A measuring system and a measuring method for the fracture occurrence of a borehole wall

Abstract

The application discloses a kind of borehole wall fracture occurrence's measuring system and measuring method, comprising: center tube, when using, one end thereof is communicated with drill rod, the other end is closed, through hole is provided on the pipe wall of center tube;Impression cylinder is sleeved outside center tube and forms sealed space between the two, the sealed space is communicated with center tube by through hole, the impression cylinder includes the rubber tube that meets high pressure water expansion and flexible film pressure sensor wrapped on rubber tube, the flexible film pressure sensor includes pressure contact surface and non-contact surface, the pressure non-contact surface of flexible film pressure sensor is arranged towards center tube, the pressure contact surface of flexible film pressure sensor is arranged away from center tube;Azimuth orientation device is arranged at the end side of impression cylinder;Data acquisition device is connected with flexible film pressure sensor, azimuth orientation device, for acquiring the direction information that flexible film pressure sensor senses pressure data and azimuth orientation device acquires direction information.The application realizes the " visualization " continuous measurement of hole wall fracture, improves the efficiency and accuracy of hydraulic fracturing direction test.

Description

Technical Field

[0001] This invention belongs to the technical field of geological exploration, specifically relating to a measurement system and method for measuring the occurrence of borehole wall fractures. Background Technology

[0002] The hydraulic fracturing stress measurement method is the main in-situ testing method for rock mass stress recommended by the International Society for Rock Mechanics (ISRM), the American Society for Materials Science (ASTM), and relevant domestic regulations and standards. It mainly consists of two parts: stress value and direction testing.

[0003] Currently, the geostress orientation testing mainly utilizes expandable directional impressions with a semi-vulcanized rubber outer layer. During orientation determination, the impression is placed at the test depth, and a pressurization system on the ground expands it, reopening closed fractures in the rock mass. The surface semi-vulcanized rubber is forced into the fracture, and pressure is maintained for a period of time, leaving a raised imprint on the impression surface corresponding to the fracture. The pressure is then released, and the impression is removed to the borehole opening. The raised imprint left by the fracture is examined and traced using transparent film paper. A directional device connected to the impression is used to determine the baseline marker. Finally, based on the relationship between the baseline orientation and the imprint, the attitude information of the tested fracture is calculated, and the orientation of the maximum horizontal principal stress is determined. However, this method requires removing and replacing the impression for each fracture tested, resulting in low testing efficiency and high costs. Furthermore, friction between the impression and the borehole wall during removal can erase the imprint, affecting the determination of the fracture attitude and principal stress orientation. Summary of the Invention

[0004] One objective of this invention is to address the shortcomings of existing technologies by providing a measurement system for borehole wall fracture orientation. This system enables "visualized" continuous measurement of borehole wall fractures, thereby improving the efficiency and accuracy of directional testing using the hydraulic fracturing method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A system for measuring the orientation of borehole wall fractures, comprising:

[0007] The central tube is connected to the drill rod at one end and closed at the other end during use. A through hole is provided on the wall of the central tube.

[0008] An impression cylinder is fitted outside a central tube, forming a sealed space between them. The sealed space is connected to the central tube through a through hole. The impression cylinder includes a rubber tube that expands when exposed to high-pressure water and a flexible thin-film pressure sensor wrapped around the rubber tube. The flexible thin-film pressure sensor includes a pressure contact surface and a non-contact surface. The non-contact surface of the flexible thin-film pressure sensor faces the central tube, and the pressure contact surface of the flexible thin-film pressure sensor faces away from the central tube.

[0009] Orientation device, which is set on the end side of the impression cylinder;

[0010] A data acquisition device, which is connected to a flexible thin-film pressure sensor and an orientation device, is used to acquire pressure data sensed by the flexible thin-film pressure sensor and obtain directional information acquired by the orientation device.

[0011] A data processing device, which is connected to a data acquisition device, is used to receive data acquired by the data acquisition device and process the data.

[0012] Furthermore, a layer of adhesive that expands when exposed to high-pressure water is applied to the outside of the flexible thin-film pressure sensor.

[0013] Furthermore, the thickness of the adhesive layer does not exceed 2mm.

[0014] Furthermore, the two ends of the central tube and the impression cylinder are connected by connectors to seal the space between them, forming the sealed space.

[0015] Furthermore, the orientation device is an electronic compass.

[0016] Furthermore, a sleeve is provided at the end of the impression cylinder away from the drill rod, and the data acquisition device and the orientation device are sealed inside the sleeve.

[0017] Another object of the present invention is to provide a measurement method for a measurement system based on the above-described borehole wall fracture orientation, comprising the following steps:

[0018] Step 1: Connect the central tube to the drill pipe, and then send the measurement system to the crack in the ground stress test section of the borehole;

[0019] Step 2: Inject high-pressure water into the drill pipe. The high-pressure water enters the sealed space through the drill pipe, the central tube, and the through hole on the central tube. Under the action of the high-pressure water in the sealed space, the rubber sleeve expands and adheres tightly to the borehole wall. The data acquisition device automatically records and stores the orientation information on the orientation device and the contact pressure information and force process on the flexible thin film pressure sensor. The data processing device processes the pressure difference information between the intact borehole wall and the fracture on the flexible thin film pressure sensor collected by the data acquisition device to obtain the fracture orientation information.

[0020] Step 3: After the high-pressure water injected into the drill pipe reaches the target pressure value, maintain the pressure for a certain period of time and then release the pressure to complete the fracture occurrence information of the current test section;

[0021] Step 4: Test the fracture orientation of the next test section by increasing or decreasing the length of the drill pipe and repeating the above steps until the orientation measurement of all test sections is completed.

[0022] Furthermore, the data acquisition device is set to start and stop working based on a pressure threshold. That is, when the pressure is greater than the threshold, the data acquisition device will start working, and when the pressure is less than the threshold, the data acquisition device will stop working.

[0023] Furthermore, the target pressure in step 3 is determined based on the tensile pressure measured by the ground stress value, and the target pressure is 1.3 to 1.5 times the tensile pressure.

[0024] Furthermore, in step 3, the pressure is released after holding for 1-3 minutes.

[0025] The principle of the measurement system of this invention is as follows:

[0026] When the impression cylinder expands under the water pressure within the sealed space and re-tensions the crack in the hole wall, the contact pressure on the intact hole wall and the crack on the flexible thin-film pressure sensor is different, such as... Figure 1 As shown; when the water pressure inside the impression cylinder is P At that time, the horizontal force relationship of the micro-segment at the intact hole wall of the flexible thin-film pressure sensor is as follows:

[0027] (1)

[0028] In the formula, P The internal water pressure at a certain moment during the molding process of the impression cylinder. F The contact reaction force of the orifice wall on the pressure contact surface of the flexible thin-film pressure sensor. T 1 represents the circumferential tensile force experienced by the micro-segment of the impression cylinder within the complete hole wall section. θ The angle between the direction of the circumferential tension and the direction of the vertical line of the internal water pressure;

[0029] The pressure contact surface of the flexible thin-film pressure sensor is subjected to contact reaction force from the orifice wall. F :

[0030] (2)

[0031] In flexible thin-film pressure sensors, at the gaps in the orifice wall, the pressure contact surface is not subjected to contact reaction force from the orifice wall. F =0; At this point, the internal water pressure is balanced with the horizontal component of the tangential tension of the impression cylinder, and thus... ,in, T 2 represents the circumferential tensile force exerted on the micro-segment of the impression cylinder in the fissure hole wall section;

[0032] As can be seen from the above, there is a large contact pressure difference between the intact hole wall and the crack in the flexible thin film pressure sensor. Based on this characteristic, the orientation information of the crack can be easily identified.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: The data acquisition device of the present invention can automatically record the orientation on the orientation device and the contact pressure and force process on the flexible thin film pressure sensor, thereby obtaining the pressure distribution map of the hole wall crack during the imprinting process. Since there is a large contact pressure difference between the intact hole wall and the crack on the flexible thin film pressure sensor, the data acquisition device obtains the crack orientation information based on the pressure difference information. Then, based on the relationship between the electronic pressure paper baseline position (generally pointing due north) determined by the electronic compass orientation instrument and the crack, the direction of the maximum horizontal principal stress can be calculated and determined. Therefore, the measurement system of the present invention realizes the full-process electronic information "visual" hole wall crack orientation measurement, clearly displaying the crack orientation in an image, improving the crack morphology identification and direction measurement accuracy. The present invention solves the problems of the prior art requiring frequent removal of the imprinter to check the results and replacement, and the arbitrary erasure of the imprint traces during the extraction process. Instead, it enables rapid and continuous imprinting, greatly reducing the workload of hole wall crack orientation measurement and improving testing efficiency. Attached Figure Description

[0034] Figure 1 This is a schematic diagram illustrating the pressure difference between the complete hole wall and the crack in this invention.

[0035] Figure 2 This is a schematic diagram of a borehole wall fracture orientation measurement system according to an embodiment of the present invention, wherein (a) is a front view, (b) is a cross-sectional view of the dashed part in (a), and (c) is a left view of the dashed part in (a).

[0036] Figure 3 This is a three-dimensional schematic diagram of the measurement system according to an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the electronic module connection in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of the impression result in an embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0041] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0042] Example 1

[0043] like Figure 2 , Figure 3 As shown, this embodiment of the invention discloses a measurement system for the occurrence of borehole wall fractures, including a central tube 1, an impression cylinder 2, an orientation device 3, and a data acquisition device 4. In this embodiment, the diameter of the central tube 1 is smaller than the diameter of the drill rod. During use, one end of the central tube 1 is connected to the drill rod via a transformer 5, while the other end is closed. Furthermore, multiple through holes 11 are provided on the wall of the central tube 1.

[0044] The impression cylinder 2 includes a rubber cylinder 21 that expands under high pressure water and a flexible thin-film pressure sensor 22 wrapped around the rubber cylinder 21. The inner diameter of the rubber cylinder 21 is larger than the outer diameter of the central tube 1. The flexible thin-film pressure sensor 22 includes a pressure contact surface and a non-contact surface. The non-contact surface of the flexible thin-film pressure sensor 22 faces the central tube 1, and the pressure contact surface faces away from the central tube 1. To protect the flexible thin-film pressure sensor 22, a thin rubber layer 23 is covered on it. To prevent the rubber layer from being too thick and affecting the pressure sensitivity of the flexible thin-film pressure sensor 22, the thickness of the rubber layer 23 does not exceed 2 mm. In this embodiment, the thickness of the rubber layer 23 is 1 mm. Both the rubber layer 23 and the rubber cylinder 21 are made of semi-vulcanized rubber. The impression cylinder 2 is sleeved outside the central tube 1. One end of it is connected to the central tube 1 through the upper connector 6, and the other end is connected to the central tube 1 through the lower connector 7. The upper connector 6 and the lower connector 7 seal the space between the rubber cylinder 21 and the central tube 1 to form a sealed space. The sealed space is connected to the central tube 1 through the through hole 11.

[0045] A sleeve 8 is fitted onto the lower connector 7. A power supply 9, a directional device 3, and a data acquisition device 4 are installed inside the sleeve 8. The directional device 3, the flexible thin-film pressure sensor 22, and the data acquisition device 4 are connected to the power supply 9 via a circuit. The power supply 9 is then switched on, supplying power to all three components. Figure 4The sleeve seals the power supply 9, orientation device 3, and data acquisition device 4 inside to prevent them from being damaged by water during operation. Furthermore, the flexible thin-film pressure sensor 22, orientation device 3, and data acquisition device 4 are connected. The data acquisition device 4 collects pressure data sensed by the flexible thin-film pressure sensor 22 and acquires direction information collected by the orientation device 3. After the test, the data acquisition device 4 is connected to a data processing device via a line. The data processing device receives and processes the information collected by the data acquisition device 4. Alternatively, the data acquisition device 4 can be connected to the data processing device during the test, allowing the data processing device to acquire and process the information collected by the data acquisition device 4 in real time. To better collect useful information and prevent the acquisition of unnecessary stress information, the data acquisition device 4 is set to start and stop operation triggered by a pressure threshold. That is, if the pressure is greater than the threshold, the data acquisition device 4 is triggered to start operation; if the pressure is less than the threshold, the data acquisition device 4 is triggered to stop operation. In this embodiment, the pressure threshold can be set to 1 MPa. Data acquisition starts when the contact pressure is greater than this threshold and stops when the pressure is less than this threshold. In this embodiment, the orientation device 3 is an electronic compass, which always points due north, providing a basis for subsequent calculations of the direction of ground stress.

[0046] Example 2

[0047] This embodiment provides a measurement method based on the above-described measurement system for borehole wall fracture orientation, comprising the following steps:

[0048] Step 1: After connecting the central tube 1 to the drill pipe through the adapter 5, send the above-mentioned measurement system to the crack in the ground stress test section in the borehole;

[0049] Step 2: Inject high-pressure water into the drill rod. The high-pressure water enters the sealed space through the drill rod, the central tube 1, and the through hole 11 on the central tube 1. Under the action of the high-pressure water in the sealed space, the rubber sleeve 21 expands and adheres tightly to the borehole wall. When the impression cylinder 2 expands under water pressure and adheres to the borehole wall to re-open the crack, the data acquisition device 4 is triggered by pressure and automatically records and stores the orientation on the orientation device 3 and the contact pressure and force process on the flexible thin film pressure sensor 22. Since there is a large pressure difference between the contact pressure of the flexible thin film pressure sensor 22 with the intact borehole wall and the contact pressure with the crack, after the data acquisition device collects all the pressure information of the flexible thin film pressure sensor 22, the data processing device can obtain the crack orientation information based on the pressure difference information it has collected.

[0050] Step 3: After the high-pressure water injected into the drill pipe reaches the target pressure value, maintain the pressure for a certain period of time, and then release the pressure. During the pressure release process, when the water pressure in the test section is less than the threshold, the data acquisition device 4 stops working due to the pressure, thus completing the measurement of the fracture orientation information of the current test section. In this embodiment, the target pressure is determined based on the magnitude of the tensile pressure measured by the ground stress value, and is generally about 1.3 to 1.5 times the tensile pressure to ensure that the fracture is fully opened. After reaching the current pressure value, maintain the pressure for about 1-3 minutes, and then release the pressure to complete the first test section.

[0051] Step 4: By increasing or decreasing the length of the drill pipe and repeating the above steps, test the fracture orientation of the next test section until all test sections are completed. Remove the impression cylinder to the surface at the borehole opening, open the sleeve 8, switch on the power supply 9, remove the data acquisition device 4, and connect the data acquisition device 4 to the data processing device. In this embodiment, the data processing device is a computer. The dedicated software on the computer displays and processes the video and images to obtain the borehole wall fracture pressure distribution map during the impression process (see...). Figure 5 ), Figure 5 The line formed at the zero pressure point corresponds to the borehole wall fracture. After obtaining the borehole wall fracture, the direction of the maximum horizontal principal stress is calculated based on the positional relationship between the baseline position determined by the electronic compass (generally pointing due north) and the borehole wall fracture.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A system for measuring the orientation of borehole wall fractures, characterized in that, include: The central tube is connected to the drill rod at one end and closed at the other end during use. A through hole is provided on the wall of the central tube. An impression cylinder is fitted outside a central tube, forming a sealed space between them. The sealed space is connected to the central tube through a through hole. The impression cylinder includes a rubber tube that expands when exposed to high-pressure water and a flexible thin-film pressure sensor wrapped around the rubber tube. The flexible thin-film pressure sensor includes a pressure contact surface and a non-contact surface. The non-contact surface of the flexible thin-film pressure sensor faces the central tube, and the pressure contact surface of the flexible thin-film pressure sensor faces away from the central tube. Orientation device, which is set on the end side of the impression cylinder; A data acquisition device, which is connected to a flexible thin-film pressure sensor and an orientation device, is used to acquire pressure data sensed by the flexible thin-film pressure sensor and obtain directional information acquired by the orientation device. A data processing device, which is connected to a data acquisition device, is used to receive data acquired by the data acquisition device and process the data.

2. The measurement system for borehole wall fracture orientation according to claim 1, characterized in that, A layer of adhesive that expands when exposed to high-pressure water is applied to the outside of the flexible thin-film pressure sensor.

3. The measurement system for borehole wall fracture orientation according to claim 2, characterized in that, The thickness of the adhesive layer shall not exceed 2mm.

4. The measurement system for borehole wall fracture orientation according to claim 1, characterized in that, The central tube and the two ends of the impression cylinder are connected by connectors to seal the space between them, forming the sealed space.

5. The measurement system for borehole wall fracture orientation according to claim 1, characterized in that, The orientation device is an electronic compass.

6. The measurement system for borehole wall fracture orientation according to claim 1, characterized in that, A sleeve is installed at the end of the impression cylinder away from the drill rod, and the data acquisition device and the orientation device are sealed inside the sleeve.

7. A measurement method for a borehole wall fracture orientation measurement system, comprising the borehole wall fracture orientation measurement system as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Connect the central tube to the drill pipe, and then send the measurement system to the crack in the ground stress test section of the borehole; Step 2: Inject high-pressure water into the drill pipe. The high-pressure water enters the sealed space through the drill pipe, the central tube, and the through hole on the central tube. Under the action of the high-pressure water in the sealed space, the rubber sleeve expands and adheres tightly to the borehole wall. The data acquisition device automatically records and stores the orientation information on the orientation device and the contact pressure information and force process on the flexible thin film pressure sensor. The data processing device processes the pressure difference information between the intact borehole wall and the fracture on the flexible thin film pressure sensor collected by the data acquisition device to obtain the fracture orientation information. Step 3: After the high-pressure water injected into the drill pipe reaches the target pressure value, maintain the pressure for a certain period of time and then release the pressure to complete the fracture occurrence information of the current test section. Step 4: Test the fracture orientation of the next test section by increasing or decreasing the length of the drill pipe and repeating the above steps until the orientation measurement of all test sections is completed.

8. The measurement method of the borehole wall fracture orientation measurement system according to claim 7, characterized in that, The data acquisition device is set to start and stop working based on a pressure threshold. That is, when the pressure is greater than the threshold, the data acquisition device will start working, and when the pressure is less than the threshold, the data acquisition device will stop working.

9. The measurement method of the borehole wall fracture orientation measurement system according to claim 7, characterized in that, The target pressure in step 3 is determined based on the tensile pressure measured by the ground stress value, and the target pressure is 1.3 to 1.5 times the tensile pressure.

10. The measurement method of the borehole wall fracture orientation measurement system according to claim 7, characterized in that, After holding the pressure for 1-3 minutes in step 3, release the pressure.

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