Full-bore soluble blanking plug

Abstract

The invention discloses a full-bore soluble blanking plug, which relates to the technical field of under-pressure operation in the petroleum industry, and comprises an upper joint and a lower joint which are in threaded connection, a soluble inner core and a soluble outer sleeve, the soluble inner core is arranged in the soluble outer sleeve, and the outer part of the soluble outer sleeve is tightly connected with the inner side of the upper joint; a step limiting structure used for limiting movement of the soluble inner core is arranged in the soluble outer sleeve, the soluble inner core in the upper connector and the end side, close to the lower connector, of the soluble outer sleeve are wrapped with anti-soluble interlayers, the outer diameter of the soluble outer sleeve is not smaller than the inner diameter of a tubular column, the reverse pressure difference of the soluble blanking plug can reach 70 MPa, the requirement for the pressure of a construction well can be met, and the structure is simple. Meanwhile, after the soluble plug of the soluble blanking plug is dissolved, the full bore of a pipeline can be realized, the later operations of plugging a bridge plug by a steel wire or a cable and the like are not influenced, the soluble blanking plug can be connected to the lowermost part of a pipe column and also can be used for connecting the pipe column, and the problem of poor universality of an existing blanking plug is solved.

Description

Technical Field

[0001] The invention relates to the field of pressure operation technology or other temporary plugging technology in the petroleum industry, and in particular to a full-diameter soluble plugger. Background Art

[0002] Pressure operation refers to the construction work carried out in the wellbore with the help of a pressure operation machine when the wellhead of a gas well or oil-bearing gas well is under pressure. The pressure operation machine mainly includes the operation host and the wellhead blowout preventer group. The host is mainly used to overcome the gravity or uplift of the tubing in the well. The wellhead series blowout preventer combination and the plugging tool in the tubing are used to control the pressure in the well, so as to realize the equipment for lifting and lowering the tubing or rotating operations under pressure at the wellhead. Therefore, during the pressure operation, there is no well suppression, no blowout, and no pressure relief, which can avoid oil and gas layer pollution, maintain formation energy, shorten the operation cycle, zero pollution and other advantages, which is conducive to energy conservation and emission reduction, and stable single well production. It is widely used in the completion, well repair, fracturing and acidizing, hidden danger control, etc. of oil, gas and water wells. It is an important operation technology in the field of international oil and gas field engineering and technical services, and it is also an important technology that the country vigorously develops.

[0003] With the vigorous development of unconventional gas such as shale oil and gas, tight oil and gas, the reservoir is transformed by direct casing sand fracturing and other processes, and then the oil pipe is lowered under pressure to drain water and produce gas. When the well string is completed under pressure, a plug is usually connected to the bottom of the pipe string to seal the inside of the oil pipe hole, and the blowout preventer group of the pressure operation machine is used to seal the oil casing annulus and the lifting and pressing system is used to clamp the pipe string. The oil pipe plug is a key and necessary tool to achieve well completion under pressure.

[0004] At present, the commonly used oil pipe plugs mainly include ceramic plugs and soluble blind plugs. The reverse pressure difference of ceramic plugs can reach 70~105MPa, but ceramic plugs are mostly imported products with high prices and long procurement cycles. Positive pressure holding after well completion will cause ceramic fragments to fall off and cannot reach the full diameter; while the soluble blind plugs in the prior art can generally only withstand a reverse low pressure difference of 35MPa, and can only communicate with the oil casing under positive pressure holding. Moreover, the tubing cannot reach the full diameter after the operation, which limits the later plugging operation, and can only be connected to the lowest part of the tubing and cannot be used to connect the tubing. It has poor versatility and does not meet the pressure level of the construction well.

[0005] For example, the patent document with publication number "CN114320213A" published on April 12, 2022 records a soluble sealing device for pressurized operation, including a working cylinder, a soluble plug, a shear pin, a limit step, an extended protective layer, a first seal, an upper cylinder, a lower cylinder, a second seal, a mounting groove, a blind hole, etc., wherein the soluble plug is subjected to high pressure difference through the limit step, but the soluble plug of the device has a step, and the diameter cannot reach the full diameter after the soluble plug structure is dissolved, which will limit the subsequent plugging operation, etc., and therefore the aforementioned technical problems will also occur; or the diameter at the step is expanded to the full diameter size and can meet the pressure requirements, but the soluble plug will be too large to pass through the lower oil pipe, and a capture basket is required to receive the soluble plug, and it cannot be applied to any position. For another example, the patent document with the publication number "CN215889963U" published on February 22, 2022 records a soluble plug, including a main body and an isolation ring and a soluble plugging body arranged inside the main body, and the isolation ring and the soluble plugging body are arranged parallel to each other, the isolation ring is located at the first end of the soluble plugging body, and an isolation sleeve is arranged at the second end of the soluble plugging body, and a groove is arranged at one end of the isolation sleeve, and the outer periphery of the second end of the soluble plugging body is sleeved into the groove, and O-rings are arranged between the outer periphery of the isolation sleeve and the inner ring of the main body, and between the outer periphery of the isolation ring and the inner ring of the main body, and a first through hole is arranged on the side wall of the main body, and a fixing component is installed in the first through hole, and one end of the fixing component is fixedly connected to the outer periphery of the first end of the soluble plugging body. This design is the same as the above structure. Due to the step of the soluble plugging body, the diameter of the soluble plugging body structure cannot reach the full diameter after dissolution, which will limit the later plugging operations, etc., and can only be connected to the lowest part of the pipe string, and there is also the problem of poor versatility. Summary of the invention

[0006] The purpose of the present invention is to provide a full-diameter soluble plug, the reverse pressure difference of which can reach 70MPa, which can meet the pressure requirements of the construction well. At the same time, after the soluble inner core and the soluble outer shell of the soluble plug are dissolved, the full diameter of the pipeline can be achieved, which can be connected to the lower part of the pipe string and can also be used to connect the middle part of the pipe string. It has good versatility and does not affect the subsequent operations such as wire or cable plugging and bridge plugging.

[0007] The present invention is achieved through the following technical solutions: A full-bore soluble plugger comprises an upper joint and a lower joint connected by threads, a soluble inner core and a soluble outer sleeve, wherein the soluble inner core is placed in the soluble outer sleeve, the outer side of the soluble outer sleeve is tightly connected to the inner side of the upper joint, the interior of the soluble outer sleeve is provided with a step limiting structure for limiting the movement of the soluble inner core, the soluble inner core in the upper joint and the soluble outer sleeve are wrapped with an anti-dissolution barrier layer near the end side of the lower joint, and the outer diameter of the soluble outer sleeve is not less than the inner diameter of the pipe column.

[0008] Furthermore, the soluble inner core and the soluble outer shell have a convex structure near the end of the lower joint.

[0009] Furthermore, the anti-dissolution interlayer is an interlayer made of lead material, and the anti-dissolution interlayer is an arc-shaped structural layer closely attached to the soluble inner core and the soluble outer shell.

[0010] Furthermore, two ends of the anti-dissolution barrier extend into the contact gap between the upper joint and the lower joint.

[0011] Furthermore, the contact surfaces of the soluble inner core, the soluble outer shell and the anti-dissolution barrier are provided with multi-level connection parts.

[0012] Furthermore, the contact surfaces of the soluble inner core, the soluble outer cover and the anti-dissolution barrier are provided with a first horizontal portion, a first inclined portion, a second horizontal portion, a first vertical portion, a third horizontal portion and a second vertical portion in sequence from the inside to the outside.

[0013] Furthermore, a sealing groove I is provided on the outer periphery of the soluble inner core in contact with the soluble outer shell, and a sealing ring is placed in the sealing groove I so that the soluble inner core and the soluble outer shell are tightly sealed.

[0014] Furthermore, a sealing groove II is provided on the outer periphery of the soluble outer sleeve in contact with the upper joint, and a sealing ring is placed in the sealing groove II so that the soluble outer sleeve and the upper joint are tightly sealed.

[0015] Furthermore, the step limiting structure of the soluble outer shell and the soluble inner core can withstand a reverse pressure of at least 70 MPa.

[0016] Furthermore, the soluble inner core and the soluble outer shell are made of magnesium-aluminum alloy.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, without increasing the outer diameter of the entire soluble plug (upper joint and lower joint) (the outer diameter is equivalent to the outer diameter of the coupling), a special design of two components, a soluble inner core and a soluble outer sleeve, is adopted. The soluble outer sleeve is clamped between the upper joint and the lower joint as a soluble support member, and a step limiting structure is designed on the inner side of the soluble outer sleeve to limit the movement of the soluble inner core, which is also equivalent to the "step" part in the prior art. The step limiting structure ensures that the entire plug can withstand sufficient pressure (the expected pressure is above 70MPa) under normal circumstances (undissolved state).

[0018] Second, in the present invention, the soluble plug can be connected to the oil pipe from top to bottom (through the male and female connectors at both ends), and the positive pressure of the oil pipe can knock out the soluble inner core of the soluble plug and can directly pass through the lower oil pipe without being blocked, and does not need to be received by a large inner diameter screen or capture basket; when the soluble outer jacket outside the soluble inner core is also completely dissolved, the soluble plug finally reaches the full diameter, which will not cause the diameter to be limited during the wire plugging operation or the continuous oil pipe operation. In addition, in addition to being suitable for connecting to the lowest part of the pipe string, this soluble plug can also be used to connect to the middle part of the pipe string, and has good versatility.

[0019] 3. Compared with the existing ceramic plug, in addition to being able to be opened by holding pressure through the front eye, the present invention can also use salt water to dissolve soluble materials into powder by pouring salt water into the front eye of the oil pipe to achieve oil-casing communication. This opening method reduces the opening cost of using liquid nitrogen or return fluid to hold pressure.

[0020] Fourth, in the present invention, by adopting a special structure of anti-dissolution barrier, the soluble material is effectively isolated from the complex medium in the well to prevent abnormal dissolution, which is highly safe. In addition, the anti-dissolution barrier is made of soft material and does not affect the later construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the full-bore soluble plugger in the present invention.

[0022] Figure 2 It is a structural schematic diagram of the upper joint.

[0023] Figure 3 It is a partial structural schematic diagram of a full-bore soluble plugger.

[0024] Among them, 1. upper joint; 2. lower joint; 3. soluble inner core; 4. soluble outer shell; 5. step limiting structure; 6. anti-dissolution barrier; 7. raised structure; 8. first horizontal part; 9. first inclined part; 10. second horizontal part; 11. first vertical part; 12. third horizontal part; 13. second vertical part; 14. sealing groove I; 15. sealing groove II; 16. sealing ring; 17. sealing groove III. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0026] Example 1 This embodiment is the most basic implementation method, a full-diameter soluble plug, which relates to the technical field of pressure operation in the oil industry, includes an upper joint 1 and a lower joint 2 connected by thread, a soluble inner core 3 and a soluble outer sleeve 4, and Figure 1The soluble inner core 3 is placed in the soluble outer sleeve 4, the outside of the soluble outer sleeve 4 is tightly connected to the inner side of the upper joint 1, and the inside of the soluble outer sleeve 4 is provided with a step limiting structure 5 for limiting the movement of the soluble inner core 3. The soluble inner core 3 in the upper joint 1 and the soluble outer sleeve 4 are wrapped with an anti-dissolution barrier 6 on the end side close to the lower joint 2, and the outer diameter of the soluble outer sleeve 4 is not less than the inner diameter of the pipe string.

[0027] The soluble plug includes an upper joint 1, a lower joint 2, a soluble inner core 3, a soluble outer shell 4, an anti-dissolution barrier 6 and other structures. The soluble inner core 3 is installed in the soluble outer shell 4, and the anti-dissolution barrier 6 isolates the downhole medium to prevent dissolution and failure during operation. The soluble components (soluble inner core 3, soluble outer shell 4) and the anti-dissolution barrier 6 are installed between the upper joint 1 and the lower joint 2. The upper joint 1 and the lower joint 2 are fixed by threads, and the upper joint 1 withstands the reverse wellbore pressure through the step limit structure 5 in the soluble outer shell 4. After the well completion string is lowered under pressure and the gas tree is installed, the soluble inner core 3 can be knocked out by the positive pressure of the oil pipe, and the soluble components made of soluble materials can be dissolved by injecting salt water into the front eye of the oil pipe to communicate with the oil casing to achieve gas production. As the drainage and gas production process is implemented, the soluble outer shell 4 gradually dissolves, that is, the full-diameter purpose is achieved.

[0028] Example 2 This embodiment is a further optimization of the embodiment 1, and the difference is that the soluble inner core 3 and the soluble outer cover 4 have a convex structure 7 near the end of the lower joint 2. Figure 3 On the one hand, it makes the reverse pressure bearing capacity of the entire soluble plug stronger, and on the other hand, it is beneficial to the sealing between the anti-dissolution barrier 6 of the outer layer of the protruding structure 7 and the upper joint 1 and the lower joint 2, which is beneficial to the effective isolation between the soluble components and the complex media in the well.

[0029] Example 3 Compared with Embodiments 1-2, the present embodiment is different in that the anti-dissolution barrier layer 6 is a barrier layer made of lead material, and the anti-dissolution barrier layer 6 is an arc-shaped structural layer closely attached to the soluble inner core 3 and the soluble outer cover 4.

[0030] Example 4 The difference between this embodiment and embodiments 1-3 is that, Figure 1 The two ends of the anti-dissolution barrier 6 extend into the contact gap between the upper joint 1 and the lower joint 2, so that the isolation effect of the anti-dissolution barrier 6 is better.

[0031] Example 5 The present embodiment is different from the embodiments 1 to 4 in that the contact surfaces of the soluble inner core 3 , the soluble outer cover 4 and the anti-dissolution barrier 6 are provided with multi-level connection parts.

[0032] Preferably, reference Figure 3The contact surfaces of the soluble inner core 3, the soluble outer shell 4 and the anti-dissolution barrier 6 are provided with a first horizontal portion 8, a first inclined portion 9, a second horizontal portion 10, a first vertical portion 11, a third horizontal portion 12 and a second vertical portion 13 from the inside to the outside. The anti-dissolution barrier 6 design of the multi-stage connection portion is more conducive to effectively isolating the soluble components from the complex media in the well, thereby ensuring the safety of the soluble plug.

[0033] Example 6 The difference between this embodiment and embodiments 1-5 is that, Figure 2 A sealing groove Ⅰ14 is provided on the outer periphery of the soluble inner core 3 in contact with the soluble outer cover 4, and a sealing ring 16 is placed in the sealing groove Ⅰ14 to ensure that the soluble inner core 3 and the soluble outer cover 4 are tightly connected.

[0034] Furthermore, a sealing groove II 15 is provided on the outer periphery of the soluble jacket 4 in contact with the upper joint 1 , and a sealing ring 16 is placed in the sealing groove II 15 to ensure that the soluble jacket 4 is tightly connected to the upper joint 1 .

[0035] Example 7 Furthermore, the step limiting structure 5 of the soluble outer cover 4 and the soluble inner core 3 can withstand a reverse pressure of at least 70 MPa. Preferably, the soluble inner core 3 and the soluble outer cover 4 are made of magnesium-aluminum alloy.

[0036] Example 8 In order to facilitate the public to understand the present technical solution, this embodiment takes a certain model of full-bore soluble plugger currently used by our company as an example to further illustrate the present solution.

[0037] In the description of the embodiments of the present invention, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invented product is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0038] refer to Figure 1-3 The full-bore soluble plugger specifically includes an upper joint 1 and a lower joint 2. The upper joint 1 is connected to the upper pipe column through a female buckle, and the lower joint 2 is connected to the lower pipe column through a male buckle. The upper joint 1 and the lower joint 2 are connected by a threaded connection. The advantage of the threaded connection is that the sealing effect is relatively good and it is also convenient for the assembly of structural components. It also includes a soluble inner core 3 and a soluble outer sleeve 4.

[0039] In this embodiment, the soluble inner core 3 is placed in the soluble outer shell 4, the outer surface of the soluble outer shell 4 is tightly connected to the inner side of the upper joint 1, and the soluble outer shell 4 is placed in the groove formed between the upper joint 1 and the lower joint 2. A sealing groove II 15 is provided on the outer periphery of the soluble outer shell 4 in contact with the upper joint 1, and a sealing ring 16 is placed in the sealing groove II 15 to make the soluble outer shell 4 and the upper joint 1 tightly sealed. A sealing groove I 14 is provided on the outer periphery of the soluble inner core 3 in contact with the soluble outer shell 4, and a sealing ring 16 is placed in the sealing groove I 14 to make the soluble inner core 3 and the soluble outer shell 4 tightly sealed.

[0040] In this embodiment, the inside of the soluble outer jacket 4 is provided with a step limit structure 5 for limiting the movement of the soluble inner core 3. To prevent the complex medium in the well from directly contacting the soluble material, the soluble inner core 3 in the upper joint 1 and the soluble outer jacket 4 are wrapped with an anti-dissolution barrier 6 near the end of the lower joint 2, and the outer diameter of the soluble outer jacket 4 is not less than the inner diameter of the pipe string. The soluble inner core 3 and the soluble outer jacket 4 are formed into a convex structure 7 near the end of the lower joint 2, and the anti-dissolution barrier 6 is a barrier made of lead material, and the anti-dissolution barrier 6 is an arc-shaped structural layer close to the soluble inner core 3 and the soluble outer jacket 4.

[0041] In this embodiment, the isolation effect of the anti-dissolution barrier 6 will affect the use effect and safety of the soluble plug. Preferably, both ends of the anti-dissolution barrier 6 extend to the contact gap between the upper joint 1 and the lower joint 2, and the contact surfaces of the soluble inner core 3, the soluble outer cover 4 and the anti-dissolution barrier 6 are provided with multi-level connection parts. Figure 3 The contact surfaces of the soluble inner core 3, the soluble outer cover 4 and the anti-dissolution barrier 6 are provided with a first horizontal portion 8, a first inclined portion 9, a second horizontal portion 10, a first vertical portion 11, a third horizontal portion 12 and a second vertical portion 13 from the inside to the outside. In this way, the contact surfaces of the soluble inner core 3, the soluble outer cover 4 and the anti-dissolution barrier 6 are provided with multi-level connection parts. Through the cooperation of the soluble inner core 3, the soluble outer cover 4, the upper joint 1, the lower joint 2 and the anti-dissolution barrier 6, the anti-dissolution barrier 6 effectively isolates the soluble material from the complex medium in the well, and has high safety.

[0042] In this embodiment, a sealing groove III 17 is provided on the outer periphery of the lower joint 2 , and the upper joint 1 and the lower joint 2 are tightly sealed through the cooperation of the sealing groove III 17 and the sealing ring 16 .

[0043] In this embodiment, the theoretical design value of the reverse pressure bearing capacity of the step limit structure 5 is 140MPa when it is designed. The step limit structure 5 of the soluble outer shell 4 and the soluble inner core 3 can withstand a reverse pressure of at least 70MPa. The design value is twice the safety factor, and the structure is safe and reliable. The soluble inner core 3 and the soluble outer shell 4 are made of magnesium-aluminum alloy, preferably at 93°C, the dissolution rate is less than 40mg / cm 2h. Magnesium-aluminum alloys with yield strength ≥ 350MPa and hardness (HB) ≥ 110.

[0044] The soluble plug in this embodiment was tested under a reverse pressure of 105 MPa and 150°C. After 10 days, the structure was still not damaged and the structural sealing was good. It can be seen that the soluble plug has good reverse pressure bearing capacity and a wide range of applications.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A full-bore soluble plug, characterized in that: The invention comprises an upper joint (1) and a lower joint (2) connected by thread, a soluble inner core (3) and a soluble outer shell (4), wherein the soluble inner core (3) is placed in the soluble outer shell (4), the outer surface of the soluble outer shell (4) is tightly connected to the inner side of the upper joint (1), the inner surface of the soluble outer shell (4) is provided with a step limiting structure (5) for limiting the movement of the soluble inner core (3), the end side of the soluble inner core (3) in the upper joint (1) and the soluble outer shell (4) close to the lower joint (2) is wrapped with an anti-dissolution barrier (6), and the outer diameter of the soluble outer shell (4) is not less than the inner diameter of the pipe string.

2. A full-bore soluble plug according to claim 1, characterized in that: The soluble inner core (3) and the soluble outer shell (4) have a convex structure (7) at the end side close to the lower joint (2).

3. A full-bore soluble plug according to claim 2, characterized in that: The anti-dissolution interlayer (6) is an interlayer made of lead material, and the anti-dissolution interlayer (6) is an arc-shaped structural layer that is closely attached to the soluble inner core (3) and the soluble outer shell (4).

4. A full-bore soluble plug according to claim 1, characterized in that: Both ends of the anti-dissolution barrier (6) extend into the contact gap between the upper joint (1) and the lower joint (2).

5. A full-bore soluble plug according to claim 4, characterized in that: The contact surfaces of the soluble inner core (3), the soluble outer shell (4) and the anti-dissolution barrier (6) are provided with multi-level connection parts.

6. A full-bore soluble plug according to claim 5, characterized in that: The contact surfaces of the soluble inner core (3), the soluble outer shell (4) and the anti-dissolution barrier (6) are provided with a first horizontal portion (8), a first inclined portion (9), a second horizontal portion (10), a first vertical portion (11), a third horizontal portion (12) and a second vertical portion (13) in sequence from the inside to the outside.

7. A full-bore soluble plug according to claim 1, characterized in that: A sealing groove I (14) is provided on the outer periphery of the soluble inner core (3) in contact with the soluble outer shell (4). A sealing ring (16) is placed in the sealing groove I (14) so ​​that the soluble inner core (3) and the soluble outer shell (4) are tightly sealed.

8. A full-bore soluble plug according to claim 1, characterized in that: A sealing groove II (15) is provided on the outer periphery of the soluble outer sleeve (4) in contact with the upper joint (1), and a sealing ring (16) is placed in the sealing groove II (15) so that the soluble outer sleeve (4) and the upper joint (1) are tightly sealed.

9. A full-bore soluble plug according to claim 1, characterized in that: The step-limiting structure (5) of the soluble outer shell (4) cooperates with the soluble inner core (3) to withstand a reverse pressure of at least 70 MPa.

10. A full-bore soluble plug according to claim 1, characterized in that: The soluble inner core (3) and the soluble outer shell (4) are made of magnesium-aluminum alloy.

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