| 摘要 |
A process for underbalanced drilling into multiple formations (12, 14), and dewatering the frilled formations, which includes drilling a first borehole (18) through several coal seams (12, 14) to a certain depth; lowering an upstock (31) on a carrier string to the depth of the upper coal seam; lowering a drill string in the carrier string, and angling off of the upstock (31), to drill a lateral or horizontal borehole within the coal seam; repeating the process for the second coal seam (14); setting a packer (60); retrieving the upstock (31) from the carrier string; lowering an electrical submersible pump(75) to the bottom of the principle borehole (18); collecting methane gas from the two coal seams (12, 14); pumping water from the sump portion to the surface, while gas within the annulus between the carrier string and the outer casing enters the plurality of perforations (65) in the carrier string to be carried up to the surface. |
