Beyond the EGS Protocol, A best practices document

One of the main issues often associated with subsurface fluid injection, an integral part of all the EGS technologies, is the impact as well as the utility of microseismicity (microearthquakes) that often occurs during the various stages of fluid injections. Although the Protocols are being used and followed by a number of geothermal stakeholders, the USDOE felt a "Best Practices" document was needed that would be used mainly by the geothermal operators and as a guideline for regulators. The "Best Practices" provides more detail than the Protocols, while still following the seven main steps in the updated Protocol (Majer et al., 2012). Like the Protocol, this Best Practices document is intended to be a living document; it is intended to supplement the existing IEA Protocol and the new DOE Protocol, and as practically as possible, be kept up-to-date with state-of-the-art knowledge and practices, both technical and non-technical. As methods, experience, knowledge, and regulations change with respect to induced seismicity, so should this document. It also recognizes that "one size" does not fit every geothermal project, and not everything presented should be required for every EGS project. Local conditions at each site will call for different types of action. Variations in procedures will result from such factors as the population density around the project, past seismicity in the area, the size of the project, the depth and amount of injection and its relation to any geologic faults, and others. Described will be several different approached that may be taken to successfully deal with induced seismicity and the status of the state of the practice as well experiences with regulators and the operators.