| Title | Phase II Play Fairway Analysis Activities for Structurally-Controlled Geothermal Systems in the Eastern Great Basin Extensional Regime, Utah, USA |
|---|---|
| Authors | Philip WANNAMAKER, Kristine PANKOW, Joseph MOORE, Gregory NASH, Virginie MARIS, Stuart SIMMONS, Christian HARDWICK, and Rick ALLIS |
| Year | 2017 |
| Conference | Stanford Geothermal Workshop |
| Keywords | play fairway analysis, eastern Great Basin, exploration, GIS |
| Abstract | Our research team is carrying out a play fairway analysis (PFA) for geothermal resources in the Eastern Great Basin extensional tectonic regime of western Utah. Here, active Basin and Range (B&R) extension with volcanism having a N-S strike is superimposed upon pre-existing E-W belts of plutonic rocks and large-scale structural lineaments. This PFA aims to illuminate the potential sources of heat and permeability in the region, which are the two principal criteria for establishing a geothermal resource. Initial (Phase I) play fairway analysis (PFA) integrated several favorability indicators to define focus areas for Phase II followup that is intended to develop thermal gradient drilling targets. Criteria selected for establishing heat potential include direct heat flow measurements, MT low resistivity, seismicity swarms, fluid geochemistry, and proximity to recent volcanism. In particular, high-temperature systems commonly appear to connect via steep, low-resistivity crustal fault systems to deeper magmatic sources. Under Phase II support, new MT surveying is concentrated around Crater Knoll and Twin Peaks, and provides near continuous denser coverage westward from Cove Fort. Coarse MT site coverage extended south past the Roosevelt Hot Springs producing area. A geothermal fluid origin for low resistivity MT upwelling structures is being tested using Nodal passive seismic surveying that seeks presence of seismic swarms. New structural analysis in the area will exploit Google high-resolution DEM data that has become available for the state of Utah. Gravity fill-in is being accomplished to improve resolution of possible cryptic subsurface structures. Approximately 160 thermal gradient wells, 8 deep wells and 20 water wells with thermal information are being analysed and show a cumulative heat loss west and north of Cove Fort exceeding 100 MW, approximately twice that of the Roosevelt Hot Springs producing system. Promising geophysical and geological structures will be profiled for magmatic source input using new passive 3He detectors developed at the University of Utah. |