Rock Melting: a Specialty Drilling System for Improved Hole Stability in Geothermal Wells

Abstract

A Los Alamos National Laboratory team is actively reevaluating a drilling system that uses electrically-heated graphite, or molybdenum penetrators to melt a hole as it is slowly pushed through rock. The primary result of a rock melting penetrator is to form molten material that consolidates into a rugged glass lining, thus preventing hole collapse and minimizing the potential for cross-flow and lost circulation. Drilling fluid requirements are reduced or eliminated, and the penetrator does not rotate. Laboratory bench tests are being coupled with time-dependent thermomechanical models to understand the physics of the process and adapt rock melting to a variety of field environments. The potential geothermal drilling applications include a wellbore seal in lieu of intermediate casing particularly in areas of lost circulation or borehole wall collapse. Additionally, by modifying the penetrator tool, the system could be designed to melt through a stuck pipe or bit, thereby eliminating cementing and redrilling. Modification of the rock melting drill to allow injection of reagents and thinners into the melt to increase penetration rates, and enhance glass liner properties is also under investigation.