Pressure-maintaining and shape-preserving coring tool

Abstract

The invention belongs to the technical field of petroleum and natural gas drilling engineering, and discloses a pressure-maintaining and shape-preserving coring tool. The tool comprises a suspension assembly, an outer cylinder, an inner cylinder, a ball valve and a coring drill bit, the suspension assembly, the outer cylinder and the coring drill bit are sequentially and axially connected, the inner cylinder and the ball valve are both arranged in the outer cylinder, the ball valve is connected to the lower end of the inner cylinder, and an annular space is formed among the inner cylinder, the ball valve and the outer cylinder. A pressure maintaining bushing is inserted into the inner cylinder, the rock core can enter the pressure maintaining bushing through the ball valve, the inner cylinder can be connected with an air source, and the air source is configured to inflate the inner cylinder. The tool further comprises a pressure maintaining assembly, the pressure maintaining assembly comprises a sealing connector, the sealing connector is arranged between the inner barrel and the ball valve and makes sealing contact with the ball valve, and a core catcher is arranged in the sealing connector and used for cutting off the core. The tool is used for coring operation, the integrity rate and the yield rate of a rock core can be effectively guaranteed, and the coring efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas drilling engineering, and particularly relates to a pressure and shape maintaining coring tool. Background Art

[0002] Drilling coring refers to the operation of using a coring tool to take rock samples (cores) from the formation, which is an important means to obtain formation core data. Since the core under the formation has high stability, during the process of pulling out the drill string, as the core is taken out, the temperature of the core in the inner barrel gradually decreases, and the pressure in the inner barrel gradually decreases, resulting in a large loss of oil and gas components of the core, and the physical properties will also change. At the same time, due to the characteristics of the core being hard and fragile, it is easy to break when entering and exiting the barrel, thus seriously affecting the integrity rate and recovery rate of the core. Summary of the Invention

[0003] The purpose of the present invention is to provide a pressure and shape maintaining coring tool for coring operations, which can effectively ensure the integrity rate and recovery rate of the core and improve the coring efficiency.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] There is provided a pressure and shape maintaining coring tool, including a suspension assembly, an outer barrel, an inner barrel, a ball valve, and a coring bit. The suspension assembly, the outer barrel, and the coring bit are axially connected in sequence. The inner barrel and the ball valve are both arranged inside the outer barrel. The ball valve is connected to the lower end of the inner barrel. An annulus is formed between the inner barrel and the ball valve and the outer barrel. A pressure maintaining bushing is inserted into the inner barrel, and the core can enter the pressure maintaining bushing through the ball valve. The inner barrel can be connected to a gas source, and the gas source is configured to inflate the inner barrel. The pressure and shape maintaining coring tool further includes a pressure maintaining assembly arranged inside the outer barrel, including a sealing joint arranged between the inner barrel and the ball valve. The sealing joint is in sealing contact with the ball valve, and a core gripper is arranged inside the sealing joint for cutting the core.

[0006] Preferably, the pressure maintaining assembly further includes a pressurizing joint connected to one end of the inner barrel away from the sealing joint, and the gas generated by the gas source can flow to the inner barrel through the pressurizing joint.

[0007] Preferably, an injection valve is arranged on the pressurizing joint, and a first flow channel is arranged axially on the pressurizing joint, and the first flow channel can communicate with the inner cavity of the inner barrel.

[0008] Preferably, the pressure maintaining assembly further includes an inner cylinder joint disposed between the pressurizing joint and the inner cylinder. A pressure compensating valve is provided on the inner cylinder joint, and a second flow channel is provided on the pressurizing joint. One end of the second flow channel communicates with the first flow channel, and the other end communicates with the inner cavity of the inner cylinder. The pressure compensating valve is used to control the on-off of the first flow channel and the inner cavity of the inner cylinder.

[0009] Preferably, a first seal is provided on the surface of the sealing joint facing the ball valve, and the sealing joint is in sealing contact with the ball valve through the first seal.

[0010] Preferably, first inclined surfaces and second inclined surfaces are respectively provided on the surfaces of the sealing joint and the ball valve facing each other, and the first seal is disposed between the first inclined surface and the second inclined surface.

[0011] Preferably, the first seal is a vulcanized rubber pad.

[0012] Preferably, the inner diameter of the sealing joint gradually decreases from the end connected to the inner cylinder to the other end.

[0013] Preferably, the pressure maintaining bushing is made of PVC material.

[0014] Preferably, it further includes a ball valve chamber connected to the lower end of the inner cylinder. The sealing joint and the ball valve are both disposed in the ball valve chamber. A second seal is provided between the inner cylinder and the ball valve chamber, and the second seal is used to seal and fill the gap between the ball valve chamber and the inner cylinder.

[0015] Advantages of the present invention: The pressure maintaining and shape maintaining coring tool provided by the present invention uses the cooperation of the inner cylinder and the pressure maintaining bushing to provide double protection for the core, making the core not easily broken; since the pressure maintaining bushing is inserted into the inner cylinder, when taking out the core, the pressure maintaining bushing is pulled out from the inner cylinder, and the core can be taken out, thus ensuring the integrity of the core structure during the core taking process. The inner cylinder can be connected to a gas source, and the inner cylinder can be inflated through the gas source to compensate the pressure of the inner cylinder, avoiding the reduction of the inner cylinder pressure caused by the temperature drop during the drilling lifting process; after the ball valve is closed, due to the sealing contact between the sealing joint and the ball valve, the sealing performance of the inner cylinder is ensured, further ensuring the pressure inside the inner cylinder; to reduce the change of the physical properties of the core during the drilling lifting and core ground treatment processes, and improve the core recovery rate and core integrity. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the pressure maintaining and shape maintaining coring tool provided by the present invention before differential movement;

[0017] Figure 2 is Figure 1 a partial view of

[0018] Figure 3 Yes Figure 1 Enlarged view of point A in the middle;

[0019] Figure 4 This is a schematic diagram of the structure of the pressure-maintaining and shape-maintaining coring tool provided by the present invention after differential operation.

[0020] In the picture:

[0021] 1. Suspension assembly; 11. Positioning joint; 12. Suspension joint; 13. Release joint; 131. Second limit groove; 14. Socket joint; 15. Pin; 16. Limit block; 17. Pressure relief hole; 2. Outer tube; 3. Inner tube; 31. Pressure-maintaining bushing; 4. Ball valve; 5. Coring drill bit; 6. Sealing joint; 61. Core claw; 62. First sealing element; 7. Pressurization joint; 71. Gas injection valve; 8. Inner tube joint; 81. Supplementary pressure valve; 9. Ball valve compartment; 10. Diverter joint; 100. Pressurization steel ball. Specific implementation method

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only show parts related to the present invention, rather than all structures.

[0023] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0025] In the description of this embodiment, the orientation or positional relationships such as "upper", "lower", "right", etc. are based on the orientation or positional relationships shown in the drawings. It is only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0026] Referring to Figures 1 to 4 , this embodiment provides a pressure-holding and shape-preserving coring tool for coring operations, which can effectively ensure the integrity rate and recovery rate of the core and improve the coring efficiency. The tool includes a suspension assembly 1, an outer barrel 2, an inner barrel 3, a ball valve 4, and a coring bit 5. The suspension assembly 1, the outer barrel 2, and the coring bit 5 are axially connected in sequence. The inner barrel 3 and the ball valve 4 are both arranged inside the outer barrel 2. The ball valve 4 is connected to the lower end of the inner barrel 3. An annulus is formed between the inner barrel 3 and the ball valve 4 and the outer barrel 2. A pressure-holding bushing 31 is inserted into the inner barrel 3. The core can enter the pressure-holding bushing 31 through the ball valve 4. The inner barrel 3 can be connected to a gas source, and the gas source is configured to inflate the inner barrel 3. The tool further includes a pressure-holding assembly, which is arranged inside the outer barrel 2 and includes a sealing joint 6. The sealing joint 6 is arranged between the inner barrel 3 and the ball valve 4. The sealing joint 6 is in sealed contact with the ball valve 4. A core catcher 61 is arranged inside the sealing joint 6, and the core catcher 61 is used to cut the core.

[0027] For the pressure-holding and shape-preserving coring tool provided in this embodiment, the inner barrel 3 and the pressure-holding bushing 31 cooperate to provide double protection for the core, making the core not easily broken; since the pressure-holding bushing 31 is inserted into the inner barrel 3, when taking out the core, the pressure-holding bushing 31 is pulled out of the inner barrel 3, and the core can be taken out, thus ensuring the integrity of the core structure during the core-taking process. The inner barrel 3 can be connected to a gas source, and the gas source can inflate the inner barrel 3 to replenish the pressure of the inner barrel 3, avoiding the reduction of the pressure of the inner barrel 3 caused by the temperature drop during the drill-pulling process; after the ball valve 4 is closed, due to the sealed contact between the sealing joint 6 and the ball valve 4, the sealing performance of the inner barrel 3 is ensured, and further the pressure inside the inner barrel 3 is ensured; to reduce the change of the physical properties of the core during the drill-pulling and core ground treatment processes, and improve the coring recovery rate and core integrity.

[0028] Optionally, referring to Figure 1 and Figure 2, on one side of the sealing joint 6 facing the ball valve 4, a first seal 62 is provided. The sealing joint 6 is in sealing contact with the ball valve 4 through the first seal 62. The first seal 62 can seal and fill the gap between the sealing joint 6 and the ball valve 4, thus ensuring the sealing performance of the inner cylinder 3. Further, on the sides of the sealing joint 6 and the ball valve 4 facing each other, a first inclined surface and a second inclined surface are respectively provided, and the first seal 62 is arranged between the first inclined surface and the second inclined surface. The first inclined surface and the second inclined surface can increase the contact area between the sealing joint 6 and the ball valve 4. By arranging the first seal 62 between the first inclined surface and the second inclined surface, the sealing performance between the sealing joint 6 and the ball valve 4 is further improved, and thus the pressure of the inner cylinder 3 is ensured.

[0029] Preferably, the first seal 62 is a vulcanized rubber pad. In this embodiment, the vulcanized rubber pad is arranged on the first inclined surface of the sealing joint 6. Such an arrangement can improve the stability of the limit between the first seal 62 and the sealing joint 6 and the ball valve 4, and prevent the first seal 62 from falling off. The vulcanized rubber pad has a high hardness and can resist high temperature, and can be applied to high-temperature and high-pressure wells, with remarkable oil and pressure preservation effects.

[0030] Preferably, the inner diameter of the sealing joint 6 gradually decreases from the end connected to the inner cylinder 3 to the other end, so as to be adapted to the core catcher 61.

[0031] Optionally, it further includes a ball valve chamber 9. The ball valve chamber 9 is connected to the lower end of the inner cylinder 3. The sealing joint 6 and the ball valve 4 are both arranged in the ball valve chamber 9. A second seal is arranged between the inner cylinder 3 and the ball valve chamber 9, and the second seal is used to seal and fill the gap between the ball valve chamber 9 and the inner cylinder 3. The arrangement of the second seal ensures the sealing performance between the ball valve chamber 9 and the inner cylinder 3. Preferably, the second seal is a vulcanized sealing pad. Optionally, the inner cylinder 3 is threadedly connected to the ball valve chamber 9.

[0032] Optionally, the pressure-holding bushing 31 is made of PVC material. The PVC material is inexpensive and easy to obtain. At the same time, the surface is smooth, which can reduce the friction between the pressure-holding bushing 31 and the core, enabling the core to smoothly enter the inner cylinder 3 and effectively protecting the core. In addition, the pressure-holding bushing 31 made of PVC material is also convenient for operations such as cutting, encapsulating, and sampling the core after the core is taken out.

[0033] Optionally, the pressure-holding assembly further includes a pressure-adding joint 7. The pressure-adding joint 7 is connected to the end of the inner cylinder 3 away from the sealing joint 6, and the gas generated by the gas source can flow to the inner cylinder 3 through the pressure-adding joint 7. The gas source can inflate the inner cavity of the inner cylinder 3 through the pressure-adding joint 7 to replenish the pressure in the inner cylinder 3, so as to avoid the reduction of the pressure in the inner cylinder 3 due to the decrease in temperature during the process of pulling out the drill string. Exemplarily, the gas source is an air pump, and the gas filled is nitrogen.

[0034] Further, an air injection valve 71 is provided on the pressure connection joint 7. The pressure connection joint 7 is axially provided with a first flow channel, and the first flow channel can communicate with the inner cavity of the inner cylinder 3. Gas can be filled into the pressure connection joint 7 through the air injection valve 71. When the first flow channel communicates with the inner cavity of the inner cylinder 3, the gas in the pressure connection joint 7 can rush into the inner cylinder 3, thereby filling gas into the inner cylinder 3.

[0035] Optionally, the pressure maintaining assembly further includes an inner cylinder joint 8. The inner cylinder joint 8 is arranged between the pressure connection joint 7 and the inner cylinder 3. A pressure replenishing valve 81 is provided on the inner cylinder joint 8. The pressure connection joint 7 is provided with a second flow channel. One end of the second flow channel communicates with the first flow channel, and the other end communicates with the inner cavity of the inner cylinder 3. The pressure replenishing valve 81 is used to control the on-off of the first flow channel and the inner cavity of the inner cylinder 3. Specifically, before the coring tool is lowered into the well, first, gas is injected into the pressure connection joint 7 through the air injection valve 71. At this time, the pressure replenishing valve 81 is closed, and the first flow channel and the second flow channel are not connected. When tripping out, the ball valve 4 is closed, so that the inner cylinder 3 can be closed. At this time, the pressure replenishing valve 81 is opened to connect the first flow channel and the second flow channel. The gas in the pressure connection joint 7 can then enter the inner cylinder 3, thereby replenishing the air in the inner cylinder 3 and preventing the pressure in the inner cylinder 3 from decreasing due to temperature drop during tripping out.

[0036] Optionally, referring to Figure 1 and Figure 3 , the suspension assembly 1 includes a positioning joint 11, a suspension joint 12, a release joint 13 and a receiving joint 14. One end of the suspension joint 12 is threadedly connected to the positioning joint 11, and the other end is connected to the outer cylinder 2. The release joint 13 is inserted into the positioning joint 11 with a clearance. A pin 15 is radially inserted through the release joint 13 and the positioning joint 11 to limit the release joint 13 on the positioning joint 11. A limiting hole is radially provided on the positioning joint 11, and a limiting block 16 is arranged in the limiting hole. A first limiting groove opposite to the limiting block 16 is provided on the suspension joint 12, and the limiting block 16 is snapped into the first limiting groove to prevent axial movement between the release joint 13 and the suspension joint 12. A second limiting groove 131 is provided on the side wall of the release joint 13, and the release joint 13 can axially move to make the limiting block 16 snap into the second limiting groove 131. The receiving joint 14 is arranged in the suspension joint 12 and is threadedly connected to the lower end of the positioning joint 11. Pressure relief holes 17 are provided on the suspension joint 12, the release joint 13 and the receiving joint 14. The inner cavities of the positioning joint 11, the release joint 13 and the receiving joint 14 communicate to form a drilling fluid channel, and the drilling fluid channel communicates with the annulus between the inner cylinder 3 and the outer cylinder 2. When the limiting block 16 is snapped into the second limiting groove 131, the pressure relief hole 17 of the release joint 13 communicates with the pressure relief hole 17 of the receiving joint 14. It should be noted that the structure and principle of the suspension assembly 1 are both prior arts, and will not be described in detail in this embodiment.

[0037] Furthermore, the pressure-maintaining and conformal coring tool further comprises a diverter joint 10, which is arranged between the receiving joint 14 and the pressurizing joint 7, and two third flow channels are arranged on the diverter joint 10, through which the drilling fluid can flow into the annulus.

[0038] Using the pressure-maintaining and shape-maintaining coring tool provided in this embodiment includes the following steps:

[0039] S1. Before drilling, first fill the pressure joint 7 with nitrogen through the gas injection valve 71. The pressure of the nitrogen is 1.5 times the pressure of the bottom hole liquid column (for example, when the bottom hole pressure is 20MPa, 30MPa nitrogen pressure is injected into the pressure joint 7). After the pressure joint 7 is fully pressurized, assemble the coring tool and put it into the well.

[0040] S2, ball valve 4 is in open state, core drill 5 drills into the core, and the drilled core enters inner tube 3 through ball valve 4; after the core is drilled, pressurized steel ball 100 is dropped from the wellhead to make the inner tube 3 and outer tube 2 differential, and ball valve 4 rotates 90 degrees during the differential process to close the inner tube 3, and differential process pressure relief valve 81 is opened at the same time to make the nitrogen in the pressure relief joint 7 enter the inner tube 3 to continuously supplement the pressure of the inner tube 3 to prevent the pressure of the inner tube 3 from decreasing due to temperature drop during the drilling process.

[0041] Specifically, see Figure 1 and Figure 4 , after adding the pressurized steel ball 100, the pressurized steel ball 100 falls on the limiting structure at the bottom of the release joint 13, thereby blocking the drilling fluid channel. When the pump pressure rises by 5MPa-10MPa, the pin 15 between the positioning joint 11 and the release joint 13 is cut off. At this time, the release joint 13 loses its limit and moves downward under the push of the hydraulic force until it abuts against the end limit at the top of the receiving joint 14. In this process, the outer cylinder 2 squeezes the limit block 16 inward under the action of its own gravity, so that the limit block 16 is stuck in the second limit groove 131 on the side wall of the release joint 13. Optionally, the limiting structure is a step structure arranged on the inner wall of the release joint 13. Furthermore, a groove is arranged circumferentially on the release joint 13. During the downward movement of the release joint 13, the end of the receiving joint 14 slides and cooperates with the groove until the end of the receiving joint 14 abuts against the side wall of the groove.

[0042] S3. After the differential operation is completed, the pressure relief holes 17 on the release joint and the receiving joint 14 are connected, the drilling fluid establishes normal circulation, and the pump pressure drops back to normal.

[0043] S4. After the coring tool reaches the ground, it is tested, depressurized and cored out. When cored out, the inner tube joint 8 is removed, the ball valve 4 is opened, and the pressure-maintaining bushing 31 is pulled out from the upper part of the inner tube 3 to take out the core together, ensuring that the core is structurally intact during the cored out process.

[0044] S5. Cut, encapsulate, and sample the pressure-holding bushing 31 and the core to complete the coring operation.

[0045] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments, and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A pressure-maintaining and conformal coring tool, comprising a suspension assembly (1), an outer cylinder (2), an inner cylinder (3), a ball valve (4) and a coring drill bit (5), wherein the suspension assembly (1), the outer cylinder (2) and the coring drill bit (5) are axially connected in sequence, the inner cylinder (3) and the ball valve (4) are both arranged in the outer cylinder (2), the ball valve (4) is connected to the lower end of the inner cylinder (3), and an annulus is formed between the inner cylinder (3) and the ball valve (4) and the outer cylinder (2), characterized in that: A pressure-maintaining bushing (31) is inserted into the inner cylinder (3), and the core can enter the pressure-maintaining bushing (31) through the ball valve (4). The inner cylinder (3) can be connected to a gas source, and the gas source is configured to inflate the inner cylinder (3); The pressure-maintaining conformal coring tool also includes a pressure-maintaining component, which is arranged in the outer tube (2) and includes a sealing joint (6). The sealing joint (6) is arranged between the inner tube (3) and the ball valve (4). The sealing joint (6) is in sealing contact with the ball valve (4). A core claw (61) is arranged in the sealing joint (6), and the core claw (61) is used to cut the core.

2. The pressure-maintaining and shape-maintaining coring tool according to claim 1, characterized in that: The pressure-maintaining assembly further comprises a pressure-increasing joint (7), wherein the pressure-increasing joint (7) is connected to an end of the inner tube (3) away from the sealing joint (6), and the gas generated by the gas source can flow to the inner tube (3) via the pressure-increasing joint (7).

3. The pressure-maintaining and conformal coring tool according to claim 2, characterized in that: The pressurizing joint (7) is provided with an injection valve (71), and the pressurizing joint (7) is provided with a first flow channel along the axial direction, and the first flow channel can be communicated with the inner cavity of the inner tube (3).

4. The pressure-maintaining and shape-maintaining coring tool according to claim 3, characterized in that: The pressure-maintaining assembly further comprises an inner tube joint (8), wherein the inner tube joint (8) is arranged between the pressurizing joint (7) and the inner tube (3), and a pressure-compensating valve (81) is arranged on the inner tube joint (8). The pressurizing joint (7) is provided with a second flow channel, wherein one end of the second flow channel is connected to the first flow channel, and the other end is connected to the inner cavity of the inner tube (3), and the pressure-compensating valve (81) is used to control the connection and disconnection between the first flow channel and the inner cavity of the inner tube (3).

5. The pressure-maintaining and conformal coring tool according to claim 1, characterized in that: A first sealing member (62) is provided on a side of the sealing joint (6) facing the ball valve (4), and the sealing joint (6) is in sealing contact with the ball valve (4) via the first sealing member (62).

6. The pressure-maintaining and shape-maintaining coring tool according to claim 5, characterized in that: The sealing joint (6) and the ball valve (4) are respectively provided with a first inclined surface and a second inclined surface on one side facing each other, and the first sealing member (62) is arranged between the first inclined surface and the second inclined surface.

7. The pressure-maintaining and shape-maintaining coring tool according to claim 5, characterized in that: The first sealing member (62) is a vulcanized rubber pad.

8. The pressure-maintaining and shape-maintaining coring tool according to any one of claims 1 to 7, characterized in that: The inner diameter of the sealing joint (6) gradually decreases from one end connected to the inner tube (3) to the other end.

9. The pressure-maintaining and shape-maintaining coring tool according to any one of claims 1 to 7, characterized in that: The pressure-maintaining bushing (31) is made of PVC material.

10. The pressure-maintaining and shape-maintaining coring tool according to any one of claims 1 to 7, characterized in that: It also includes a ball valve bin (9), which is connected to the lower end of the inner tube (3), the sealing joint (6) and the ball valve (4) are both arranged in the ball valve bin (9), and a second sealing member is arranged between the inner tube (3) and the ball valve bin (9), and the second sealing member is used to seal and fill the gap between the ball valve bin (9) and the inner tube (3).

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