Mining Publication: Directional Drilling For Coalbed Degasification: Program Goals and Progress in 1978

The Bureau of Mines is cooperating with the U.S. Department of Energy in a directional degasification project at the Emerald Mine near Waynesburg, Pennsylvania. This project is designed to combine the highly successful underground horizontal degasification technology with surface drilling methods. The objective of this program is to demonstrate that directional drilling can be used as a technique for degasifying coalbeds ahead of mining to reduce the hazards of methane-air explosions in coal mines. The directional hole at the Emerald Mine is designed to start vertically and enter the Pittsburgh coalbed horizontally. A 3-inch pilot hole entered the Pittsburgh coalbed at a vertical depth of 999 feet. The hole will be reamed to 8 3/4 inches in diameter, and 5 1/2-inch casing will be cemented in place. Three individual 3-inch-diameter, 3,000-foot horizontal gas collection holes will be drilled into the coalbed in a "bird foot" pattern. A corehole and vertical dewatering hole have been completed at the anticipated coalbed intercept. The dewatering hole was drilled to 130 feet below the Pittsburgh coalbed, a depth of 900 feet, and 880 feet of 7-inch-od casing was cemented in place. Seven vertical holes for monitoring the extent and progress of degasification have been drilled within the horizontal drilling area.