A method for surface drilling and extraction of residual coalbed methane in old goaf areas of coal mines

Abstract

The invention discloses a method for surface well drilling extraction of residual coal bed methane in an old mined-out area. The method comprises the following steps: drilled wells with the depths being 3-5 m are constructed downwards along the middle of the old mined-out area from the ground, casing pipes are inserted in the drilled wells, and the drilled wells are continuously constructed downwards from interiors of the casing pipes until the drilled wells enter a curve subsidence zone; the curve subsidence zone is filled with cement mortar along the drilled wells, and a gas seepage preventing layer is formed for preventing CO2 injected into the old mined-out area from leaking to the ground; the drilled wells are constructed again along the interiors of the casing pipes from the ground until the drilled wells reach the junction of a collapsed zone and a fractured zone; extraction pipes are inserted in the drilled wells and used for filling the collapsed zone with CO2, and because the CO2 density is higher than the CH4 density and the adsorbability of broken coal rocks remained in the old mined-out area to CO2 is stronger, CO2 is continuously transported to a lower part of the old mined-out area and original adsorbed CH4 in the old mined-out area is displaced out and transported to the top of the old mined-out area for accumulation and is extracted by the drilled wells. The method can greatly improve the extraction efficiency of gas in the mined-out area and perform seal storage on CO2 to reduce greenhouse gas.

Description

technical field [0001] The invention relates to a method for extracting residual coalbed methane in an old goaf area of ​​a coal mine by ground drilling, and belongs to the technical field of extraction of residual coalbed methane in an old goaf area of ​​a coal mine. Background technique [0002] Carbon dioxide emission reduction and disposal has become a hot research topic in current science. Geological disposal is recognized as one of the effective ways to solve the environmental impact of greenhouse gases. In recent years, with the continuous development of coal seam mining technology, a large number of old empty areas are left after coal mining, and these old empty areas can be used as a good carbon dioxide storage geological body. Due to the low coal recovery rate in our country, there are many coal residues in the old empty area, and the residual coal body has released a considerable amount of coalbed methane resources for a long time and has not been effectively uti...

AI Technical Summary

Problems solved by technology

At present, my country mainly uses ground drilling to extract residual coalbed methane in the old empty area, and the extraction effect is not ideal

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