IN-SHAFT DRILLING METHOD FOR RECOVERY OF GAS FROM SUBTERRANEAN FORMATIONS

摘要

A method for collecting gas from subterranean formations having a plurality of spaced-apart coal seams containing methane gas includes the steps of drilling a shaft from the earth's surface to a depth sufficient to intersect a plurality of seams containing gas and thereunder to create a sump. A plurality of generally horizontal holes are drilled from the shaft into selected seams and gases collected from the boreholes and conducted through the shafts to the earth's surface. Apparatus, including a movable and rotatable platform, is lowered to a position adjacent the coal seam containing methane gas and an array of generally horizontal holes drilled from the platform into each of the coal seams from which methane gas is to be collected. Liners are inserted in each of the boreholes and interconnected through a riser for conducting the methane gas to the earth's surface. The method and apparatus of the invention enables the collection of methane gas from spaced-apart subterranean seams having narrow thickness.