Potential Advantages to Water Jet Drilling for Use in In-Situ Coal Gasification Processes

Abstract

Current methods of in-situ gasification require that inter-well connection be by means of either reverse combustion burning or by directional drilling. High-pressure water jet drills concentrate the energy of cutting in a small area and the total thrust required to advance this system is thus minimized. This has been used advantageously to develop a drill for coal seams which can be lowered down a vertical well turned through a 90-deg angle and then advanced horizontally through the coal. A test unit operating at a pressure of 70 MPa and a flow rate of 90 L/min has been used to demonstrate, in a surface trial, the practicality of this concept for interconnecting two in-situ gasification wells located 20 m apart.