Structure, Permeability and Production Characteristics of the Heber, California Geothermal Field

The three key permeability elements of the Heber reservoir are “capping” clays above 1800', a sedimentary “matrix permeability” reservoir from 1800'-5500', and fracture permeability in indurated sediments below 5500'. The fractures are related to NW trending strike-slip faults and NE trending normal faults. Maps and cross sections with dipmeter, lost circulation, temperature and Kh data illustrate the structures and their control on the movement of thermal waters. Production creates a strong initial pressure decline in the field that rapidly stabilizes. The long-term pressure decline is predicted to be low (less than 5%). Temperature data show that current development is north of the source of the thermal plume. Reservoir modeling indicates that reservoir pressures will support further development. 14 figs., 2 refs.