Gas drainage radius of single-seam and cross-seam boreholes

Abstract

In high gas mine, gas needs to be pre-pumped through single-seam boreholes to prevent gas outburst in the working face. The effective drainage radius is an important parameter of borehole drilling and has a direct impact on the borehole design and pumping effect. In accordance with the coal seam gas flow theory, the relationship between the effective drainage radii of the cross- and single-seam boreholes is analyzed. A field test is conducted by using the pressure drop method. Experimental results are in line with the conclusions drawn from the theory. When accurate measurement is not required, the effective drainage radius of the cross-seam borehole is slightly equal to that of the single-seam borehole. Therefore, when the effective drainage radius of the single-seam borehole is difficult to determine, it can be replaced by the effective radius of the cross-seam borehole.