Boosting device and method suitable for hydraulic fracturing ground stress test

Abstract

The invention discloses a pressure boosting device and method suitable for a hydraulic fracturing ground stress test, the pressure boosting device is sequentially connected with an upper rubber plug and a lower rubber plug of a ground stress test device through a push-pull pressure relief conversion device, the pressure boosting device comprises a pressure boosting cylinder body, a first inner cavity and a second inner cavity, the first inner cavity is connected with a hydraulic device through a hydraulic drill rod, and the second inner cavity is connected with a second hydraulic device through a hydraulic drill rod; the second inner cavity is sequentially connected with the upper rubber plug and the lower rubber plug through a push-pull pressure relief conversion device, an exhaust hole communicated with the first inner cavity is formed in the side wall of the pressure boosting cylinder body, and a water inlet and outlet hole communicated with the second inner cavity is further formed in the side wall of the pressure boosting cylinder body. The low-pressure piston is movably arranged in the first inner cavity, the high-pressure piston is movably arranged in the second inner cavity, and the force transmission column is connected with the low-pressure piston and the high-pressure piston. According to the invention, the limited pressure in the coring drill rod can be increased to the test pressure required by the crustal stress test, so that the equipment loss risk during the crustal stress test is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock mechanics testing, and in particular relates to a pressure boosting device and method suitable for ground stress testing using a hydraulic fracturing method. Background Art

[0002] Hydraulic fracturing is a direct method for measuring geostress. It involves applying high hydraulic pressure to the borehole wall at a predetermined depth, fracturing the wall. By measuring the pressure at a characteristic point during the fracturing process, the geostress in the rock mass near the measuring point is calculated. The fracture direction at that location is then determined, revealing the horizontal principal stress vector at the measuring point.

[0003] Conventional hydraulic fracturing geostress testing is mainly divided into single-tube and dual-tube methods. The single-tube method switches the pressure channel between the packer and the test section by connecting a push-pull valve between the drill pipe and the double-plug packer. It is suitable for continuous and rapid testing in deep boreholes with high water levels (no more than 60m) and is simple to operate. The dual-tube method forms two pressure channels by connecting a slender high-pressure water pipe to the packer and the drill pipe. It is suitable for shallow borehole testing (the borehole depth generally does not exceed 150m and the water level generally does not exceed 60m) and is complex to operate. As underground projects become deeper and deeper, geological boreholes with great burial depths and deep water levels will become common, and the single-tube method is generally used for testing.

[0004] In recent years, with the rapid development of hydraulic exploration technology, more and more ground stress test holes are drilled using rope coring drill pipes, and the drilling depth is getting deeper and deeper. Due to the thin wall of the drill pipe, the core drill pipe wall and threaded connection are easily deformed under high pressure during the ground stress test, which poses a great risk of equipment loss. Summary of the Invention

[0005] One object of the present invention is to address the shortcomings of the existing technology and provide a pressure boosting device suitable for hydraulic fracturing ground stress testing. The device can increase the limited pressure in the coring drill pipe to the test pressure required for ground stress testing, thereby greatly reducing the risk of equipment loss during ground stress testing.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A booster device suitable for hydraulic fracturing ground stress testing, wherein the booster device is sequentially connected to an upper rubber plug and a lower rubber plug of a ground stress testing device via a push-pull pressure relief conversion device, and comprises:

[0008] A booster cylinder body is provided with a first inner cavity and a second inner cavity that are interconnected. The first inner cavity is connected to the hydraulic device through a hydraulic drill rod. The second inner cavity is connected to the upper rubber plug and the lower rubber plug in sequence through a push-pull pressure relief conversion device. An exhaust hole communicating with the first inner cavity is provided on the side wall of the booster cylinder body. An inlet and outlet water hole communicating with the second inner cavity is also provided on the side wall of the booster cylinder body.

[0009] A piston device comprising a low-pressure piston movably disposed in the first inner cavity, a high-pressure piston movably disposed in the second inner cavity, and a force transmission column connecting the low-pressure piston and the high-pressure piston;

[0010] In the initial state, the high-pressure piston is located on one side of the water inlet and outlet holes and is close to the first inner cavity. The low-pressure piston is pressurized by the hydraulic device. The low-pressure piston pushes the high-pressure piston to move and the high-pressure piston passes through the water inlet and outlet holes. At this time, the high-pressure piston is in a sealed state toward the second inner cavity on the side of the push-pull pressure relief device. In this state, pressurization continues to be achieved by switching the passage of the push-pull pressure relief conversion device to pressurize the upper and lower rubber plugs or the test section.

[0011] Furthermore, the inner diameter of the first inner cavity is greater than the inner diameter of the second inner cavity.

[0012] Furthermore, an elastic reset device is mounted on the force transmission column, and the outer diameter of the elastic reset device is larger than the inner diameter of the second inner cavity and not larger than the inner diameter of the first inner cavity.

[0013] Furthermore, the elastic reset device includes a spring.

[0014] Furthermore, the exhaust hole is arranged on the inner wall of the boosting cylinder close to the second inner cavity, and the water inlet and outlet holes are arranged on the inner wall of the boosting cylinder close to the first inner cavity.

[0015] Furthermore, the push-pull pressure relief conversion device is connected to the upper rubber plug and the lower rubber plug through a high-pressure oil pipe. In the initial state, the second inner cavity is connected to the upper rubber plug and the lower rubber plug through the push-pull pressure relief conversion device. The push-pull pressure relief device is moved down a certain distance toward the upper rubber plug to disconnect the passage between the push-pull pressure relief conversion device and the upper and lower rubber plugs.

[0016] Another object of the present invention is to provide a method for pressurizing a test section using the above-mentioned pressure-boosting device, characterized in that it comprises the following steps:

[0017] Step 1: Connect the second inner cavity of the booster device to the upper and lower rubber plugs in sequence through the push-pull pressure relief conversion device, and connect the first inner cavity to the hydraulic device through the hydraulic drill pipe. The number of boosters is determined according to needs, and the boosters are connected in series. Then, all the connected devices are lowered to the position determined for the test in the borehole. In the initial state, the push-pull pressure relief conversion device is in a stretched state, and the water in the borehole is connected to the upper and lower rubber plugs through the water inlet and outlet holes on the booster device and the push-pull pressure relief conversion device;

[0018] Step 2: Apply pressure to the hydraulic drill pipe through the hydraulic device. Under the action of pressure, the low-pressure piston, force transmission column, and high-pressure piston in the boosting device move toward the push-pull pressure relief conversion device. At this time, the air or water between the low-pressure piston and the high-pressure piston is discharged through the exhaust hole. After the high-pressure piston moves through the water inlet and outlet holes, the high-pressure piston is in a sealed state toward the cavity of the push-pull pressure relief conversion device. The piston device is continuously pushed to move. The pressure is transmitted to the upper and lower rubber plugs through the push-pull pressure relief conversion device. The upper and lower rubber plugs are pressurized and expanded to seal in the drill hole.

[0019] Step 3: Continue to lower the hydraulic drill pipe to push the push-pull pressure relief conversion device downward to a preset position. At this time, disconnect the passages between the push-pull pressure relief conversion device and the upper and lower rubber plugs, connect the push-pull pressure relief device to the test section in the borehole, relieve the pressure on the hydraulic drill pipe, and return the piston device to its initial state. At this time, the water in the test section borehole is connected to the test section in the borehole through the water inlet and outlet holes of the booster device and the push-pull pressure relief conversion device;

[0020] Step 4: Apply pressure to the hydraulic drill pipe. At this time, the air or water between the low-pressure piston and the high-pressure piston is discharged through the exhaust hole. After the high-pressure piston moves through the water inlet and outlet holes, the high-pressure piston is sealed toward the second chamber of the push-pull pressure relief conversion device. Continue to apply pressure to the hydraulic drill pipe to pressurize the test section.

[0021] Step 5: After the ground stress test is completed, return the piston device to its initial state; lift the hydraulic drill pipe to lift the push-pull pressure relief conversion device until it is connected to the upper and lower rubber plugs, thereby relieving the pressure on the upper and lower rubber plugs.

[0022] Furthermore, the pressure of the boosting device is determined according to the pressure required during the test section test, and the total number of boosting devices that need to be connected in series is determined according to the pressure and the boosting coefficient of each boosting device.

[0023] Furthermore, the boost coefficient of a single boost device is calculated by the following formula:

[0024]

[0025]

[0026] In the formula: k——boost coefficient;

[0027] k1 - resistance coefficient of the low-pressure piston moving toward the high-pressure piston;

[0028] p1 - pressure in the first inner cavity;

[0029] p2 - pressure in the second inner cavity;

[0030] s1——cross-sectional area of low-pressure piston;

[0031] s2——cross-sectional area of high-pressure piston;

[0032] l1 - the distance traveled by the low-pressure piston during the test;

[0033] Q - the flow rate of fluid injected during the test;

[0034] S is the internal cross-sectional area of the hydraulic drill pipe during the test.

[0035] Compared with existing technologies, the present invention offers the following advantages: While fully utilizing the coring drill pipe, the present invention integrates a pressure-boosting device into a hydraulic fracturing in-situ stress testing device. During in-situ stress testing, the limited pressure in the coring drill pipe can be raised to the required test pressure, significantly reducing the risk of equipment loss during in-situ stress testing. The pressure-boosting device can be used individually or in combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of a single boosting device in use according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the structure of multiple boosting devices in use according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0040] The present invention will be further described below with reference to specific examples, but they are not intended to limit the present invention.

[0041] like Figure 1As shown, an embodiment of the present invention discloses a booster device suitable for hydraulic fracturing geostress testing, comprising a booster cylinder 1 and a piston assembly. A first inner chamber 11 and a second inner chamber 12 are provided within the booster cylinder 1, interconnected. To increase the pressure in the second inner chamber 12, the inner diameter of the second inner chamber 12 is set to be smaller than that of the first inner chamber 11. A vent 13 is provided on the side wall of the booster cylinder 1, communicating with the first inner chamber 11. Water inlet and outlet holes 14 are also provided on the side wall of the booster cylinder 1, communicating with the second inner chamber 12. The vent 13 is provided on the inner wall of the booster cylinder 1 near the second inner chamber 12, and the water inlet and outlet holes 14 are provided on the inner wall of the booster cylinder 1 near the first inner chamber 11. The piston assembly comprises a low-pressure piston 21 movably disposed in the first inner chamber 11, a high-pressure piston 22 movably disposed in the second inner chamber 12, and a force transmission column 23 connecting the low-pressure piston 21 and the high-pressure piston 22. To prevent water or air leakage, a sealing ring is installed between the low-pressure piston 21 and the inner wall of the first inner chamber 11, and between the high-pressure piston 22 and the inner wall of the second inner chamber 12. To facilitate the piston assembly's return to its initial position upon pressure relief, a resilient reset device is mounted on the force transmission post 23. In this embodiment, the resilient reset device is a spring 24. The outer diameter of spring 24 is comparable to the inner diameter of the first inner chamber 11, ensuring that spring 24 remains captive within the first inner chamber 11 when pressure is applied.

[0042] During use, the booster device is connected to the hydraulic fracturing in-situ stress testing device. Specifically, the first inner chamber 11 of the booster device 1 is connected to the hydraulic device via the hydraulic drill pipe 3, which applies pressure to the first inner chamber 11. The second inner chamber 12 of the booster device is connected to the push-pull pressure relief conversion device 5 via a variable joint 4. The inner diameter of the second inner chamber 12 increases near the variable joint 4, and the inner diameter of the end of the variable joint 4 connected to the second inner chamber 12 is larger than the inner diameter of the end of the variable joint 4 connected to the push-pull pressure relief conversion device 5. The push-pull pressure relief conversion device 5 is connected to the upper rubber plug 6 and the lower rubber plug 7 via a high-pressure oil pipe 8. In the initial state, the second inner chamber 12 is connected to the upper rubber plug 6 and the lower rubber plug 7 through the push-pull pressure relief conversion device 5. The push-pull pressure relief conversion device 5 is moved downward a certain distance toward the upper rubber plug 6, disconnecting the push-pull pressure relief conversion device 5 from the upper and lower rubber plugs 6 and 7. At this point, the push-pull pressure relief conversion device 5 is connected to the test section in the borehole.

[0043] In the initial state, the high-pressure piston 22 is located on one side of the water inlet and outlet holes 14 and is close to the first inner cavity 11. The low-pressure piston 21 is pressurized by the hydraulic device. The low-pressure piston 21 pushes the high-pressure piston 22 to move and the high-pressure piston 22 passes through the water inlet and outlet holes 14. At this time, the second inner cavity 12 on the side of the high-pressure piston 12 away from the hydraulic device is in a sealed state; because at this time, the second inner cavity 12 is connected with the upper rubber plug 6 and the lower rubber plug 7 through the push-pull pressure relief conversion device 5, the upper and lower plugs are pressurized and expanded to seal in the borehole.

[0044] The above-mentioned pressure-boosting device is used to pressurize the test section in the borehole, including the following steps:

[0045] The first step is to connect the second inner cavity 12 of the boosting device to the push-pull pressure relief conversion device 5 through the adapter 4, and connect the push-pull pressure relief conversion device 5 to the upper and lower rubber plugs 6 and 7 through the high-pressure oil pipe 8. In this initial state, the second inner cavity 12 is connected to the upper rubber plug 6 and the lower rubber plug 7 through the push-pull pressure relief conversion device 5 and the high-pressure oil pipe 8. The first inner cavity 11 of the boosting device is connected to the hydraulic device through the hydraulic drill pipe 3. After the devices are connected, the hydraulic drill pipe 3 is used to lower the connected devices to the position selected for the test in the borehole. The boosting device can be used individually or in combination. When multiple combinations are used, they are connected in series, see Figure 2 The number of boosting devices is determined according to the needs. Specifically, the pressure of the boosting device is determined according to the pressure required during the test section. Then, the total number of boosting devices required in series is determined based on the pressure and the pressure coefficient of each boosting device. The boost coefficient of a single boosting device can be calculated using the following formula:

[0046]

[0047] In the formula: k——boost coefficient;

[0048] k1——elastic coefficient of spring;

[0049] p1 - pressure in the first inner cavity;

[0050] p2 - pressure in the second inner cavity;

[0051] s1——cross-sectional area of low-pressure piston;

[0052] s2——cross-sectional area of high-pressure piston;

[0053] l1 - the distance traveled by the low-pressure piston during the test;

[0054] Q - the flow rate of fluid injected during the test;

[0055] S——the internal cross-sectional area of the hydraulic drill pipe during the test;

[0056] In the initial state, the push-pull pressure relief conversion device 5 is in a stretched state. At this time, the water in the drilling test section can be connected to the upper and lower rubber plugs 6 and 7 through the water inlet and outlet holes 13 on the booster device, the push-pull pressure relief conversion device 5, and the high-pressure oil pipe 8;

[0057] In the second step, pressure is applied to the hydraulic drill pipe 3 through the hydraulic device. Under the action of pressure, the low-pressure piston 21, the force transmission column 23, and the high-pressure piston 22 in the boosting device move toward the push-pull pressure relief device 5. At this time, the air or water between the low-pressure and high-pressure pistons 21 and 22 is discharged through the exhaust hole 13. During the movement of the high-pressure piston 22, it passes through the water inlet and outlet holes 14. At this time, the second inner cavity 12 on the side of the high-pressure piston 22 facing the push-pull pressure relief device 5 is in a sealed state. At the same time, the upper and lower rubber plugs 6 and 7 expand under the action of high pressure and thus seal the borehole.

[0058] The third step is to lower the hydraulic drill pipe 3 further until the push-pull pressure relief conversion device 5 moves downward in the borehole to the designated test position. At this point, the passages between the push-pull pressure relief conversion device 5 and the upper and lower rubber plugs 6 and 7 are disconnected, and the push-pull pressure relief conversion device 5 is now connected to the test section in the borehole. The pressure applied within the hydraulic drill pipe 3 is released, and the low-pressure piston 21 and high-pressure piston 22 return to their initial positions under the action of the spring 24. The water in the test borehole is then connected to the test section in the borehole through the water inlet and outlet holes 13 of the booster device and the push-pull pressure relief conversion device 5.

[0059] In the fourth step, pressure is applied to the hydraulic drill pipe 3. The low-pressure piston 21, the force transmission column 23, and the high-pressure piston 22 in the boosting device move downward under the action of the pressure. At this time, the air or water between the low-pressure piston 21 and the high-pressure piston 22 is discharged through the exhaust hole 14. The high-pressure piston 22 passes through the water inlet and outlet holes 14 during its movement. At this time, the second inner cavity 12 on the side of the high-pressure piston 22 facing the push-pull pressure relief device 5 is in a sealed state, so that the test section can be pressurized to the specified pressure.

[0060] Step 5: After the ground stress test is completed, the pressure in the hydraulic drill pipe 3 is released. The low-pressure piston 21 and the high-pressure piston 22 return to their initial positions under the action of the spring. The hydraulic drill pipe 3 is lifted to drive the push-pull pressure relief conversion device 5 to be raised until the push-pull pressure relief conversion device 5 is connected to the upper and lower rubber plugs 6 and 7, thereby releasing the pressure in the upper and lower rubber plugs 6 and 7.

[0061] Step 6: After the pressure in the upper and lower rubber plugs 6 and 7 is completely released, the hydraulic drill rod is lifted or increased to the next selected test position and the above operation is repeated.

[0062] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the present invention specification should be included in the protection scope of the present invention.

Claims

1. A booster device suitable for hydraulic fracturing ground stress testing, characterized in that: The boosting device is connected in sequence with the upper rubber plug and the lower rubber plug of the ground stress testing device through the push-pull pressure relief conversion device, and comprises: A booster cylinder body is provided with a first inner cavity and a second inner cavity that are interconnected. The first inner cavity is connected to the hydraulic device through a hydraulic drill rod. The second inner cavity is connected to the upper rubber plug and the lower rubber plug in sequence through a push-pull pressure relief conversion device. An exhaust hole communicating with the first inner cavity is provided on the side wall of the booster cylinder body. An inlet and outlet water hole communicating with the second inner cavity is also provided on the side wall of the booster cylinder body. A piston device comprising a low-pressure piston movably disposed in the first inner cavity, a high-pressure piston movably disposed in the second inner cavity, and a force transmission column connecting the low-pressure piston and the high-pressure piston; In the initial state, the high-pressure piston is located on one side of the water inlet and outlet holes and is close to the first inner cavity. The low-pressure piston is pressurized by the hydraulic device. The low-pressure piston pushes the high-pressure piston to move and the high-pressure piston passes through the water inlet and outlet holes. At this time, the high-pressure piston is in a sealed state toward the second inner cavity on the side of the push-pull pressure relief device. In this state, pressurization continues to be achieved by switching the passage of the push-pull pressure relief conversion device to pressurize the upper and lower rubber plugs or the test section.

2. The booster device for hydraulic fracturing ground stress testing according to claim 1, characterized in that: The inner diameter of the first inner cavity is greater than the inner diameter of the second inner cavity.

3. The booster device suitable for hydraulic fracturing ground stress testing according to claim 2, characterized in that: An elastic reset device is sleeved on the force transmission column, and the outer diameter of the elastic reset device is larger than the inner diameter of the second inner cavity and not larger than the inner diameter of the first inner cavity.

4. The booster device for hydraulic fracturing ground stress testing according to claim 3, characterized in that: The elastic reset device includes a spring.

5. The booster device for hydraulic fracturing ground stress testing according to claim 1, characterized in that: The exhaust hole is arranged on the inner wall of the boosting cylinder body close to the second inner cavity, and the water inlet and outlet holes are arranged on the inner wall of the boosting cylinder body close to the first inner cavity.

6. The booster device for hydraulic fracturing ground stress testing according to claim 1, characterized in that: The push-pull pressure relief conversion device is connected to the upper rubber plug and the lower rubber plug through a high-pressure oil pipe. In the initial state, the second inner cavity is connected to the upper rubber plug and the lower rubber plug through the push-pull pressure relief conversion device. The push-pull pressure relief conversion device is moved down a certain distance toward the upper rubber plug to disconnect the passage between the push-pull pressure relief conversion device and the upper and lower rubber plugs.

7. A method for pressurizing a test section using the boosting device according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Connect the second inner cavity of the booster device to the upper and lower rubber plugs in sequence through the push-pull pressure relief conversion device, and connect the first inner cavity to the hydraulic device through the hydraulic drill pipe. The number of boosters is determined according to needs, and the boosters are connected in series. Then, all the connected devices are lowered to the position determined for the test in the borehole. In the initial state, the push-pull pressure relief conversion device is in a stretched state, and the water in the borehole is connected to the upper and lower rubber plugs through the water inlet and outlet holes on the booster device and the push-pull pressure relief conversion device; Step 2: Apply pressure to the hydraulic drill pipe through the hydraulic device. Under the action of pressure, the low-pressure piston, force transmission column, and high-pressure piston in the boosting device move toward the push-pull pressure relief conversion device. At this time, the air or water between the low-pressure piston and the high-pressure piston is discharged through the exhaust hole. After the high-pressure piston moves through the water inlet and outlet holes, the high-pressure piston is in a sealed state toward the cavity of the push-pull pressure relief conversion device. The piston device is continuously pushed to move. The pressure is transmitted to the upper and lower rubber plugs through the push-pull pressure relief conversion device. The upper and lower rubber plugs are pressurized and expanded to seal in the drill hole. Step 3: Continue lowering the hydraulic drill pipe to push the push-pull pressure relief conversion device downward to a preset position. At this time, disconnect the passage between the push-pull pressure relief conversion device and the upper and lower rubber plugs, relieve the pressure on the hydraulic drill pipe, and return the piston device to its initial state. At this time, the water in the test section borehole is connected to the test section in the borehole through the water inlet and outlet holes of the booster device and the push-pull pressure relief conversion device; Step 4: Apply pressure to the hydraulic drill pipe. At this time, the air or water between the low-pressure piston and the high-pressure piston is discharged through the exhaust hole. After the high-pressure piston moves through the water inlet and outlet holes, the high-pressure piston is sealed toward the second chamber of the push-pull pressure relief conversion device. Continue to apply pressure to the hydraulic drill pipe to pressurize the test section. Step 5: After the ground stress test is completed, return the piston device to its initial state; lift the hydraulic drill pipe to lift the push-pull pressure relief conversion device until it is connected to the upper and lower rubber plugs, thereby relieving the pressure on the upper and lower rubber plugs.

8. The method for pressurizing a test section using a pressure boosting device according to claim 7, characterized in that: The pressure of the boosting device is determined according to the pressure required during the test section test, and the total number of boosting devices that need to be connected in series is determined according to the pressure and the boost coefficient of each boosting device.

9. The method for pressurizing a test section using a pressure boosting device according to claim 8, characterized in that: The boost coefficient of a single boost device is calculated using the following formula: In the formula: k——boost coefficient; k1 - resistance coefficient of the low-pressure piston moving toward the high-pressure piston; p1 - pressure in the first inner cavity; p2 - pressure in the second inner cavity; s1——cross-sectional area of low-pressure piston; s2——cross-sectional area of high-pressure piston; l1 - the distance traveled by the low-pressure piston during the test; Q - the flow rate of fluid injected during the test; S is the internal cross-sectional area of the hydraulic drill pipe during the test.

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