A repeatable coiled tubing bridge plug for multi-stage variable slot fracturing

Abstract

A kind of repeatable coiled tubing bridge plug for multi-section variable card distance fracturing.It mainly solves the problem of poor adaptability caused by card distance fixation when existing coiled tubing carries out multi-layer fracturing.The fishing head (1) is connected to the central tube (10) through the connecting body (3), the connecting body (3) is provided with reset fishing claw (2) outside, the central tube (10) is provided with setting valve (4) inside the upper end, the central tube (10) is provided with secondary unblocking spring claw (13) outside, the secondary unblocking spring claw (13) is connected to the upper connector (6) outside by thread, the upper connector (6) is provided with pressure relief combination valve inside, the upper connector (6) is provided with rubber tube (12) below, the rubber tube (12) is provided with setting piston (14) below, the setting piston (14) is provided with slip assembly below.The coiled tubing bridge plug can realize variable card distance multi-layer fracturing by coiled tubing pressure dragging, and can be smoothly unblocked when accident occurs.

Description

Technical Field

[0001] This invention relates to the field of oilfield production engineering, specifically to a repeatable continuous tubing bridge plug for multi-stage variable clamping distance fracturing. Background Technology

[0002] Currently, the Daqing Oilfield's old areas employ coiled tubing combined with a double-seal single-clamp system for environmentally friendly and precise fracturing. This leverages the pressurized drag capability of coiled tubing to achieve multi-segment, efficient, and environmentally friendly fracturing. However, due to limitations in blowout preventer riser height, the double-seal span is fixed and far less than 10 meters, resulting in poor adaptability for multi-segment fracturing. Many oil layers cannot be modified, hindering precise fracturing. Furthermore, sand accumulation in the middle of the double-seal system can lead to sand jamming in the tubing string. The coiled tubing has a low lifting load and weak unjamming ability, ultimately causing engineering accidents. Summary of the Invention

[0003] To overcome the shortcomings of existing coiled tubing systems with fixed clamping distances during multi-stage fracturing, which result in poor adaptability, this invention provides a repeatable coiled tubing bridge plug for multi-stage variable clamping distance fracturing. This repeatable coiled tubing bridge plug can achieve multi-stage fracturing with variable clamping distance by dragging the coiled tubing under pressure, thereby increasing its adaptability and allowing for easy unclamping in case of accidents.

[0004] The technical solution of the present invention is: a repeatable continuous tubing bridge plug for multi-stage variable clamping distance fracturing, comprising a retrieval head, the lower end of which is connected to a central tube via a connector, a reset retrieval claw on the outside of the connector, a setting valve inside the upper end of the central tube, a secondary release spring claw on the outside of the central tube, an upper connector threadedly connected to the secondary release spring claw, and the upper connector connected to the central tube via a secondary release pin; a pressure relief combination valve inside the upper connector, a rubber sleeve at the lower part of the upper connector, a setting piston at the lower part of the rubber sleeve, and a slip assembly at the lower part of the setting piston.

[0005] The pressure relief combination valve includes a pressure relief valve and a balance valve. The upper connector has a longitudinal through hole, and the lower part of the through hole is equipped with a balance valve. The upper part of the balance valve is equipped with a pressure relief valve. The bottom of the upper connector is threadedly connected to an adjusting ring, and the upper connector has a reset body on the outside.

[0006] The slip assembly includes an upper cone, a piston sleeve, and a lower cone. The piston sleeve is threaded to the outside of the lower end of the setting piston. The upper cone is provided between the piston sleeve and the secondary unsealing spring claw. The outer side of the lower end of the upper cone is engaged with the slip hanger through a step. The slip hanger is provided with slips. The lower end of the slip hanger is connected to the lower cone through a pin. The inner side of the lower cone is provided with a boss, and the boss is located below the step on the outer surface of the central tube.

[0007] The upper outer wall of the connector is provided with several axial grooves. The lower ends of the reset retrieval claws are respectively located in the grooves, and the upper ends of the reset retrieval claws are connected and located outside the retrieval head.

[0008] When pressurizing inside the continuous tubing, the force-bearing area at the lower end of the reset and retrieval claw is greater than that at the lower end of the upper connector, creating a pressure difference that pushes the reset and retrieval claw upward.

[0009] The lower part of the secondary unsealing spring claw body consists of several separate claws. The lower end of each claw has protruding steps on both the inner and outer sides. The outer wall of the lower end of the central tube has a boss. In the initial and fracturing states, the boss is located at the inner step of the claw, supporting the claw. In the unsealing state, the boss is located above the inner step of the claw. The central tube moves upward, and the boss drives the secondary unsealing spring claw upward to achieve unsealing. The central tube has a pressure relief hole and a liquid inlet hole on its side wall. The pressure relief hole is located above the upper end face of the secondary unsealing spring claw, and the liquid inlet hole corresponds to the liquid passage hole in the middle of the secondary unsealing spring claw. The lower end of the outer wall of the setting piston is concave inward. The setting piston, the upper cone, and the secondary unsealing spring claw together form an annular cavity, and the liquid passage hole corresponds to the annular cavity.

[0010] The present invention has the following beneficial effects: By adopting the above-mentioned scheme, the present invention makes full use of the downhole pressure system formed during the fracturing process, takes advantage of the characteristic that the coiled tubing can be dragged under pressure, realizes the anchoring and sealing of the bridge plug by a closed hydraulic system, and realizes the release and reset by the pressure inside the well, thereby realizing multi-stage fracturing with variable clamping distance. Attached Figure Description

[0011] Figure 1 This is a structural schematic diagram of the present invention, where a is the upper half and b is the lower half; Figure 2 This is a schematic diagram of the salvage tube.

[0012] In the diagram: 1-retrieval head, 2-reset retrieval claw, 3-connector, 4-setting valve, 5-secondary unsealing pin, 6-upper connector, 7-pressure relief valve, 8-reset body, 9-balance valve, 10-center tube, 11-adjusting ring, 12-rubber sleeve, 13-secondary unsealing spring claw, 14-setting piston, 15-upper cone, 16-piston sleeve, 17-slip holder, 18-slip, 19-lower cone, 20-plug, 21-pressure relief hole, 22-liquid inlet hole, 31-retrieval cylinder upper connector, 32-reset spring, 33-retrieval body, 34-milling cylinder. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings: Depend on Figure 1As shown, a repeatable continuous tubing bridge plug for multi-stage variable-gap fracturing includes a retrieval head 1. The lower end of the retrieval head 1 is threaded to a connector 3. The bottom of the connector 3 is threaded to a central tube 10, and an anti-rotation pin is provided between the connector 3 and the central tube 10. A reset retrieval claw 2 is provided on the outside of the connector 3. The upper body of the reset retrieval claw 2 is located outside the retrieval head 1, and the lower part consists of several separate retrieval claws. Both the inner and outer ends of the lower ends of the retrieval claws have bosses. The outer wall of the upper end of the connector 3 has several axial grooves, and the bottom of the grooves has recesses that mate with the inner bosses at the lower ends of the retrieval claws. The retrieval claws at the lower ends of the reset retrieval claws 2 correspond one-to-one with the grooves of the connector 3, and are located within the grooves. The inner bosses of the retrieval claws are located within the recesses of the grooves in the connector 3. During pressurization in the continuous tubing, the force-bearing area at the lower end of the reset retrieval claw 2 is greater than the force-bearing area at the lower end of the upper connector 1, creating a pressure difference that pushes the reset retrieval claw 2 upwards.

[0014] The upper end of the central tube 10 is equipped with a setting valve 4, and the lower end is connected to a plug 20. A secondary unsealing spring claw 13 is provided on the outside of the central tube 10. The secondary unsealing spring claw 13 is externally threaded to an upper connector 6, and the upper connector 6 is connected to the central tube 10 via a secondary unsealing pin 5. The lower part of the secondary unsealing spring claw 13 consists of several separate claws. The lower end of each claw has protruding steps both inside and outside. The lower outer wall of the central tube 10 has a boss. In the initial and fracturing states, the boss is located at the inner step of the claw, supporting the claw. In the unsealing state, the boss is located above the inner step of the claw. As the central tube 10 moves upward, the boss can drive the secondary unsealing spring claw 13 upward, which in turn drives the upper connector 6 upward, shearing the secondary unsealing pin 5 and achieving unsealing.

[0015] The upper connector 6 is equipped with a pressure relief combination valve inside. The upper connector 6 has a longitudinal through-hole, and the pressure relief combination valve is located within the through-hole. The pressure relief combination valve includes a pressure relief valve 7 and a balance valve 9. The balance valve 9 is located at the lower part of the through-hole, and the pressure relief valve 7 is located above the balance valve 9. An adjusting ring 11 is threadedly connected to the bottom of the upper connector 6. The adjusting ring 11 can adjust the axial position of the balance valve 9 and the pressure relief valve 7 within the upper connector 6. A reset body 8 is provided on the outside of the upper connector 6. The reset body 8 is a "T-shaped rubber ring" made of HNBR rubber, with its outer surface protruding from the outer wall of the upper connector 6. A rubber sleeve 12 is located below the adjusting ring 11, and a setting piston 14 is located below the rubber sleeve 12. A slip assembly is located below the setting piston 14. The slip assembly includes an upper cone 15, a piston sleeve 16, and a lower cone 19. The piston sleeve 16 is threaded to the outside of the lower end of the setting piston 14. The upper cone 15 is located between the piston sleeve 16 and the secondary release spring claw 13, and a pin is fixed between the piston sleeve 16 and the upper cone 15. The outer side of the lower end of the upper cone 15 engages with the slip holder 17 via a step, and a pin is also provided between the slip holder 17 and the upper cone 15. The slip holder 17 is provided with slips 18, and the lower end of the slip holder 17 is connected to the lower cone 19 via a pin. The lower cone 19 has a boss on its inner side, and the boss is located below the step on the outer surface of the central tube 10. Since the lower part of the claw of the secondary release spring claw 13 is located on the step on the outer surface of the central tube 10, the boss on the inner side of the lower cone 19 is also located below the claw of the secondary release spring claw 13.

[0016] The central tube 10 has a pressure relief hole 21 and a liquid inlet hole 22 on its side wall. The pressure relief hole 21 is located above the upper end face of the secondary unsealing spring claw 13 and corresponds to the pressure relief valve 7. The liquid inlet hole 22 is located in the middle of the central tube 10 and corresponds to the liquid passage hole 23 in the middle of the secondary unsealing spring claw 13. The lower end of the outer wall of the setting piston 14 is concave inward. The lower outer surface of the setting piston 14, the lower end face of the step, the upper end of the upper cone 15, and the outer surface of the secondary unsealing spring claw 13 together form an annular cavity. The liquid passage hole 23 corresponds to the annular cavity. This coiled tubing bridge plug is also used in conjunction with a retrieval cylinder, such as... Figure 2 The system includes a retrieval cylinder upper connector 31, an externally threaded milling sleeve 34 connected to the upper connector 31, a boss on the inner wall of the milling sleeve 34, and an annular cavity formed between the lower part of the upper connector 31 and the milling sleeve 34. A return spring 32 is housed within the annular cavity, and a retrieval body 31 is located below the return spring 32, between the return spring 32 and the boss of the milling sleeve 34. During the retrieval of the coiled tubing bridge plug, the milling sleeve 34 engages with the return body 8.

[0017] During operation, the coiled tubing, carrying a hydraulic anchor, upper packer, retrieval tube, and coiled tubing bridge plug, is lowered into the well. The retrieval body 33 of the retrieval tube suspends the reset retrieval claw 2, and the milling sleeve 34 of the retrieval tube seals with the reset body 8. After the tubing string is in place, hydraulic pressure is applied to the coiled tubing. The hydraulic pressure enters the central tube 10 through the setting valve 4, and then flows through the inlet port 22 and the outlet port 23 into the annular cavity between the setting piston 14, the upper cone 15, and the secondary unsealing spring claw 13. This pushes the upper cone 15, slip hanger 17, and slip 18 downwards, and the slip 18 extends and anchors to the casing. Simultaneously, the hydraulic pressure pushes the setting piston 14 upwards, compressing the rubber sleeve 12 to complete the segmental isolation. Continuing to increase the pressure beyond the wellbore pressure of 15 MPa, the upward force on the reset retrieval claw 2 exceeds the resistance of the retrieval claw, causing the reset retrieval claw 2 to move upwards and retract, disengaging from the retrieval body 33 of the retrieval tube. Stop pressurizing, close the setting valve 4, and seal the high-pressure fluid in the bridge plug, maintaining the bridge plug's anchored seal. Raise the tubing string to release the bridge plug, and raise the upper packer to the upper part of the section to complete section fracturing. After fracturing, lower the tubing string to 2m above the bridge plug, and simultaneously lower the tubing string to retrieve the bridge plug while reverse circulation flushing sand. The end face of the milling sleeve 44 of the retrieval barrel presses down to open the pressure relief valve 7 and the balance valve 9. Simultaneously, the milling sleeve 44 of the retrieval barrel seals with the reset body 8, forming two pressure systems inside and outside the coiled tubing. The balance valve 9 balances the pressure above and below the rubber sleeve 12, releasing pressure at the coiled tubing wellhead. The casing pressure is higher than the coiled tubing internal pressure, and the pressure difference forces the upper cone 15, slip hanger 17, and slip 18 to move upwards, while the setting piston 14 moves downwards. Simultaneously, the fluid inside the bridge plug flows out through the pressure relief hole 21 on the central tube 10 and the pressure relief valve 7, releasing the bridge plug and restoring it to its initial state. Raising the tubing string allows for multi-stage fracturing.

[0018] If an accident occurs during construction and the bridge plug becomes stuck, it cannot be unsealed by forcefully lifting it with a continuous tubing string. Instead, a conventional tubing string can be used. After retrieving the bridge plug, the tubing string is lifted by 12 tons, and the central tube 10 is moved upward. This causes the boss on the bottom outer wall of the central tube 10 to disengage from the lower end of the secondary unsealing spring claw 13. The boss of the central tube 10 then gets stuck on the inner wall step of the secondary unsealing spring claw 13, which in turn moves the secondary unsealing spring claw 13 upward. The secondary unsealing spring claw 13 then moves the upper connector 6 upward, shearing the secondary unsealing pin 5 of the bridge plug, thus unsealing the bridge plug and ensuring construction safety.

Claims

1. A repeatable continuous tubing bridge plug for multi-stage variable clamping fracturing, comprising a retrieval head (1), characterized in that: The lower end of the retrieval head (1) is connected to the central tube (10) through the connector (3). The connector (3) is provided with a reset retrieval claw (2) on the outside. The upper end of the central tube (10) is provided with a setting valve (4). The central tube (10) is provided with a secondary unsealing spring claw (13) on the outside. The secondary unsealing spring claw (13) is threaded to the upper connector (6), and the upper connector (6) is connected to the central tube (10) through a secondary unsealing pin (5). The central tube (10) has a pressure relief hole (21) and a liquid inlet hole (22) on its side wall. The pressure relief hole (21) is located above the upper end face of the secondary unsealing spring claw (13), and the liquid inlet hole (22) corresponds to the liquid passage hole (23) in the middle of the secondary unsealing spring claw (13). The upper connector (6) is equipped with a pressure relief combination valve inside, and a rubber sleeve (12) is provided at the lower part of the upper connector (6). A setting piston (14) is provided at the lower part of the rubber sleeve (12), and a slip assembly is provided at the lower part of the setting piston (14). The pressure relief combination valve includes a pressure relief valve (7) and a balance valve (9). The upper connector (6) has a longitudinal through hole. The lower part of the through hole is equipped with a balance valve (9). The upper part of the balance valve (9) is equipped with a pressure relief valve (7). The bottom of the upper connector (6) is threadedly connected to an adjusting ring (11). The upper connector (6) is equipped with a reset body (8) on the outside. The slip assembly includes an upper cone (15), a piston sleeve (16), and a lower cone (19). The lower end of the outer wall of the setting piston (14) is concave inward. The piston sleeve (16) is threaded to the outside of the lower end of the setting piston (14). The upper cone (15) is provided between the piston sleeve (16) and the secondary unsealing spring claw (13). The setting piston (14), the upper cone (15), and the secondary unsealing spring claw (13) together form an annular cavity. The liquid passage hole (23) corresponds to the annular cavity. The lower cone (19) has a boss on its inner side, and the boss is located below the step on the outer surface of the central tube (10).

2. The repeatable continuous tubing bridge plug for multi-stage variable clamping fracturing according to claim 1, characterized in that: The lower outer side of the upper cone (15) is engaged with the slip hanger (17) by a step. The slip hanger (17) is provided with a slip (18). The lower end of the slip hanger (17) is connected to the lower cone (19) by a pin.

3. The repeatable continuous tubing bridge plug for multi-stage variable clamping fracturing according to claim 2, characterized in that: The upper outer wall of the connector (3) is provided with several axial grooves. The lower ends of the reset retrieval claws (2) are respectively located in the grooves. The upper ends of the reset retrieval claws (2) are connected and located outside the retrieval head (1).

4. The repeatable continuous tubing bridge plug for multi-stage variable clamping fracturing according to claim 3, characterized in that: The lower part of the secondary unsealing spring claw (13) is composed of several separate claws. The lower end of the claws is provided with protruding steps on both the inner and outer sides. The lower outer wall of the central tube (10) is provided with a boss. In the initial state and the fracturing state, the boss is located at the inner step of the claw, supporting the claw. In the unsealing state, the boss is located at the upper part of the inner step of the claw. The central tube (10) moves upward, and the secondary unsealing spring claw (13) moves upward through the boss, thus achieving unsealing.

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