METHOD FOR EXTRACTING COALBED METHANE IN LOW PERMEABILITY COAL SEAM, AND EXTRACTION WELL PATTERN

摘要

Disclosed are a method for extracting coalbed methane in low permeability coal seam, and an extraction well pattern. The method comprises: determining the direction of maximum principal stress in low permeability coal seam (1); arranging at least two large roadway horizontal wells (3) in the low permeability coal seam (1); arranging multiple production wells at both sides of a horizontal section (31) of each of the at least two large roadway horizontal wells (3), the diameter of each production well (4) being less than the diameter of the horizontal section (31) of the large roadway horizontal well (3); and extracting coalbed methane in the low permeability coal seam (1) by means of the at least two large roadway horizontal wells (3) and the multiple production wells (4). According to the method, by means of the horizontal sections (31) of the large roadway horizontal wells (3) perpendicular to the direction of the maximum principal stress, release of stress in low permeability coal seam is promoted, and more crack passages are formed; then coalbed methane is extracted by means of the at least two large roadway horizontal wells and multiple production wells. The extraction efficiency of coalbed methane in the low permeability coal seam is improved.