A system and method for extracting coalbed methane from an old goaf

Abstract

The invention discloses a system and method for extracting coalbed methane in an old goaf. Draining and drilling is carried out on the coal pillars between the cavities of adjacent goafs, and then sent into the extraction pipe and the grouting pipe in sequence; the valve III is opened , inject cement mortar and coal pillars to form a closed space, open valve I, inject N2 from the ground N2 gas storage tank through the gas booster pump, and inject N2 into the gas injection pipe to fracture the coal pillar; open valve II, through the ground drainage station Drain the coalbed methane with the extraction pipe, and record the initial gas flow rate as A; when the coalbed gas flow rate drops to 30% of the initial gas flow rate A, repeat the N2 displacement of the coalbed methane until the coalbed gas flow rate finally drops to the initial gas flow rate At 16% of A, close valve II to stop coalbed methane extraction. The method improves the coalbed methane extraction rate and prolongs the effective service life of the surface drilling single well.

Description

technical field [0001] The invention relates to a system and method for extracting coalbed methane in an old goaf, and belongs to the technical field of extracting coalbed methane. Background technique [0002] At present, my country mainly adopts surface drilling to extract residual coalbed methane in the old empty area, and the extraction effect is not ideal. When the production of coalbed methane decreases, surface drilling is often abandoned directly. A large amount of underground coalbed methane is fully extracted and utilized, and a large amount of available coalbed methane is still adsorbed in a large amount of unmined coal in the underground. It will take a certain time for this part of coalbed methane to desorb from the adsorption state to the free state. At this time, if the ground drilling is abandoned, a large amount of coalbed methane will be abandoned. The utilization of ground still requires ground purification, which undoubtedly increases the cost. [0003] ...

AI Technical Summary

Problems solved by technology

At present, the gas in the old goaf is mainly drilled from the ground to the upper fissure zone of the goaf to extract the gas in the old goaf. This method is difficult to construct during the drilling construction process, with high accident rates, low porosity, and low output. Small size, high cost, and can only extract gas from a single old empty area

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