Geothermal Energy Resource Investigations, Chocolate Mountains Aerial Gunnery Range, Imperial Valley, California

摘要

The US Navy's Geothermal Program Office (GPO) has conducted geothermal exploration in the Chocolate Mountains Aerial Gunnery Range (CMAGR) since the mid-1970s. At this time, the focus of the GPO had been on the area to the east of the Hot Mineral Spa KGRA, Glamis KGRA, and areas within the Chocolate Mountains themselves. We have used potential field geophysics, mercury surveys, and geologic mapping to identify potential anomalies related to recent hydrothermal activity. After a brief hiatus starting in the early 2000s, the past two years have seen an accelerated exploration schedule focusing on the potential extension of nearby geothermal fields and the discovery of new resources. Potential occurrence scenarios include both sedimentary-hosted (East Mesa-type) and fault-controlled bedrock geothermal resources lying beneath the broad alluvial slope within the boundaries of the CMAGR. We have established three exploration areas, generally termed Hot Mineral Spa/Camp Billy Machen, East Niland, and Glamis, with exploration efforts currently focused on the Hot Mineral Spa/Camp Billy Machen (CBM) area. Recent exploration includes a high resolution aerial lidar survey flown over the project areas, securing over 177,000 square kilometers of <30cm accuracy digital elevation data. Lidar data were analyzed to characterize the active tectonic environment and identify Holocene structures, which are common conduits for up welling geothermal fluids. Gravity and ground-based magnetic surveys wereconducted during the summer of 2008. These data were acquired to aid in the identification of structures without fair surface expression, obscured by recent deposition. Shallow temperature gradient drilling began at the CMAGR in January of 2010. Thirteen temperature gradient holes were completed to a depth of 500' below ground surface. Sites were selected based on the compilation of previous exploration and resulting data are being integrated into the most recent geologic model. This model will form the basis for the selection of a deeper (2000'-4000') temperature gradient drilling campaign at the CMAGR in 2011.