A system and method for improving coalbed methane extraction volume in surface drilling and extraction of old gobs

Abstract

The invention discloses a system and a method for improving the coalbed methane extraction volume in the old goaf area of ​​ground drilling and drainage, and belongs to the technical field of coalbed methane extraction. The device drains and drills coal pillars between the cavities of adjacent mined-out areas, sends them into the extraction pipe and injection pipe in turn, and sets the sealing sections I and II; opens valves I and III, and injects 30 min into the injection pipe. ~60 MPa supercritical CO2 until the pressure indication drops sharply; open the valve II to extract the coalbed methane from the surface drainage station, record the initial gas flow, and repeat CO2 flooding when the coalbed gas flow rate drops to 30% of the initial gas flow again Coalbed methane, until the coalbed methane flow finally drops to 16% of the initial gas flow, stop coalbed methane extraction. The invention effectively improves the concentration of the extracted coalbed methane, reduces the cost of separation and purification; adopts the supercritical CO2 jet to crush the coal pillar with low threshold pressure, fast crushing speed, no pollution to the coalbed methane reservoir, and can greatly improve the rock breaking efficiency.

Description

technical field [0001] The invention relates to a system and a method for improving the coalbed methane extraction volume in the old goaf area of ​​ground drilling and drainage, and belongs to the technical field of coalbed methane extraction. 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...

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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