Construction method for enhancing extraction effect of ground coal bed gas

Abstract

The invention relates to a construction method for enhancing the extraction effect of a ground coal bed gas, comprising the following steps of: (1) constructing a vertical cave well, forging caves on coal beds with coal bed gases needed to extract, and placing fiberglass casings into the caves; (2) constructing a vertical well section and a lower branched main horizontal well hole of a horizontal well, respectively forwards constructing the lower branched main horizontal well hole and a horizontal branched well hole positioned in front of a lower branched cave after butting with the vertical cave well, returning to a position nearby the rear end of the vertical cave well and then constructing a horizontal branched well hole positioned at the rear of the lower branched cave; (3) after a lower branched well hole is constructed, carrying out side drilling to construct an upper branched well hole; (4) after an uppermost branched well hole is constructed, plugging inclined well sections of main horizontal well holes inside the horizontal well from a side drilling windowing point to a coal seeing point by using cementing cement; (5) drilling and flushing the vertical cave well, installing discharge and extraction equipment, and extracting the coal bed gas by discharging water and reducing pressure on the ground. The invention can shorten the construction period, reduce the construction and production cost, decrease the lands used for construction and extraction and enhance the extraction effect of the ground coal bed gas.

Description

technical field [0001] The invention belongs to the technical field of coal bed gas exploitation, and in particular relates to a construction method for improving the extraction effect of ground coal bed gas. Background technique [0002] At present, the main ways of producing coalbed methane are: vertical wells on the ground, setting pinnate horizontal wells in the coal seam, starting construction of branch boreholes after the near-end docking horizontal well passes through the cave, and starting construction of branch boreholes after the far-end docking horizontal well passes through the cave. [0003] It has been found through research that, due to the low rate of coal seam drilling, the extraction effect of coalbed methane in vertical wells is not as good as that of horizontal wells to a certain extent. However, horizontal wells have internal flow resistance in the wellbore in the horizontal section. The longer the horizontal section, the greater the internal resistance. ...

AI Technical Summary

Problems solved by technology

If coalbed methane needs to be exploited in multi-layer coal seams, it is necessary to construct multiple groups of horizontal wells to exploit coalbed methane in different coal seams, and more well sites must be built to meet the needs of construction and extraction, which cannot maximize the benefits of input and output change

[0007] To sum up, under the same geological conditions, the existing coalbed methane extraction technology has disadvantages such as small coalbed methane output, high construction and production costs, large land occupation for construction and drainage, and long construction period.

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