The United States Steel Corp. in cooperation with the U.S. Government is conducting a large-scale methane drainage field demonstration using stimulated vertical boreholes drilled in advance of mining. A grid pattern of 23 boreholes, isolating approximately 1.5 Km2 of coalbed area, was drilled to the lower bench of the Mary Lee coalbed, Jefferson County, Alabama. Upon completion of drilling operations, various hydraulic stimulation treatments utilizing nitrogen-generated foam, water, and gelled fluid were performed to enhance the rate of methane gas removal. Production from the grid pattern began in September 1977 and continued as the last borehole was placed on production during October 1980. To date, in excess of 33,800,000 m3 of methane gas has been drained as a result of this effort. Underground mining operations were approximately 3.2 Km from the grid pattern when production began and have currently progressed to within 1.6 Km. Underground interception of the grid is expected in 1986.
Proc. Australas. Inst. and Metall. Symp., Wollongong, NSW, Australia, May 1982, PP. 81-88