An Overview of High Energy Stimulation Techniques for Geothermal Applications

Abstract

Enhanced or engineered geothermal systems (EGS) require and effective method of generating a high surface area network of fractures, or the stimulation of existing fractures, in a formation in order to increase permeability/heat-transfer. Conventional hydraulic fracturing has limited utility in this application. Sandia National Laboratories is exploring high rate pressurization techniques employing tailored energetic materials systems to control both pressure rise rate and peak pressure in order to optimally stimulate potential geothermal formations. Rapid pressurization at rates, far exceeding quasi-static conventional hydraulic rates, can generate multiple radial wellbore fractures and potentially provide a mechanism to induce shear destabilization within the formation that enables the fractures to be self-propping. Multiple fractures from the wellbore allow efficient coupling to the existing formation fracture network. Furthermore, these techniques allow for repeated stimulations allowing fractures to be extended further. Controlled rate pressurization is a useful tool for the efficient implementation of EGS. This paper provides an overview of the concept of controlled rate pressurization, laboratory experiments and field trials that are being conducted. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.