A shale gas wellhead main control valve replacement device under pressure

Abstract

The invention discloses a pressure-containing replacing device for a main control valve of a shale gas wellhead. The pressure-containing replacing device comprises a blocking mechanism, a feeding-in mechanism, a support mechanism and a lifting mechanism. The blocking mechanism comprises a blocker and a fixing device, both of which are detachably connected. The blocker is used for penetrating through the main control valve to reach at the pre-set position in order to block an oil tube head. The fixing device is used for fixing the blocker to the pre-set position. The feeding-in mechanism comprises a piston-rod type first oil cylinder used for pushing the blocker to the pre-set position. The support mechanism comprises a first flange and a pair of support columns, both of which are detachably connected. The lifting mechanism comprises a pair of second oil cylinders, in shapes of piston rods, located on two sides of the first oil cylinder. Free ends of piston rods of the pair of second oil cylinders are provided with linear members. The linear members are detachably connected with the main control valve and used for lifting the main control valve. The pressure-containing replacing device for the main control valve of the shale gas wellhead has following beneficial effects: characteristics of the shale gas wellhead such as small space and high wellhead pressure are satisfied; pollution of environmental pollution and decrease in output by adoption of a well-killing method are avoided; and the pressure-containing replacing device has low working cost and the blocker has a double-locking function in order to ensure that valve replacing operation is performed safely and reliably.

Description

technical field [0001] The invention relates to the field of pressure operation at the wellhead of shale gas, and more specifically relates to a device for replacing the main control valve of the wellhead of shale gas under pressure. Background technique [0002] my country is rich in shale gas resources, but due to the low permeability of shale formations, shale gas wells need to undergo reservoir reconstruction to obtain ideal production after completion, and hydraulic fracturing is one of the core technologies for shale gas development. During the fracturing construction, since the tubing head and the main control valve are involved in the staged sand injection fracturing construction, the high-pressure working fluid of the wellhead equipment will wash and corrode, which will damage the valve core of the main control valve, resulting in seal failure, and the valve cavity is easy to enter sand, causing the wellhead After fracturing, the pressure test failed and the main cont...

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Problems solved by technology

[0002] my country is rich in shale gas resources, but due to the low permeability of shale formations, shale gas wells need to undergo reservoir reconstruction to obtain ideal production after completion, and hydraulic fracturing is one of the core technologies for shale gas development. During the fracturing construction, since the tubing head and the main control valve are involved in the staged sand injection fracturing construction, the high-pressure working fluid of the wellhead equipment will wash and corrode, which will damage the valve core of the main control valve, resulting in seal failure, and the valve cavity is easy to enter sand, causing the wellhead After fracturing, the pressure test failed and the main control valve was not closed tightly, which led to the following problems: (1) The main control valve located at the outlet of the tubing head is the main switch of the gas production wellhead, and is the most critical cut-off switch. Leakage occurs, and the entire wellhead is in an uncontrolled state, which may cause wellhead accidents, threaten the well site and personal safety, cause waste of underground resources, and pollute the environment; The gas collection (on and off), once installed, is in working condition, so it is extremely difficult to maintain and replace the main control valve

Using this method requires a lot of manpower and material resources, and production must be stopped. After killing the well, the mud impurities in the construction often block the pores of the formation, often reducing gas production, and even causing low-production wells to become dead wells, and it is not suitable for shale. gas; the second is to use slips to locate stuck points for valve replacement or maintenance. This method relies on slips meshing with a fixed point on the inner wall of the pipe head to seal; but because the flow channel of the oil pipe head is corroded by acidic medium due to long-term work, its inner wall is often uneven 1. It is difficult to choose the position of the stuck point, the reliability of the engagement between the chuck and the inner wall is poor, and the safety is not guaranteed, and it is difficult to take it out after changing the valve. Therefore, this method is generally limited to oil and gas wells with well pressure below 20MPa. use

[0004] At present, the technology of replacing wellhead valves under pressure is a very economical technology, but it is also a very risky technology

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