| Authors |
John W. SHERVAIS, Jonathan M. GLEN, Dennis NIELSON, Sabodh GARG, Patrick DOBSON, Erika GASPERIKOVA, Eric SONNENTHAL, Charles VISSER, Lee M. LIBERTY, Jacob DEANGELO, Drew SILER, James P. EVANS |
| Abstract |
The Snake River Plain (SRP) volcanic province overlies the Yellowstone hotspot, a thermal anomaly that extends deep into the mantle. The SRP is one of the highest heat flow provinces in North America, which has been estimated by the USGS to host up to 855 MW of potential geothermal power production. Our goals for the study were to: (1) adapt the methodology of Play Fairway Analysis for geothermal exploration to create a formal basis for its application to geothermal systems, (2) assemble relevant data for the SRP from publicly available and private sources, and (3) build a geothermal play fairway model for the SRP and identify the most promising plays, using GIS-based software tools that are standard in the petroleum industry. Most of the study area is underlain by a basaltic volcanic province that overlies a mid-crustal intrusive complex, which in turn provides the long-term heat flux needed to sustain geothermal systems. This represents a new conceptual model for geothermal systems that includes aspects of volcano-hosted systems and structurally controlled Basin-and-Range systems. This study focused on three critical parameters for exploitable hydrothermal systems: Heat source, reservoir and recharge Permeability, and cap or Seal. Data included in the compilation for Heat were heat flow, the distribution and ages of volcanic vents, groundwater temperatures, thermal springs and wells, helium isotope anomalies, and reservoir temperatures estimated using geothermometry. Permeability was derived from analysis of stress orientations and magnitudes, post-Miocene faults, and structural lineaments based on maximum horizontal gradients in magnetic and gravity surveys. Data for Seal included the distribution of impermeable lake sediments and clay-seal associated with hydrothermal alteration below the regional aquifer. These data were used to compile Common Risk Segment (CRS) maps for Heat, Permeability and Seal, which were combined to create a Composite Common Risk Segment (CCRS) map for all of southern Idaho. Our Phase 1 assessment suggests that important undiscovered geothermal resources may be located in several areas of the SRP. Our results identify eight areas with multiple prospects, each of which may contain resources that equal or exceed the 10 MWe Raft River geothermal plant. Four of these areas are in the Western Snake River Plain (WSRP) and include blind systems; two are in the Central Snake River Plain (CSRP), and two are Basin-and-Range play types in eastern and southeastern Idaho. Our training site in the WSRP (on Mountain Home Air Force Base) is a blind resource similar in temperature to Raft River. Our identified prospects exhibit higher favorability on CRS and CCRS maps than either of our training sites (Mountain Home, Raft River), and have regional extents that generally exceed both of our training sites. |