Overflow well cementing plug casing pressure stabilizing device

Abstract

The utility model discloses a kind of overflow well cementing plug casing pressure stabilizing devices, comprising: pressurizing pipeline, pressurizing pipeline input end is provided with single-flow valve, pressurizing pipeline output end is provided with adjustable pressure relief valve, pressurizing pipeline middle part is equipped with tee pipe, tee pipe one end outlet is connected with four-way pipe, four-way pipe is communicated with buffer, four-way pipe other end outlet is communicated with casing, tee pipe and the communication pipeline of sleeve are equipped with first gate valve, pressurizing pipeline is equipped with second gate valve and third gate valve respectively set in the two sides of tee pipe. The present application solves the problem that the cost of well killing fluid is high, and well killing fluid has an impact on the performance of cement slurry.

Description

Technical Field

[0001] This utility model relates to the field of wellbore sealing technology, and in particular to a pressure stabilizing device for cement plug casing in overflow wells. Background Technology

[0002] Currently, most oilfields consist of multiple layers, with varying water cut and pressure across different formations. During development, especially in the later stages of water injection development, inter-layer conflicts become increasingly prominent, often necessitating the use of cement plugs to seal lower, temporarily unused or abandoned high-water-cut layers. The general procedure for cement plug injection is as follows: The cement plug injection string (or slurry injection string) is lowered into the casing to a predetermined depth (with the tail end above the formation to be sealed). The wellbore is then cleaned and cooled using a positive water circulation system. Cement slurry is injected into the well through the cement plug injection string and replaced with clean water, allowing the slurry to remain at a predetermined position within the wellbore. The cement plug injection string is then raised approximately 1-2 meters, and reverse circulation is initiated through annular injection to flush out excess cement slurry. During reverse circulation flushing, cement slurry below 2 meters from the tail end of the cement plug injection string cannot be flushed out and solidifies to form a cement plug.

[0003] In actual use, there may be overflow in the lower strata. The injected cement slurry is initially fluid. However, if there is overflow in the lower strata, the overflow will dilute and flush out the cement slurry, and the injected cement slurry cannot be effectively retained in the preset position.

[0004] To address the issues associated with lower-level overflow and upper-level cement plug injection, the current common practice is to kill the well first and then inject the cement plug. This involves first injecting the prepared kill fluid into the wellbore to prevent lower-level overflow. However, this method has several drawbacks: the cost of preparing the kill fluid is high; when injecting the cement plug, the kill fluid must be injected first, followed by cement slurry, and then the kill fluid is used as a displacement fluid, with clean water used to separate the kill fluid and cement slurry. Furthermore, the kill fluid can affect the properties of the cement slurry, leading to significant construction risks. Additionally, when the lower formation pressure is high, there may be no suitable kill fluid well. Currently, another method involves first installing a drillable bridge plug above the overflow layer, and then installing a cement plug on top of the drillable bridge plug. This method involves more steps and is more expensive. Furthermore, after installing a drillable bridge plug or a drillable cement retainer for chemical sealing and plugging, it is impossible to remove the entire bridge plug inside the well using a screw drill during minor repairs. Utility Model Content

[0005] The purpose of this invention is to provide a pressure stabilizing device for cement plug casing in overflow wells. This invention solves the problems of high cost of kill fluid and the impact of kill fluid on the performance of cement slurry.

[0006] To achieve the purpose of this utility model, this utility model provides a pressure stabilizing device for the cement plug casing of an overflow well, comprising: a pressurizing pipeline, a check valve at the input end of the pressurizing pipeline, an adjustable pressure relief valve at the output end of the pressurizing pipeline, a tee pipe installed in the middle of the pressurizing pipeline, a four-way pipe connected to one end of the tee pipe, a buffer connected to the four-way pipe, a casing connected to the other end of the four-way pipe, a first gate valve installed on the connecting pipeline between the four-way pipe and the casing, and a second gate valve and a third gate valve installed on the pressurizing pipeline, the second gate valve and the third gate valve being respectively located on both sides of the tee pipe.

[0007] As a preferred embodiment of this utility model, the buffer includes an upper connector and a cylinder. The cylinder is threaded at both the top and bottom. The upper connector is a through-type structure with threads, and its lower end has an upper connector stop surface. The upper connector is threadedly sealed to the upper end of the cylinder, and a first sealing ring is installed at the connection. The lower connector is a through-type structure with threads, and its upper end has a lower connector stop surface. The lower connector is threadedly sealed to the lower end of the cylinder, and its bottom end is connected to one outlet of the tee pipe. A second sealing ring is installed at the connection. The piston has its outer wall axially sliding in contact with the inner wall of the cylinder, dividing the cylinder interior into an upper chamber and a lower chamber. The piston's upward displacement is limited by the upper connector stop surface, and its downward displacement is limited by the lower connector stop surface. A compression spring is installed inside the upper chamber, with its upper end fixedly connected to the upper connector stop surface. The lower part of the compression spring abuts against the upper surface of the piston to form a metal-to-metal contact.

[0008] As a preferred technical solution of this utility model, the adjustable pressure relief valve is automatically set to release pressure 1-2 MPa higher than the static pressure at the wellhead.

[0009] As a preferred embodiment of this utility model, the input end of the pressurization pipeline is equipped with a pump truck, and the output end of the pressurization pipeline is equipped with a recovery tank.

[0010] As a preferred embodiment of this utility model, the four-way pipe is equipped with a pressure gauge and a shut-off valve. The pressure gauge has an inlet end, and the shut-off valve has an inlet end and an outlet end. The inlet end of the pressure gauge is sealed to the outlet end of the shut-off valve through a flange, and the inlet end of the shut-off valve is connected to the four-way pipe.

[0011] Compared with the prior art, this utility model provides a pressure stabilizing device for cement plug casing in overflow wells, which has the following beneficial effects: it can maintain stable wellbore pressure when the cement plug casing string is stationary, being lifted, or undergoing reverse circulation well washing, suppressing overflow in the lower formation, and allowing cement plug injection into the lower overflow well without well killing, thus solving the problems of high cost, high construction risk, and easy formation pollution caused by existing cement plug injection after well killing.

[0012] When overflow occurs in the lower section of the pre-injected cement plug in an oil-water well, and to prevent overflow from causing cement plug failure, this procedure is used when the wellbore needs to maintain a certain pressure to control the overflow. This procedure is set up at the well site. The outlet end of the first gate valve is connected to the casing, and the pump truck is connected to the inlet end of the check valve. The pressure relief valve is adjusted to the required pressure, the first gate valve is closed, and the second and third gate valves are opened. The pump truck pumps in clean water, which enters the buffer. When the pressure reaches the pressure relief pressure, the adjustable pressure relief valve automatically releases pressure and maintains the preset pressure. The upper part of the buffer cavity is a compression spring, and the lower part is clean water. Opening the first gate valve again can stabilize the pressure in the casing and suppress formation overflow.

[0013] Adjustable pressure relief valve automatically relieves pressure 1-2 MPa above the shut-in static pressure, ensuring no overflow in the well. Raising the cement plug tubing reduces the space occupied by the tubing in the well. Pumped fluid can replenish the annulus of the casing through a check valve, a second gate valve, and a first gate valve. Excess pumped fluid is discharged to the recovery tank through a third gate valve and an adjustable pressure relief valve. The opening and closing of the adjustable pressure relief valve can easily cause instantaneous pressure fluctuations and water hammer. The upper part of the buffer piston is a compression spring, and the lower part is filled with fluid, which can effectively buffer pressure fluctuations. When the pressure is high, fluid enters the buffer, and the piston moves upward to compress the compression spring. When the pressure is low, the reverse action is performed, and the fluid is discharged from the buffer.

[0014] It can maintain stable wellbore pressure and suppress lower formation overflow when the cement plug tubing is stationary, being lifted, or undergoing reverse circulation well washing, and can inject cement plugs into the lower overflow well without controlling the well. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model;

[0016] Figure 2 This is a schematic diagram of the structure of the buffer in this utility model;

[0017] 1 is a pressurization pipeline, 2 is a check valve, 3 is an adjustable pressure relief valve, 4 is a buffer, 5 is a sleeve, 6 is a first gate valve, 7 is a second gate valve, 8 is a third gate valve, 9 is a pump truck, 10 is a recovery tank, 11 is a pressure gauge, 12 is a shut-off valve, 301 is an upper connector, 302 is a cylinder, 303 is an upper connector stop surface, 304 is a first sealing ring, 305 is a lower connector, 306 is a lower connector stop surface, 307 is a second sealing ring, 308 is a piston, 309 is an upper chamber, 310 is a lower chamber, and 311 is a compression spring. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0019] Please see Figure 1 Figure 2 This utility model provides a pressure stabilizing device for the cement plug casing of an overflow well, comprising: a pressurizing pipeline 1, a check valve 2 at the input end of the pressurizing pipeline 1, an adjustable pressure relief valve 3 at the output end of the pressurizing pipeline 1, a tee pipe installed in the middle of the pressurizing pipeline 1, a four-way pipe connected to one end of the tee pipe, a buffer 4 connected to the four-way pipe, a casing 5 connected to the other end of the four-way pipe, a first gate valve 6 installed on the connecting pipeline between the four-way pipe and the casing 5, a second gate valve 7 and a third gate valve 8 installed on the pressurizing pipeline 1, the second gate valve 7 and the third gate valve 8 being respectively located on both sides of the tee pipe.

[0020] In one embodiment of this utility model, the buffer 4 includes an upper connector 301 and a cylindrical body 302. The cylindrical body 302 has threads on both its upper and lower ends. The upper connector 301 is a through-type structure with threads, and its lower end has an upper connector stop surface 303. The upper connector 301 is threadedly sealed to the upper end of the cylindrical body 302, and a first sealing ring 304 is installed at the connection. A lower connector 305 is also included; the lower connector 305 is a through-type structure with threads, and its upper end has a lower connector stop surface 306. The lower connector 305 is threadedly sealed to the lower end of the cylindrical body 302. The bottom end of the lower connector 305 is connected to one end outlet of the tee pipe, and a second sealing ring 307 is installed at the connection; the piston 308 has its outer wall in axial sliding contact with the inner wall of the cylinder 302, dividing the inside of the cylinder into an upper chamber 309 and a lower chamber 310. The upward displacement of the piston 308 is limited by the upper connector stop surface 303, and the downward displacement is limited by the lower connector stop surface 306; the compression spring 311 is installed inside the upper chamber 309, with its upper end fixedly connected to the upper connector stop surface 303, and the lower part of the compression spring 311 abuts against the upper surface of the piston 308 to form a metal contact.

[0021] In one embodiment of this utility model, the adjustable pressure relief valve 3 is automatically set to release pressure 1-2 MPa higher than the static pressure at the wellhead.

[0022] In one embodiment of the present invention, a pump truck 9 is provided at the input end of the pressurization pipeline 1, and a recovery tank 10 is provided at the output end of the pressurization pipeline 1.

[0023] In one embodiment of this utility model, a pressure gauge 11 and a shut-off valve 12 are installed in a four-way pipe. The pressure gauge 11 has an inlet end, and the shut-off valve 12 has an inlet end and an outlet end. The inlet end of the pressure gauge 11 is sealed to the outlet end of the shut-off valve 12 through a flange, and the inlet end of the shut-off valve 12 is connected to the four-way pipe.

[0024] The above are merely preferred embodiments of this utility model, but the scope of protection of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the scope of protection of this utility model.

Claims

1. A pressure stabilizing device for the cement plug casing of an overflow well, characterized in that, include: A pressurized pipeline (1) is provided with a check valve (2) at its input end and an adjustable pressure relief valve (3) at its output end. A tee pipe is installed in the middle of the pressurized pipeline (1). A four-way pipe is connected to one end of the tee pipe, and a buffer (4) is connected to the four-way pipe. A sleeve (5) is connected to the other end of the four-way pipe. A first gate valve (6) is installed on the connecting pipeline between the four-way pipe and the sleeve (5). A second gate valve (6) is installed on the pressurized pipeline (1). 7) and the third gate valve (8), the second gate valve (7) and the third gate valve (8) are respectively set on both sides of the three-way pipe; the buffer (4) includes an upper connector (301), a cylinder (302) and a lower connector (305), the upper and lower ends of the cylinder (302) are provided with threads, the upper connector (301) is a through structure with threads at the lower end, the bottom of the upper connector (301) is provided with an upper connector stop surface (303), and the lower end of the upper connector (301) is connected to the threaded seal. At the upper end of the cylinder (302), a first sealing ring (304) is installed at the connection. The lower connector (305) is a through-hole structure with a threaded upper end. The top of the lower connector (305) is provided with a lower connector stop surface (306). The upper end of the lower connector (305) is connected to the lower end of the cylinder (302) by a threaded seal. The bottom end of the lower connector (305) is connected to one end outlet of the three-way pipe. A second sealing ring (307) is installed at the connection. A piston (308) is connected to the cylinder. The inner wall of the body (302) slides axially, dividing the interior of the cylinder into an upper chamber (309) and a lower chamber (310). The upward displacement of the piston (308) is limited by the upper connector stop surface (303), and the downward displacement is limited by the lower connector stop surface (306). A compression spring (311) is installed inside the upper chamber (309), with its upper end fixedly connected to the upper connector stop surface (303). The lower part of the compression spring (311) abuts against the upper surface of the piston (308) to form a metal contact.

2. The overflow well cement plug casing pressure stabilizing device according to claim 1, characterized in that: The adjustable pressure relief valve (3) is automatically set to release pressure 1-2 MPa higher than the static pressure at the wellhead.

3. The pressure stabilizing device for the cement plug casing of an overflow well according to claim 1, characterized in that: The pressurization pipeline (1) has a pump truck (9) at its input end and a recovery tank (10) at its output end.

4. The overflow well cement plug casing pressure stabilizing device according to claim 1, characterized in that: The four-way pipe is equipped with a pressure gauge (11) and a shut-off valve (12). The pressure gauge (11) has an inlet end, and the shut-off valve (12) has an inlet end and an outlet end. The inlet end of the pressure gauge (11) is sealed to the outlet end of the shut-off valve (12) through a flange, and the inlet end of the shut-off valve (12) is connected to the four-way pipe.

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