Abstract: Geology and Reservoir Analysis of East Mesa Geothermal Field, Imperial County, California

Walter H. Ortel

The East Mesa geothermal field in Imperial County, California, 18 mi (29 km) east of El Centro, was discovered in the summer of 1972. Recent drilling indicates a productive area--with temperature above 350°F (177°C) and at a depth less than 7,000 ft (2,134 m)--of approximately 3,600 acres (1,457 ha.). Two distinguishable formations, separated by an unconformity, have been drilled at East Mesa. The upper formation has been correlated with the Brawley of Pleistocene age, whereas the lower group is correlated with the Palm Springs of Pleistocene-Pliocene age. Most of the geothermal fluids will be produced from this lower interval which consists of sandstones and thin shales deposited in the Colorado River delta. Structurally, the field is located on a broad anticli al nose which plunges into the Salton trough. The anticlinal feature is modified by faults cutting transversely across the fold. These faults are associated with the San Andreas system which trends northwest-southeast, paralleling the Imperial Valley.

Currently, the field is in the early stages of testing and evaluation. Bulk reservoir volume was computed to give the initial water and energy in place above a depth of 7,000 ft (2,134 m) and at temperatures greater than 350°F (177°C). Recovery factors depend on production rates, pressure maintenance, and reservoir geology. Simulation studies show pressure and temperature changes under various production rates and the need for injection to maintain adequate pressure and prevent excessive drawdowns.

AAPG Search and Discovery Article #90969©1977 AAPG-SEPM Rocky Mountain Sections Meeting, Denver, Colorado