Successful Deployment of a Multi-Crossing Directional Drilling Method at Ormat’s New Tungsten Mountain Geothermal Field in Churchill County, Nevada

Abstract

An innovative drilling method and successful drilling campaign is presented using an example from Ormat’s Tungsten Mountain Geothermal field in Edwards Creek Valley Nevada. Initial deep exploration drilling identified a ~285oF high-permeability resource along the eastern flank of the Clan Alpine Mountains near Stone Canyon. The resource is hosted within fractured and mineralized Mesozoic siltstone, slate, and intrusive formations. Permeability is focused within the damage zones of several synthetic steeply SE dipping NE-striking faults and partially along SSW dipping WNW-striking faults near their intersections with the NE-striking faults. However extreme variability of permeability discovered in the fault zones necessitated a drilling strategy that would reduce drilling risk and achieve successful wells. A 3D geological model was built and utilized to select the initial production well location and to guide directional drilling activities. The well was drilled using a super single drilling rig equipped with a top drive. Based on multiple geological targets generated from the 3D model, complex directional plans were generated. As new data were used to calibrate the 3D model and guide exploration and as directional drilling challenges arose, directional plans were revised and implemented during active drilling to achieve multiple intersections of a single fault zone.