GEOTHERMAL FAVORABILITY MODEL OF WASHINGTON STATE

In the early phases of geothermal exploration, many important geological details are unknown. A regional exploration model (play-fairway analysis) based on available data and exploratory principles can identify areas where it would be most beneficial to obtain more detailed data.

In 2011, the U.S. Department of Energy funded a three-year effort by state geological surveys to compile and collect all varieties of new and existing geothermal-related data and information for inclusion in the National Geothermal Data System. In support of this effort, the Washington State Department of Natural Resources Division of Geology and Earth Resources, developed and (or) revised numerous datasets of existing geothermal and geological data in WA State. Using this newly compiled and collected data, a Geographic Information System (GIS)-based analysis of relevant spatial datasets was used to determine the spatial association between various geologic and thermal features, infrastructure, and land-use to gain a broad understanding of geothermal resource potential and favorability for development in WA State.

The geothermal favorability model of WA State was constructed by performing multiple iterative ArcGIS processes on volcanic vent, young silicic intrusive rock body, thermal spring, borehole temperature gradient, fault, earthquake, electric transmission line, and elevation datasets.

The model shows relatively high favorability in localized areas of the Columbia Basin as well as areas within the South Cascades. The model also illustrates the challenges of developing geothermal resources in WA State—most areas of the state with potential resources are remote, with little infrastructure or accessibility. Proximity to transmission lines and elevation and land-use restrictions significantly impact geothermal favorability, rendering potential resource areas unfavorable for exploration and (or) development, including most of the thermal areas along the crest of the Cascade Range. However, the potential for local, small-scale geothermal power production remains an option for some remote locations.

The modeling incorporates the most complete and accurate data compilations to date, but is nevertheless limited by the quantity, quality, and sparse or irregular distribution of available data.