Earth Sciences Division (ESD) Department of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL)

Energy Resources Program Project: Integrated Chemical Geothermometry System for Geothermal Exploration

Nicolas Spycher, Mack Kennedy, Eric Sonnenthal

Integrated Chemical Geothermometry System for Geothermal Exploration

The objective of this project is to develop a practical and reliable system to predict geothermal reservoir temperatures from full and integrated chemical analyses of spring and shallow well fluids.  We will apply advanced geochemical and reactive transport modeling tools (e.g., Toughreact, Xu et al., 2006; chiller/solveq, Reed 1982, 1998) to identify and see through near surface processes, such as dilution, gas loss, etc., that mask or hide the chemical signatures of deep reservoir temperatures in near surface fluids.  We will build on the method developed previously for single point sources by Reed and Spycher (1984) and later expanded by Peng and Reed (1998).  This method relies on computed saturation indices of multiple minerals, and is a significant improvement over classical geothermometers (Si, Fournier and Rowe, 1966; Na-K-Ca, Fournier and Truesdell, 1973) in that the full chemical analysis of the water is considered. The method will also build on advances in reactive transport modeling carried out at LBNL to integrate effects of water-rock interactions affecting reservoir fluids, including mineral dissolution/precipitation kinetics, as they ascend to sampling points.  This integrated approach, relying on multicomponent geochemical computations for multiple water samples, combined with sophisticated optimization methods, should allow for estimations of reservoir temperatures with much better reliability and consistency than are currently possible using standard geothermometers.