Distribution of methane enrichment zone in abandoned coal mine and methane drainage by surface vertical boreholes: A case study from China

Surface vertical boreholes are directly drilled within the upper part of the methane enrichment zone (MEZ) in the shape of “crab shell”, and a borehole is used to extract multiple gobs around it. For example, the surface borehole 2# is used to extract the methane in the MEZ of gob 1, gob 2 and gob 3.272