Near-Field EGS: A Review and Comparison of the EGS Demonstration Projects at Desert Peak and Brady

Abstract

Two US Department of Energy (DOE) Geothermal Technologies Office (GTO) Enhanced Geothermal Systems (EGS) demonstration project grants were awarded to Ormat Nevada, Inc. to evaluate the feasibility of EGS development in the Basin and Range geomorphic province. These projects focused on stimulating a non-commercial well on the periphery of the operating conventional geothermal system with the goal to evaluate characterization tools and methodologies, stimulation technologies, and ultimately improve the permeability enough to connect the well to the existing power plant. The first of these projects, Desert Peak, formed a stimulation road map that was followed at the second project, Brady. These steps included detailing the lithologies and ambient stress field, developing a robust microseismic monitoring network, pre-stimulation permeability testing, implementing zonal isolation, and finally designing the optimal stimulation plan. Following the successful result of a 1.7 MW increase at the Desert Peak facility with new injection to the stimulated well 27-15, the stimulation at Brady 15-12 resulted in lower than expected permeability increase. Each project, though with differing levels of success, have contributed tools, techniques, and analysis that will inform EGS projects going forward, including the FORGE project at Milford, Utah. Lessons can be learned from reviewing the types of data collected prior to the stimulation activities, the stimulation plan, and exploring why the results at Brady were different from those at Desert Peak.