Research Report of Low Temperature Geothermal Play Fairway Analysis for the Appalachian Basin

This is a final report summarizing a one-year (2014-15) DOE funded Geothermal Play Fairway Analysis of the Low-Temperature resources of the Appalachian Basin of New York, Pennsylvania and West Virginia. Collaborators included Cornell University, Southern Methodist University, and West Virginia University. As a result of the research, 'play fairways' were identified for further study, based on four 'risk' criteria: 1) the Thermal Resource Quality, 2) the Natural Reservoir Quality, 3) the Risk of Seismic Activity, and the 4) Utilization Viability.

In addition to the final report document, this submission includes project 'memos' referred to throughout the report. Many of these same memos are also provided in the submission with the detailed data products accompanying the relevant risk factor (thermal, reservoir, seismicity, and utilization).

A portion of the executive overview follows:

Geothermal energy is an attractive sustainable energy source. Project developers need confirmation of the resource base to warrant their time and financial resources. The hydrocarbon industry has addressed exploration and development complexities through use of a technique referred to as Play Fairway Analysis (PFA). The PFA technique assigns risk metrics that communicate the favorability of potential hydrocarbon bearing reservoirs in order to enable prudent allocation of exploration and development resources.

The purpose of this Department of Energy funded effort is to apply the PFA approach to geothermal exploration and development, thus providing a technique for Geothermal Play Fairway Analysis (GPFA). This project focuses on four risk factors of concern for direct-use geothermal plays in the Appalachian Basin (AB) portions of New York, Pennsylvania, and West Virginia (Figure 1). These risk factors are 1) thermal resource quality, 2) natural reservoir quality, 3) induced seismicity, and 4) utilization opportunities (Figure 2). This research expands upon and updates methodologies used in previous assessments of the potential for geothermal fields and utilization in the Appalachian Basin, and also introduces novel approaches and metrics for quantification of geothermal reservoir productivity in sedimentary basins. Unique to this project are several methodologies for combining the risk factors into a single commensurate objective that communicates the estimated overall favorability of geothermal development. Uncertainty in the risk estimation is also quantified. Based on these metrics, geothermal plays in the Appalachian Basin were identified as potentially viable for a variety of direct-use-heat applications. The methodologies developed in this project may be applied in other sedimentary basins as a foundation for low temperature (50-150 degC), direct use geothermal resource, risk, and uncertainty assessment. Through our identification of plays, this project reveals the potential for widespread assessment of low-temperature geothermal energy from sedimentary basins as an alternative to current heating sources that are unsustainable.

There is an important distinction in this Geothermal Play Fairway Analysis project as compared to hydrothermal projects: this Appalachian Basin analysis is focused on the direct use of the heat, rather than on electrical production. Lindal (1973) illuminated numerous industrial and other low-temperature applications of geothermal energy for which this analysis can be useful. The major relationship to electricity is that direct-use applications reduce the electricity requirements for a region. Even though all of the geothermal resources in the Appalachian Basin are low grade, the high population and high heating demand across New York, Pennsylvania, and West Virginia translate into economic advantages if geothermal direct-use heating replaces electricity-based heating. The advantage is derived from the high efficiency of extracting heat from geothermal fluids rather than converting the fluids to electricity (Tester et al., 2015).