Development of a Cornering Water Jet Drill

摘要

Sandia National Laboratories is developing a drilling system which uses high velocity water jets to make horizontal holes in a coal seam accessed through a vertical borehole. For underground coal gasification (UCG), these horizontal holes can be drilled to create linking paths between vertical process wells. During shake-down tests in Albuquerque, five holes were drilled in a simulated coal seam. The 8 to 12 inch (20 to 30 cm) diameter holes deviated from their intended trajectories by less than 12 inches in 20 ft (6.1 m). Similar results have been produced during more recent field tests in an open pit coal mine. An exposed coal seam with undisturbed overburden was penetrated to a depth of 72 ft (21.9 m) with maximum deviations of less than four inches (10.2 cm) vertically and six degrees horizontally. A final proof-of-concept test, in which the seam was accessed from the surface through a vertical borehole, yielded a horizontal hole 50 ft (15.2 m) long with a maximum vertical deviation of +-5 inches (12.7 cm). For all tests to date, the on board logging instrumentation has provided accurate guidance and hole location data. Test results indicate that the drilling system is capable of producing horizontal holes for UCG applications. 11 references, 14 figures. (ERA citation 09:039286)