Casing drilling technique for over-goaf

Abstract

The invention relates to a coalbed methane mining technology, aims at solving the problem of drilling fluid loss of a goaf in coalbed methane extracting and deep drilling processes, and provides a casing drilling technique for an over-goaf. The casing drilling technique comprises the following steps: driving a first collaring head to drill through a finished drill-hole which is 10m below a weathered bedrock by virtue of a drill stem; arranging a casing on a surface layer of the next open pore to the bottom, and carrying out well cementation with cement; adding cement and returning to the earth surface; driving a second collaring head to drill into a coal seam floor of the goaf by virtue of a casing instead of the drill stem, reserving the casing into a pit shaft as an intermediate casing after second collaring is ended, and carrying out well cementation on the position between the intermediate casing and the borehole wall of the goaf; further driving a third collaring head to drill into a finished drill-hole which is 30m below the next group of coal seam floors by virtue of the drill stem. According to the casing drilling technique, a ground casing drilling technique for preventing leakage loss is adopted, when a drill drills into the coal goaf, heavy leakage loss caused by the goaf is lowered by taking the casing as a liner tube; second casing drilling or multiple casing drilling is carried out; drilling of finishing drilling by taking the next group of coal as a target layer through the goaf is achieved.

Description

technical field [0001] The invention relates to a coalbed gas mining technology, in particular to a casing drilling process method through a goaf. Background technique [0002] Coalbed methane is commonly known as "gas", and its main component is CH4 (methane). It is an unconventional natural gas associated with coal and stored in coal seams in an adsorbed state. The main component is methane. is good fuel. When the air concentration of coalbed methane reaches a certain value, it will explode when it encounters an open flame, which is the root cause of coal mine gas explosion accidents. Therefore, controlling coalbed methane is an important means to reduce accidents. Coalbed methane is directly discharged into the atmosphere, which is very destructive to the atmosphere. Therefore, if coalbed methane is exploited before coal mining, the coal mine gas explosion rate will be reduced by 70% to 85%. Coalbed methane can be used as clean energy for industry and agriculture. ...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the problem of drilling fluid leakage in the goaf during the coalbed methane pumping deep drilling process, the present invention provides a casing drilling process through the goaf

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