Drilling Long Horizontal Coalbed Methane Drainage Holes from a Directional Surface Borehole.
SPE/DOE Symp on Unconventional Gas Recovery Pittsburgh, Pennsylvania, 5/80 SPE Preprint 8968 PP 341-346 :341-346
Three primary horizontal methane drainage holes totaling 2,428.4 Meters (7,967 feet) have been completed in the Pittsburgh coalbed from a directional surface borehole. Directional control and sidetracking techniques developed during the project increased the horizontal drilling rate from 24.4 Meters (80 feet) per day initially to 64.9 Meters (213 feet) per day on the third horizontal hole. Drilling data indicate that horizontal holes can be drilled substantially longer than the maximum 977 meters (3,207 feet) achieved.
SPE/DOE Symp. on Unconventional Gas Recovery, Pgh., Pennsylvania, 5/80, Spe Preprint 8968, PP. 341-346