined according to the borehole column chart of the previous geological survey. After the position of the fracturing rock formation is determined, water is injected into the upper packer 1 and the lower packer 3 respectively to seal the fracturing rock formation section; then high-pressure water is injected into the closed space from the outlet hole of the fracturing section 2 to apply pressure to the rock mass in the closed space, and the pressure is continuously increased until the pressure value of the pressure sensor is monitored to drop. At this time, cracks have been generated in the rock mass, causing water to flow in and cause the pressure to drop. During the continuous pressurization process, the power supply unit in the camera module 4 supplies power to each camera 5, the fill light 6 and each unit in the camera module 4, and can also supply power to the pressure sensor and the flow meter when necessary. Each camera 5 on the camera module 4 intuitively records the process, direction and position of the rock wall cracks throughout the process without blind spots, and then saves them in the storage unit after being processed by the control module. An electronic compass can also be set in the camera module 4 to synchronously record the precise position of each camera 5 and the video data in the storage unit, and the data collected by the pressure sensor and the flow meter can also be synchronously stored in the storage unit of the camera module 4. After the fracturing experiment is completed, the image data in the storage unit of the camera module 4, the camera position data, and the data collected by the pressure sensor and the flow meter can be read to accurately determine the principal stress position of the rock mass. Figure 2 and 4 As shown, while the fracturing stage 2 injects high-pressure water into the closed space, the high-pressure water can clean the lens of the camera 5 through the cleaning nozzle 404. If necessary, a corresponding cleaning nozzle 404 can also be set to clean the fill light 6.

[0036] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A multi-point fracture monitoring device for hydraulic fracturing ground stress testing, comprising an upper packer (1), a fracturing section (2), and a lower packer (3) coaxially connected in sequence, characterized in that Camera modules (4) are fixedly arranged at both ends of the fracturing section (2), a conical surface (403) is arranged on the side of the camera module (4) facing the water outlet in the middle of the fracturing section (2), at least three cameras (5) are coaxially evenly distributed on the conical surface (403) of the camera module (4), a fill light (6) is also arranged between the cameras (5), a control unit connected to the signals of each camera (5) and a storage unit connected to the signals of the control unit are arranged in the camera module (4), and a power supply unit is also arranged in the camera module (4); An electronic compass based on a magnetoresistive sensor is also provided on the circuit board in the camera module (4); A pressure sensor and a flow meter connected to the fracturing water channel are arranged in the camera module (4) on one side of the upper packer (1) or in the fracturing section (2); The camera module (4) is a cylindrical structure with an outer diameter no greater than the diameter of the upper packer (1); one end of the camera module (4) is fixedly connected to the fracturing section (2) and the other end is fixedly connected to the corresponding upper packer (1) and lower packer (3); a water hole communicating with the fracturing water channel of the fracturing section (2) is also provided in the camera module (4); A connection screw hole (401) threadedly connected to the fracturing section (2) is provided at one end of the close-up camera (5) of the camera module (4), and a connection shaft (402) threadedly connected to the corresponding upper packer (1) and lower packer (3) is provided at the other end; A plurality of cleaning nozzles (404) with openings facing the camera (5) and / or the fill light (6) are coaxially distributed on one side of the conical surface (403) near the water outlet hole in the middle of the fracturing section (2), and the cleaning nozzles (404) are connected to the water outlet hole.

2. The multi-point crack monitoring device for hydraulic fracturing ground stress testing according to claim 1, characterized in that The camera (5) on the camera module (4) is tilted outwardly and points toward one side of the water outlet hole in the middle of the fracturing section (2).

3. The multi-point crack monitoring device for hydraulic fracturing ground stress testing according to claim 1, characterized in that The camera module (4) is an ultra-wide-angle camera, and the fill light (6) is a white light LED light or a yellow light LED light.

4. The multi-point crack monitoring device for hydraulic fracturing ground stress testing according to claim 1, characterized in that The cameras (5) on the camera modules (4) at both ends of the fracturing section (2) are arranged symmetrically or staggered in the vertical direction.

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