Shale gas wellhead device

Abstract

The invention relates to the technical field of shale gas exploitation, and discloses a shale gas wellhead device which is characterized in that an emptying header pipe and a production header pipe are located on the ground outside a square well pool, and emptying end pipelines of an intermediate casing, a surface casing and a production casing are connected to the ground and communicate with the emptying header pipe; emptying end pipelines of the intermediate casing, the surface casing and the production casing are all provided with emptying control valves, and the front ends of the emptying control valves are connected with pressure gauges and matched valves; a wellhead emptying control main valve is arranged on the ground section of the emptying main pipe; blocking the non-emptying end pipeline of the surface casing and the non-emptying end pipeline of the intermediate casing; the oil pipe emptying end pipeline and the oil pipe production end pipeline are connected with oil pipe heads through threaded flanges; a production control main valve is arranged on the ground section at the front end of the anti-freezing agent corrosion inhibitor filling port of the production main pipe; the technical problems that an existing shale gas well head device is complex in pipeline replacement operation, limited in operation space and large in operation risk are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas exploitation, and in particular to a shale gas wellhead device. Background Art

[0002] In shale gas extraction systems, the wellbore, a core component of the wellhead process, plays a crucial role in collecting, regulating, and initially processing shale gas. Specifically, multiple pipelines are meticulously arranged within the wellbore. For example, the production pipeline transports the extracted shale gas to subsequent processing units, while the vent pipeline safely discharges excess or unqualified gas into the atmosphere when necessary, ensuring system pressure balance.

[0003] The wellbore is also equipped with a multi-layer casing structure consisting of production casing, technical casing, and surface casing. The surface casing is used to stabilize the wellbore and prevent stratum collapse; the technical casing is used to isolate different strata and protect the wellbore wall; the production casing is directly connected to the production layer and is responsible for transporting shale gas. A Christmas tree is installed above the wellbore, which is a key device for controlling the shale gas extraction process. The Christmas tree integrates multiple valves and instruments to enable precise control of shale gas flow, pressure, and other parameters, while ensuring the safety and efficiency of the extraction process.

[0004] Although square wells play an important role in shale gas extraction, their existing structures still have defects that cannot be ignored, mainly reflected in the following aspects: Serious corrosion issues: Shale gas contains corrosive media such as carbon dioxide (CO2) and sulfate-reducing bacteria (SRB), posing a serious threat to oil pipes and pipelines. Long-term exposure to these media can lead to electrochemical corrosion of pipes and pipelines, resulting in wall thinning and perforation, seriously impacting the normal extraction and production of shale gas.

[0005] Complex replacement operations: When tubing or pipelines need to be replaced due to corrosion or perforation, the existing process is particularly cumbersome. Since the Christmas tree and tubing or pipelines are often welded together, replacement requires hot work such as cutting and welding, which is not only difficult but also poses a high safety risk. Furthermore, the casing heads and tubing heads of some gas wells are located within the wellbore, creating harsh working conditions in the confined space. The presence of liquid accumulation within the wellbore further exacerbates the operational difficulty and safety risks.

[0006] Long operation cycles impact production: In existing processes, replacing oil pipes or pipelines often requires a series of operations, including shutting in the well, nitrogen replacement, pipeline cutting, welding, and weld flaw detection. This results in a long operation cycle. This not only impacts the normal production of gas wells but also increases production costs and operational risks.

[0007] High safety risks: The combination of hot work and confined space operations creates significant safety risks within existing processes. Improper operation or inadequate safety measures can easily lead to serious accidents such as fires and explosions, causing immeasurable damage to personnel safety and the environment. Summary of the Invention

[0008] The present invention aims to provide a shale gas wellhead device to solve the technical problems of existing shale gas wellhead devices, such as complicated pipeline replacement operation, limited operating space and high operating risks.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solutions: a shale gas wellhead device, comprising a tubing head, a casing head, a square well pool, a vent main pipe, and a production main pipe; the casing head is located in the square well pool and comprises a production casing, a technical casing, and a surface casing; one end of the tubing head is connected to a tubing vent end pipeline, and the other end of the tubing head is connected to a tubing production end pipeline; the two ends of the production casing are respectively connected to a vent end pipeline and a production end pipeline, and the two ends of the technical casing and the surface casing are respectively connected to their own vent end pipelines and non-vent end pipelines; The vent main and production main are located on the ground outside the square well pool; the production casing production end pipeline and the oil pipe production end pipeline are connected to the production main on the ground; the oil pipe vent end pipeline is connected to the surface casing vent end pipeline; the technical casing vent end pipeline, the surface casing vent end pipeline, and the production casing vent end pipeline are connected to the ground; the surface section of the surface casing vent end pipeline is connected to the surface section of the technical casing vent end pipeline, and the surface section of the technical casing vent end pipeline and the surface section of the production casing vent end pipeline are connected to the vent main; A technical casing vent end inner valve is provided between the technical casing and the technical casing vent end pipeline, and a surface casing vent end inner valve is provided between the surface casing and the surface casing vent end pipeline; a technical casing vent control valve is provided on the ground section of the technical casing vent end pipeline, and a pressure gauge and supporting valve are connected to the front end of the technical casing vent control valve; a surface casing vent control valve is provided on the ground section of the surface casing vent end pipeline, and a pressure gauge and supporting valve are connected to the front end of the surface casing vent control valve; a wellhead vent control main valve is provided on the ground section of the vent main pipe; The non-vent end pipeline of the surface casing and the non-vent end pipeline of the technical casing are sealed; the oil pipe head is connected with a threaded flange at the vent end pipeline and the production end pipeline of the oil pipe, and the threaded flange is located above the production casing; a production casing vent control valve is installed on the production casing vent end pipeline, and a pressure gauge is connected to the production casing vent control valve; an antifreeze and corrosion inhibitor filling port is connected to the ground section of the production main pipe, and a production control main valve is provided on the production main pipe in front of the antifreeze and corrosion inhibitor filling port.

[0010] The principle and advantages of this solution are: the casing vent line is connected to the surface and removable, while the valves on the non-vent side of the surface casing and the non-vent side of the technical casing are simultaneously plugged. This allows for later maintenance of the wellhead vent line by simply closing the relevant valves and disassembling the line to isolate the energy, eliminating the need for hot work and improving maintenance efficiency. By placing valves and pressure gauges at key locations, pipeline pressure can be monitored in real time, allowing valves to be quickly closed when necessary to isolate the energy and prevent accidents.

[0011] After the venting end and production end of the tubing are detachable, when the tubing head needs to be replaced due to corrosion or other reasons, it is only necessary to close the relevant valves and disassemble the pipeline to easily complete the disassembly and replacement of the tubing head. There is no need to perform hot work to cut the pipeline, the operation cycle is short, and normal production can be resumed more quickly.

[0012] Preferably, as an improvement, the surface casing non-vented end pipeline and the technical casing non-vented end pipeline are plugged, including: For gas wells with no pressure on the casing head, the ends of the surface casing non-vent end pipeline and the technical casing non-vent end pipeline are sealed by fixing the blind flange with bolts; for gas wells with pressure on the casing head, surface casing non-vent end valves and technical casing non-vent end valves are respectively installed at the ends of the surface casing non-vent end pipeline and the technical casing non-vent end pipeline.

[0013] The beneficial effects of this improvement are: a blind flange is used to seal the non-vent end pipeline of the non-pressurized casing, which is a simple and direct physical isolation to prevent gas leakage; a non-vent end valve is used for the pressurized non-vent end pipeline of the casing, so that the pressure can be isolated by closing the valve when necessary to achieve safe sealing.

[0014] Preferably, as an improvement, sand is used to fill the square well pool so that the technical casing and the surface casing are both located in the sand layer, the production casing is located above the sand layer, and steps are made from the wellhead to the square well pool according to the height of the sand from the wellhead after filling.

[0015] The beneficial effects of this improvement are: due to the sand filling treatment, accumulated water in the square pit will seep into the bottom of the square pit, and technicians can stand above the sand layer, so their operations are not disturbed by the accumulated water. In addition, the operating sections of the technical casing and surface casing are above the ground, which reduces the number of operations in the square pit and allows the technical casing and surface casing to be buried. This leaves space for the production casing that needs to be operated, making it easier for technicians to operate.

[0016] Preferably, as an improvement, the valve connections are all connected by threaded flanges; the technical casing vent control valve and the surface casing vent control valve are both flat gate valves; the production casing vent control valve is a threaded plug valve; the wellhead vent control main valve and the production control main valve are both flat gate valves with figure eight blind plates.

[0017] The beneficial effect of this improvement is that each casing head and valve can be detachably connected, which is convenient for subsequent maintenance and replacement.

[0018] Preferably, as an improvement, the valve handwheel and casing head in the other well pool are subjected to anti-corrosion treatment; the anti-corrosion treatment includes wrapping glass fiber cloth and applying epoxy coal tar at the casing head connection or the valve handwheel installation location, then wrapping a layer of glass fiber cloth, and then applying a layer of epoxy coal tar.

[0019] The beneficial effect of this improvement is that the service life is extended through the two anti-corrosion treatments.

[0020] Preferably, as an improvement, the top of the square well is covered with a grille as a cover plate.

[0021] The beneficial effect of this improvement is that the grille cover acts as a protective barrier, effectively preventing people from accidentally falling into the well, providing additional safety for workers, especially during wellhead operations. The grille structure prevents large debris, tools, or equipment from falling into the well, preventing damage to pipelines and valves within the well, or causing safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a front view of the pipeline connection structure according to an embodiment of the present invention.

[0023] Figure 2 2. It is a top view of the pipeline connection structure according to an embodiment of the present invention.

[0024] The figure marks in the drawings of the specification include: square well pool 1, vent main pipe 2, production main pipe 3, oil pipe vent end pipeline 4, oil pipe production end pipeline 5, production casing vent end pipeline 6, production casing production end pipeline 7, technical casing vent end pipeline 8, surface casing vent end pipeline 9, technical casing vent end inner valve 10, surface casing vent end inner valve 11, blind flange 12, antifreeze and corrosion inhibitor filling port 13, technical casing vent control valve 14, surface casing vent control valve 15, wellhead vent control main valve 16, threaded flange 17, production casing vent control valve 18 and production control main valve 19. DETAILED DESCRIPTION

[0025] The following is further described in detail through specific implementation methods: Example Basically as attached Figure 1 and attached Figure 2 Figure 1 shows a shale gas wellhead assembly, comprising a tubing head, a casing head, a square wellbore 1, a vent header 2, and a production header 3. The square wellbore 1 is concreted and buried below the ground. A grille serves as a cover on the top of the wellbore, and the casing head is located within the wellbore 1. The vent header 2 and production header 3 are connected to the surface. One end of the tubing head is connected to a vent line 4, while the other end is connected to a production line 5.

[0026] The casing head includes production casing, technical casing, and surface casing. The production casing is connected to a vent line and a production line at each end, respectively. The technical casing and surface casing are connected to their respective vent lines and non-vent lines at each end. The production casing production line 7 and the oil tubing production line 5 are connected to the surface production main 3 via a tee. The oil tubing vent line 4 is connected to the surface casing vent line 9 via a tee.

[0027] The technical casing vent end pipeline 8, the surface casing vent end pipeline 9 and the production casing vent end pipeline 6 are connected to the ground; the ground section of the surface casing vent end pipeline 9 is connected to the ground section of the technical casing vent end pipeline 8 through a pipe tee, and the ground section of the technical casing vent end pipeline 8 and the ground section of the production casing vent end pipeline 6 are connected to the vent main pipe 2 through a pipe tee.

[0028] A technical casing vent end inner valve 10 is provided between the technical casing and the technical casing vent end pipeline 8, and a surface casing vent end inner valve 11 is provided between the surface casing and the surface casing vent end pipeline 9. Threaded flanges are installed at the outlets of the technical casing vent end inner valve 10 and the surface casing vent end inner valve 11, so that the technical casing vent end pipeline 8 is connected to the technical casing vent end inner valve 10 via the threaded flange, and the surface casing vent end pipeline 9 is connected to the surface casing vent end inner valve 11 via the threaded flange.

[0029] The surface section of the technical casing vent pipeline is connected via a threaded flange to a 35-65 slab gate valve, serving as the technical casing vent control valve 14. A pressure gauge and a matching plug valve are also connected via a threaded flange to the front of technical casing vent control valve 14. The surface section of the surface casing vent pipeline 9 is connected via a threaded flange to a 35-65 slab gate valve, serving as the surface casing vent control valve 15. A pressure gauge and a matching plug valve are also connected via a threaded flange to the front of surface casing vent control valve 15. A slab gate valve with a splayed blind plate is also connected via a threaded flange to the surface section of the vent main pipe 2, serving as the wellhead vent control valve 16.

[0030] The surface casing non-vented end pipeline and the technical casing non-vented end pipeline are plugged; specifically, for a gas well with no pressure on the casing head, the ends of the surface casing non-vented end pipeline and the technical casing non-vented end pipeline are plugged by fixing the blind flange 12 with bolts.

[0031] For gas wells with casing head pressure, surface casing non-vent end valves and technical casing non-vent end valves are respectively installed at the ends of the surface casing non-vent end pipeline and the technical casing non-vent end pipeline; and the inner valve 10 of the technical casing vent end and the inner valve 11 of the surface casing vent end are kept in the open state, and the technical casing non-vent end valve and the surface casing non-vent end valve are kept in the closed state.

[0032] Both the vent line 4 and the production line 5 are connected to the tubing head using threaded flanges 17, located above the production casing. A threaded plug valve is installed on the production casing vent line 6 as a production casing vent control valve 18, which is threadedly connected to a pressure gauge.

[0033] An antifreeze and corrosion inhibitor filling port 13 is connected to the ground section of the production main pipe 3 through a socket welding pipe platform, and a flat gate valve with an eight-shaped blind plate is connected to the production main pipe 3 at the front end of the antifreeze and corrosion inhibitor filling port 13 through a threaded flange as a production control main valve 19.

[0034] The valve handwheel and casing head in the other well pool 1 are treated with anti-corrosion. At the casing head connection or the valve handwheel installation location, first wrap it with glass fiber cloth, apply epoxy coal tar, then wrap it with another layer of glass fiber cloth, and then apply a layer of epoxy coal tar. Finally, install the valve handwheel according to needs.

[0035] The square well pool 1 is filled with sand so that the technical casing and the surface casing are both located in the sand layer, the production casing is located above the sand layer, and steps are made from the wellhead to the square well pool 1 according to the height of the sand from the wellhead after filling.

[0036] A method for using a shale gas wellhead device is as follows: (1) In the venting state, the shale gas wellhead device needs to safely discharge the fluid in the wellbore into the atmosphere for maintenance, repair or emergency response. At this time, the opening and closing conditions of each valve and pipeline and the flow conditions in the pipeline are as follows: Valve opening and closing conditions: Valve inside the vent end of the technical casing: open to allow the fluid in the technical casing to be discharged through the vent end pipeline of the technical casing.

[0037] Valve inside the surface casing vent end: open to allow the fluid in the surface casing to be discharged through the surface casing vent end pipeline.

[0038] Technical casing non-vent end valve: Close to prevent fluid leakage from the non-vent end.

[0039] Surface casing non-vent end valve: Close to prevent fluid leakage from the non-vent end.

[0040] Technical casing vent control valve: open to control the flow of the technical casing vent end pipeline.

[0041] Surface casing vent control valve: open to control the flow of the surface casing vent end pipeline.

[0042] Wellhead vent control main valve: open to discharge the fluid collected from the vent end pipelines of the technical casing, surface casing and production casing into the vent main pipe.

[0043] Production casing vent control valve: Open or close as needed, usually used to control the discharge of residual fluid in the production casing.

[0044] Production control main valve: Close to prevent fluid leakage through the production main pipe.

[0045] Circulation conditions in the pipeline: The fluids in the technical casing and the surface casing pass through their respective vent end inner valves, vent end pipelines and vent control valves, and are finally collected in the vent main pipe and discharged into the atmosphere.

[0046] The fluid in the production casing (if any) is discharged into the vent main pipe through the production casing vent control valve.

[0047] This solves the problem of long pipeline replacement cycles and the need for hot work and confined space operations in existing shale gas wellhead processes. Furthermore, by connecting the vent and production main pipes to the surface and adding wellhead vent control valves and production control valves, energy isolation is achieved during later maintenance work on the pipelines behind the wellhead vent control valves and production control valves, eliminating the risk of explosions during hot work. Filling the square well with sand eliminates the risk of confined space operations and also eliminates liquid accumulation within the well.

[0048] (2) In the production state, the shale gas wellhead device needs to safely and efficiently transport the fluid (mainly shale gas) in the formation to the production facilities on the ground. At this time, the opening and closing conditions of each valve and pipeline and the flow conditions in the pipeline are as follows: Valve opening and closing conditions: Valve inside the vent end of the technical casing: Close to prevent fluid leakage through the vent end pipeline of the technical casing.

[0049] Valve inside the vent end of the surface casing: Close to prevent fluid leakage through the vent end pipeline of the surface casing.

[0050] Valve at the non-vent end of the technical casing: Close (it may be blocked when there is no pressure) to ensure that the fluid in the technical casing does not leak through the non-vent end.

[0051] Valve at the non-vent end of the surface casing: Close (it may be blocked when there is no pressure) to ensure that the fluid in the surface casing does not leak through the non-vent end.

[0052] Technical casing vent control valve: Close to prevent fluid from being discharged through the technical casing vent end pipeline.

[0053] Surface casing vent control valve: Close to prevent fluid from being discharged through the surface casing vent end pipeline.

[0054] Wellhead vent control main valve: Close to ensure that the vent main pipe is in a closed state.

[0055] Production casing vent control valve: Close to prevent fluid leakage through the production casing vent end pipeline.

[0056] Production control main valve: Opens to allow fluid to be transported through the production main to the production facilities on the surface.

[0057] Circulation conditions in the pipeline: The fluid in the formation (mainly shale gas) enters the wellbore through the production casing, and is then transported to the production facilities on the ground through the production end pipeline of the production casing, the pipe tee and the production main pipe.

[0058] The venting end pipeline and the production end pipeline of the oil pipeline may not participate in fluid transportation under the production state, or perform auxiliary operations (such as pressure monitoring, fluid sampling, etc.) according to specific process requirements.

[0059] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A shale gas wellhead device, comprising a tubing head, a casing head, a square well pool, a venting main pipe and a production main pipe, wherein the casing head is located in the square well pool and comprises a production casing, a technical casing and a surface casing, characterized in that: One end of the tubing head is connected to the tubing vent line, and the other end is connected to the tubing production line. The two ends of the production casing are connected to the vent line and the production line respectively. The two ends of the technical casing and the surface casing are connected to their own vent line and non-vent line respectively. The vent main and production main are located on the ground outside the square well. The production casing production end pipeline and the oil pipe production end pipeline are connected to the production main on the ground, and the oil pipe vent end pipeline is connected to the surface casing vent end pipeline; the technical casing vent end pipeline, the surface casing vent end pipeline, and the production casing vent end pipeline are connected to the ground. The surface section of the surface casing venting end pipeline is connected to the surface section of the technical casing venting end pipeline, and the surface section of the technical casing venting end pipeline and the surface section of the production casing venting end pipeline are connected to the vent main pipe; A technical casing vent end inner valve is provided between the technical casing and the technical casing vent end pipeline, and a surface casing vent end inner valve is provided between the surface casing and the surface casing vent end pipeline; a technical casing vent control valve is provided on the ground section of the technical casing vent end pipeline, and a pressure gauge and supporting valve are connected to the front end of the technical casing vent control valve; a surface casing vent control valve is provided on the ground section of the surface casing vent end pipeline, and a pressure gauge and supporting valve are connected to the front end of the surface casing vent control valve; a wellhead vent control main valve is provided on the ground section of the vent main pipe; The non-vent end pipeline of the surface casing and the non-vent end pipeline of the technical casing are sealed; the oil pipe head is connected with a threaded flange at the vent end pipeline and the production end pipeline of the oil pipe, and the threaded flange is located above the production casing; a production casing vent control valve is installed on the production casing vent end pipeline, and a pressure gauge is connected to the production casing vent control valve; an antifreeze and corrosion inhibitor filling port is connected to the ground section of the production main pipe, and a production control main valve is provided on the production main pipe in front of the antifreeze and corrosion inhibitor filling port.

2. A shale gas wellhead device according to claim 1, characterized in that: Plugging treatment is performed on the non-venting end pipelines of the surface casing and the non-venting end pipelines of the technical casing, including: For gas wells with no pressure on the casing head, the ends of the surface casing non-vent end pipeline and the technical casing non-vent end pipeline are sealed by fixing the blind flange with bolts; for gas wells with pressure on the casing head, surface casing non-vent end valves and technical casing non-vent end valves are respectively installed at the ends of the surface casing non-vent end pipeline and the technical casing non-vent end pipeline.

3. A shale gas wellhead device according to claim 2, characterized in that: Sand is used to fill the square well pool so that the technical casing and surface casing are both located in the sand layer, the production casing is located above the sand layer, and steps are made from the wellhead to the square well pool according to the height of the sand from the wellhead after filling.

4. A shale gas wellhead device according to claim 3, characterized in that: The valve connections are all made of threaded flanges; the technical casing vent control valve and the surface casing vent control valve are both flat gate valves; the production casing vent control valve is a threaded plug valve; the wellhead vent control main valve and the production control main valve are both flat gate valves with splayed blind plates.

5. The shale gas wellhead device according to claim 4, characterized in that: The valve handwheel and casing head in the other well pool are treated with anti-corrosion; the anti-corrosion treatment includes wrapping glass fiber cloth and applying epoxy coal tar at the casing head connection or valve handwheel installation, then wrapping a layer of glass fiber cloth, and then applying a layer of epoxy coal tar.

6. The shale gas wellhead device according to claim 5, characterized in that: The top of the square well is covered with a grille as a cover.

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