Coso Geothermal Field Conceptual Model Update

The Navy Geothermal Program (GPO) has focused geoscience efforts on the Coso geothermal field (“Coso”) in recent years and is now building a conceptual geologic model of the field using Leapfrog software. New data sets collected over the past two years augment decades of geological, geophysical and drilling logs and include LiDAR, microgravity and two phases of 2 meter probe data. LiDAR data in and around Coso were collected after the Ridgecrest earthquake sequence of July 4-5, 2019. When differentiated from a 2017 LiDAR data set, results may reveal ground disturbances not observed during feed inspections immediately after the earthquakes, especially along known and possibly unknown Quaternary faults. Over the last 30 years, Coso has been subjected to seismicity as well as a tremendous loss of mass associated with dual flash production from this 270 MWe installed capacity operation. In addition to building a 3D model of the geothermal field in order to better inform future production and research-related work, the objectives of this work include quantifying changes to better understand how Coso has evolved over time. Minimally, changes observed include an expanded steam cap, shallow density changes associated with mass removal, concomitant pressure changes and local subsidence as well as tumescence that may be associated with production and tectonism. Like the existing reservoir model, this 3D conceptual geological model will be a living entity and will evolve as additional data are added over time.