Boosting device suitable for hydraulic fracturing ground stress test

Abstract

The utility model discloses a pressure boosting device suitable for a hydraulic fracturing crustal stress test, which is sequentially connected with an upper rubber plug and a lower rubber plug of a crustal stress test device through a push-pull pressure relief conversion device, and comprises a pressure boosting cylinder body, a first pressure relief device, a second pressure relief device and a pressure relief device, 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 utility model, 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 application belongs to the technical field of rock mass mechanics test, and particularly relates to a pressure boosting device suitable for hydrofracturing method in-situ stress test. BACKGROUND

[0002] The hydrofracturing method is a direct in-situ stress test method. It is to apply high hydraulic pressure to the borehole wall at a designed depth and to fracture the borehole wall, so as to calculate the in-situ stress of the rock mass near the test point by measuring the pressure at the characteristic point in the fracturing process. Then, the fracture direction of the part is determined, so as to obtain the horizontal principal stress vector at the test point.

[0003] The conventional hydrofracturing method in-situ stress test is mainly divided into single pipe method and double pipe method. The single pipe method realizes the pressure channel switching of the packer and the test section by connecting a push-pull valve between the drill pipe and the double-seal packer, is suitable for high water level (not more than 60m) deep borehole continuous rapid test, and is simple in operation. The double pipe method forms two pressure channels by connecting an elongated high-pressure water pipe outside the packer and the drill pipe, is suitable for shallow borehole (the borehole depth is generally not more than 150m, and the water level is generally not more than 60m) test, and is complex in operation. With the increasing depth of underground engineering, deep buried geology boreholes will be widespread, and the single pipe method is generally selected for test.

[0004] In recent years, with the rapid development of hydraulic exploration technology, the in-situ stress test boreholes drilled by using the core drill pipe are more and more, and the borehole depth is more and more large. Since the wall of the core drill pipe is thin, the wall of the core drill pipe and the threaded connection are deformed under high pressure during the in-situ stress test, and there is a great risk of equipment loss. CONTENT OF THE UTILITY MODEL

[0005] The utility model aims at the deficiencies of the prior art, and provides a pressure boosting device suitable for hydrofracturing method in-situ stress test. The device can boost the limited pressure in the core drill pipe to the test pressure required during the in-situ stress test, so as to greatly reduce the risk of equipment loss during the in-situ stress test.

[0006] To solve the above technical problems, the utility model adopts the following technical scheme:

[0007] A pressure boosting device suitable for hydrofracturing method in-situ stress test, the pressure boosting device is sequentially connected with the upper rubber plug and the lower rubber plug of the in-situ stress test device through a push-pull pressure relief conversion device, and comprises:

[0008] A booster cylinder is provided with a first inner cavity and a second inner cavity which are communicated with each other, the first inner cavity is connected with the hydraulic device through the hydraulic drill rod, the second inner cavity is connected with the upper rubber plug and the lower rubber plug through the push-pull pressure relief conversion device in sequence, the exhaust hole which is communicated with the first inner cavity is arranged on the sidewall of the booster cylinder, and the water inlet and outlet hole which is communicated with the second inner cavity is also arranged on the sidewall of the booster cylinder;

[0009] A piston device comprises a low-pressure piston which is movably arranged in the first inner cavity, a high-pressure piston which is movably arranged in the second inner cavity, and a force transmission column which connects 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 hole and is close to the first inner cavity, the low-pressure piston is pressed 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 hole, at this time, the high-pressure piston is in the sealing state towards the second inner cavity on one side of the push-pull pressure relief device, in this state, the pressure is continuously increased, and the passage of the push-pull pressure relief conversion device is switched to realize the pressure increase on the upper and lower rubber plugs or the test section.

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

[0012] Further, the elastic reset device is sleeved on the force transmission column, the outer diameter of the elastic reset device is greater than the inner diameter of the second inner cavity and is not greater than the inner diameter of the first inner cavity.

[0013] Further, the elastic reset device comprises a spring.

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

[0015] Further, the push-pull pressure relief conversion device is connected with the upper rubber plug and the lower rubber plug through the high-pressure oil pipe, in the initial state, the second inner cavity is communicated with 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 downwards by a certain distance towards the direction of the upper rubber plug, and the passage of the push-pull pressure relief conversion device and the upper and lower rubber plugs is disconnected.

[0016] Compared with the prior art, the booster device is connected into the water pressure cracking method ground stress testing device under the premise of fully utilizing the coring drill rod, when the ground stress is tested, the limited pressure in the coring drill rod can be increased to the test pressure required when the ground stress is tested, so that the risk of equipment loss when the ground stress is tested is greatly reduced, and the booster device can be used individually or in combination. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structure schematic view of the single booster device of the utility model embodiment in use.

[0018] Figure 2 This is a schematic diagram of the structure of multiple boosting devices in use according to embodiments of this utility model. Detailed Implementation

[0019] The technical solutions 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 protection scope of the present invention.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0021] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the present invention.

[0022] like Figure 1 As shown, this utility model discloses a pressure boosting device suitable for hydrostatic fracturing in-situ stress testing, including a pressure boosting cylinder 1 and a piston device. A first inner cavity 11 and a second inner cavity 12 are provided within the pressure boosting cylinder 1, communicating with each other. To increase the pressure in the second inner cavity 12, the inner diameter of the second inner cavity 12 is set to be smaller than the inner diameter of the first inner cavity 11. An exhaust port 13 communicating with the first inner cavity 11 is provided on the side wall of the pressure boosting cylinder 1, and an inlet / outlet port 14 communicating with the second inner cavity 12 is also provided on the side wall of the pressure boosting cylinder 1. The exhaust port 13 is located on the inner wall of the pressure boosting cylinder 1 near the second inner cavity 12, and the inlet / outlet port 14 is located on the inner wall of the pressure boosting cylinder 1 near the first inner cavity 11. The piston device includes a low-pressure piston 21 movably disposed in the first inner cavity 11, a high-pressure piston 22 movably disposed in the second inner cavity 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 provided between the low-pressure piston 21 and the inner wall of the first inner cavity 11, and a sealing ring is also provided between the high-pressure piston 22 and the inner wall of the second inner cavity 12. To facilitate the piston assembly returning to its initial position when pressure is released, an elastic reset device is fitted on the force transmission column 23. In this embodiment, the elastic reset device is a spring 24. The outer diameter of the spring 24 is approximately equal to the inner diameter of the first inner cavity 11, so that the spring 24 is always confined within the first inner cavity 11 when pressure is applied.

[0023] In use, the pressure boosting device is connected with the water pressure fracturing method ground stress testing device. Specifically, the first inner cavity 11 of the pressure boosting device 1 is connected with the hydraulic device through the hydraulic drill rod 3, and the hydraulic device applies pressure to the first inner cavity 11 through the hydraulic drill rod 3. The second inner cavity 12 of the pressure boosting device is connected with the push-pull pressure relief conversion device 5 through the variable joint 4, the inner diameter of the second inner cavity 12 near the end of the variable joint 4 is increased, and the inner diameter of the end of the second inner cavity 12 connected with the variable joint 4 is greater than the inner diameter of the end of the variable joint 4 connected with the push-pull pressure relief conversion device 5. The push-pull pressure relief conversion device 5 is connected with the upper rubber plug 6 and the lower rubber plug 7 through the high-pressure oil pipe 8. In the initial state, the second inner cavity 12 is communicated with 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 by a certain distance in the direction of the upper rubber plug 6, and the passage of the push-pull pressure relief conversion device 5 and the upper and lower rubber plugs 6 and 7 is disconnected. At this time, the push-pull pressure relief conversion device 5 is communicated with the test section in the borehole.

[0024] In the initial state, the high-pressure piston 22 is located on one side of the water inlet and outlet hole 14 and is close to the first inner cavity 11. The low-pressure piston 21 is pressed by the hydraulic device, and 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 hole 14. At this time, the second inner cavity 12 on the side away from the hydraulic device of the high-pressure piston 12 is in a sealed state. At this time, the second inner cavity 12 is communicated with the upper rubber plug 6 and the lower rubber plug 7 through the push-pull pressure relief conversion device 5, and the upper and lower rubber plugs are pressurized and expanded to seal in the borehole.

[0025] The test section in the borehole is pressurized by using the pressure boosting device, including the following steps:

[0026] Firstly, the second inner cavity 12 of the pressure boosting device is connected with the push-pull pressure relief conversion device 5 through the variable joint 4, and the push-pull pressure relief conversion device 5 is communicated with 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 communicated with 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 pressure boosting device is connected with the hydraulic device through the hydraulic drill rod 3. After the devices are all connected, the connected devices are lowered to the selected position in the borehole by using the hydraulic drill rod 3. The pressure boosting device can be used individually or in combination. When used in combination, the pressure boosting devices are connected in series. See Figure 2 The number of pressure boosting devices is determined according to the required pressure during the test of the test section, the pressure boosting size of the pressure boosting device, and the total number of pressure boosting devices required for series connection according to the pressure boosting size and the pressure boosting coefficient of each pressure boosting device. The pressure boosting coefficient of a single pressure boosting device can be calculated by the following formula:

[0027]

[0028] In the formula: k is the pressure boosting coefficient.

[0029] k1 - spring constant;

[0030] p1 - pressure in the first inner chamber;

[0031] p2 - pressure in the second inner chamber;

[0032] s1 - cross-sectional area of the low-pressure piston;

[0033] s2 - cross-sectional area of the high-pressure piston;

[0034] l1 - distance travelled by the low-pressure piston during the test;

[0035] Q - fluid flow rate injected during the test;

[0036] S - inner cross-sectional area of the hydraulic drill pipe during the test;

[0037] In the initial state, the push-pull pressure relief conversion device 5 is in the stretched state, at this time, the water in the drilling test section can be communicated through the water inlet and outlet hole 13 on the pressure booster device, the push-pull pressure relief conversion device 5, the high-pressure oil pipe 8 and the upper and lower rubber plugs 6, 7;

[0038] In the second step, the hydraulic device is used to apply pressure to the hydraulic drill pipe 3, the low-pressure piston 21, the force transmission column 23 and the high-pressure piston 22 in the pressure booster device move towards the push-pull pressure relief conversion device 5 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 13, the high-pressure piston 22 moves through the water inlet and outlet hole 14, at this time, the second inner chamber 12 on the side of the push-pull pressure relief conversion device 5 is in a sealed state, and the upper and lower rubber plugs 6, 7 are expanded under the action of high pressure to seal in the drilling hole;

[0039] In the third step, the hydraulic drill pipe 3 is further lowered by a certain distance to the push-pull pressure relief conversion device 5, which moves downward in the drilling hole to the specified position of the test, at this time, the passage of the push-pull pressure relief conversion device 5 and the upper and lower rubber plugs 6, 7 is disconnected, at this time, the push-pull pressure relief conversion device 5 is communicated with the test section in the drilling hole; the pressure applied in the hydraulic drill pipe 3 is released, at this time, the low-pressure piston 21 and the high-pressure piston 22 are retracted to the initial state under the action of the spring 24. The water in the test drilling hole is communicated with the test section in the drilling hole through the water inlet and outlet hole 13 of the pressure booster device and the push-pull pressure relief conversion device 5;

[0040] Fourth step, to the hydraulic drill pipe 3 inside to apply pressure, low pressure piston 21, force column 23, high pressure piston 22 in the pressure under the action of the low pressure piston 21 and high pressure piston 22 between the air or water is then through the exhaust hole 14 exhaust, high pressure piston 22 moves in the process through the inlet and outlet water hole 14, high pressure piston 22 at this time towards the push and pull pressure relief device 5 side of the second inner cavity 12 is in a sealed state, so as to be able to test section to the specified pressure for pressurization;

[0041] Fifth step, after the ground stress test is finished, unload the pressure in the hydraulic drill pipe 3, low pressure piston 21 and high pressure piston 22 under the action of spring back to the initial state, the hydraulic drill pipe 3 is lifted to drive push and pull pressure relief conversion device 5 to the push and pull pressure relief conversion device 5 and the upper and lower rubber plug 6, 7 communication, so as to unload the pressure in the upper and lower rubber plug 6, 7;

[0042] Sixth step, after the pressure in the upper and lower rubber plug 6, 7 is completely unloaded, the hydraulic drill pipe is lifted or increased to the next selected test position to repeat the above operation.

[0043] The above is only the preferred embodiment of the present application, not therefore limit the embodiments and the scope of protection of the present application, for those skilled in the art, it should be able to realize that the equivalent replacement and obvious changes made by the application of the specification content, the scheme obtained by, should be included in the scope of protection of the present application.

Claims

1. A pressure boosting device for use in in-situ stress testing by hydraulic fracturing, characterized in that, The booster device is sequentially connected with the upper rubber plug and the lower rubber plug of the ground stress testing device through a push-pull pressure relief conversion device, and comprises: A booster cylinder, a first inner cavity and a second inner cavity being in communication with each other are arranged in the booster cylinder, the first inner cavity is connected with the 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 the push-pull pressure relief conversion device, an exhaust hole in communication with the first inner cavity is arranged on the sidewall of the booster cylinder, and an inlet and outlet water hole in communication with the second inner cavity is also arranged on the sidewall of the booster cylinder; A piston device comprising a low-pressure piston movably arranged in the first inner cavity, a high-pressure piston movably arranged in the second inner cavity, and a force transmission column connecting the low-pressure piston and the high-pressure piston; In an initial state, the high-pressure piston is located on one side of the inlet and outlet water hole and is close to the first inner cavity, the low-pressure piston is pressed by the hydraulic device, the low-pressure piston pushes the high-pressure piston to move and the high-pressure piston passes through the inlet and outlet water hole, at this time, the high-pressure piston is in a sealing state towards the second inner cavity on one side of the push-pull pressure relief device, in this state, continue to pressurize, and the passageway of the push-pull pressure relief conversion device is switched to realize pressurization of the upper and lower rubber plugs or pressurization of the test section.

2. The pressurization device for geostress test by hydrofracturing according to claim 1, wherein, The inner diameter of the first inner cavity is greater than the inner diameter of the second inner cavity.

3. The pressurization device for geostress test by hydrofracturing according to claim 2, characterized in that, An elastic reset device is sleeved on the force transmission column, the outer diameter of the elastic reset device is greater than the inner diameter of the second inner cavity and not greater than the inner diameter of the first inner cavity.

4. The pressurization device for geostress test by hydrofracturing according to claim 3, characterized in that, The elastic reset device comprises a spring.

5. The pressurization device for geostress test by hydrofracture method according to claim 1, wherein, The exhaust hole is arranged on the inner wall of the booster cylinder close to the second inner cavity, and the inlet and outlet water hole is arranged on the inner wall of the booster cylinder close to the first inner cavity.

6. The pressurization device for geostress test by hydrofracture method according to claim 1, wherein, The push-pull pressure relief conversion device is connected with the upper rubber plug and the lower rubber plug through a high-pressure oil pipe, in an initial state, the second inner cavity is communicated with 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 downward by a certain distance towards the direction of the upper rubber plug, and the passageway of the push-pull pressure relief conversion device with the upper and lower rubber plugs is disconnected.

Images