Gas drilling wellhead device without borehole and method for drilling stratum surface layer

Abstract

The invention discloses a gas drilling wellhead device without a borehole and a method for drilling a stratum surface layer. The device comprises a supporting sealing cylinder, a sealed outer housing,and a rotating sealing device. An upper part of the supporting sealing cylinder is provided with a raised edge. External threads are arranged below the raised edge. The supporting sealing cylinder isconnected with the sealed outer housing through a flange in a sealed manner. The side wall of the sealed outer housing is provided with a bypass, an inner wall is provided with steps, and a top is screwed with an upper cover. An upper sealing body and a lower sealing body of the rotating sealing device are connected in a sealed manner, a holding cavity is formed in the rotating sealing device, aninner rotating cylinder is mounted in the holding cavity, the bottom of the inner rotating cylinder is fixedly provided with a rubber core, and an outer side is provided with a thrust bearing. The rotating sealing device is arranged in the sealed outer housing in a sealed manner. When an upper cover of the sealed outer housing is screwed with the sealed outer housing, positions of the upper sealing body and the lower sealing body of the rotating sealing device are fixed. The supporting sealing cylinder is used to embed the gas drilling wellhead device into a stratum and isolate a near-surfacestratum. Under a condition without a borehole, a wellhead sealing device is established. The device is suitable for shallow stratum low-pressure gas to drill a stratum surface layer and establish a borehole.

Description

technical field [0001] The invention relates to gas drilling in the technical field of petroleum drilling, in particular to a wellhead device for gas drilling without a borehole and a method for drilling the surface layer of a stratum. Background technique [0002] Gas drilling technology uses gas as the circulating medium in the wellbore, and a special wellhead device seals the wellhead to prevent uncontrolled discharge of cuttings entrained by the high-speed return gas at the well site. The pressure is far less than the hydrostatic column pressure of conventional liquid drilling fluid. Gas drilling technology can not only save the cost of drilling fluid, but also completely solve the problem of drilling formation loss and increase the mechanical speed of penetration. [0003] At present, gas drilling technology can only be used in subsequent well sections with special wellhead devices installed after casing cementing. However, when some formations are drilled into the fo...

AI Technical Summary

Problems solved by technology

However, when some formations are drilled into the formation surface, serious leakage problems will be encountered. Drilling fluid leaks into the formation, which not only affects normal drilling, but also pollutes the soil because of the shallow depth of the formation surface. and formation water

If the gas drilling technology is adopted, the leakage problem of formation surface drilling can be solved, but because the formation has not been drilled, there is no wellbore, let alone casing cementing, and the wellhead cannot be installed, so gas drilling cannot be carried out

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