Evidence for Deep-Flowing Cool Recharge Solutions at the NE Part of the Coso Geothermal Field from Clay Minerals and Fluid Inclusion Gas Analysis

摘要

Wells 58A-10 and 76-27 drilled northeast of the Coso geothermal reservoir were studied by clay mineral analysis and fluid inclusion gas chemistry. These analyses indicate the common presence of low temperature meteoric fluids. Kaolin is a common alteration mineral in both wells. Reaction modeling of kaolin formation indicates this best occurs by action of solutions of 100 deg C or less and requires water/rock ratios of 60 or more. A remarkable change in fluid inclusion gas chemistry at 6200 ft in well 58A-10 indicates the presence of a seal at that depth. The fluid inclusion, gas, and clay data are consistent with the area of wells 76-27 and well 58A-10 providing recharge fluid to the Coso system and with Coso being a prograding geothermal system. The highest concentration of kaolin occurs at depths thought to be fracture zones.