Integrating geophysical data in GIS for geothermal power prospecting

Abstract

Geographic information system (GIS)–based resource assessment is an important and relatively inexpensive tool for identifying areas that are of interest for geothermal power production. Of particular interest is the under-exploited industry of co-produced fluids and low-temperature formation waters in oil- and gas-producing basins. Obtaining bottom-hole temperature (BHT) data is now free and easily accessible due to the efforts of the National Geothermal Data System (NGDS). Oil- and gas-producing sedimentary basins in Colorado, Illinois, Michigan, and North Dakota contain formation waters of a temperature that is adequate for geothermal power production (90–150 °C) using existing binary power plant technology. While resource assessment gives a broad picture of the energy available in a basin, the problem remains of knowing where a power plant must go, and if it is economically feasible to do so in any given area. The Denver, Illinois, Michigan, and Williston sedimentary basins were evaluated using a play fairway analysis methodology to identify optimum locations for geothermal power production. These regions have been previously assessed for thermal energy in place, and geothermal gradients from that study, along with gravity anomaly information, magnetic intensity, and digital elevation models (DEMs) for slope analysis were incorporated into a geodatabase for map generation. Raster layers were created and then reclassified into nine classes each, with high geothermal gradient, low magnetic intensity, low Bouger anomaly, and low slope receiving the highest values. The layers were then weighted using a matrix weight assignment similar to that used in the Environmental Protection Agency’s DRASTIC water pollution model, and combined with the “Raster Algebra” tool in ArcGIS. Areas of greatest potential were identified and overlaid on a DEM layer. This shows locations where temperature will be highest at the shallowest depths in regions of soft sediments, refining the map creation process.