System and method for increasing drainage quantity of coal bed gas of ground well drainage goaf

Abstract

The invention discloses a system and a method for increasing drainage quantity of coal bed gas of a ground well drainage goaf and belongs to the technical field of coal bed gas drainage. The method includes: constructing a drainage well between adjacent goaf holes, sequentially sending a drainage pipe and a flow injection pipe in, and arranging sealing sections I and II; opening a valve I and a valve III, injecting 30-60 MPa of supercritical CO2 into the flow injection pipe until pressure indicating number declines suddenly; opening a valve II to enable a ground drainage station to drain the coal bed gas, recording initial gas flow, repeating replacement of coal bed gas with CO2 when coal bed gas flow declines 30% of the initial gas flow again, and stopping coal bed gas drainage until the coal bed gas flow declines to 16% of the initial gas flow finally. By the system and the method, concentration of drained coal bed gas is increased effectively, and cost for separation and purification is lowered; supercritical CO2 jet flow is adopted to break coal columns, so that threshold pressure is low, breaking speed is high, no pollution is caused to a coal bed gas reservoir, and rock breaking efficiency can be improved substantially.

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

Images