| Title | East Mesa Geothermal Anomaly, Imperial County, California: Significance of Temperatures in a Deep Drill Hole Near Thermal Equilibrium |
|---|---|
| Authors | Urban, T. C.; Diment, W. H.; Nathenson, Manuel |
| Year | 1978 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Exploration; Drilling; USA; California; Imperial; East Mesa; USGS |
| Abstract | Precision temperature logs were obtained in U.S. Bureau of Reclamation drill hole Mesa 31-1 at East Mesa to a depth of 1880 m. Comparison of logs taken some two months apart and nearly a year after the production testing suggests the hole is close to thermal equilibrium. The thermal regime of the hole is characterized (1) by high gradients which predominate in the conductive cap (0-840m) and area affected by hydrologic disturbances to at least 150 m, (2) by a sharp decrease in gradient at the base of the cap ( approx. 840 m), (3) by a uniformly low gradient (40°C/km) below the cap except near the perforated zones (below 1650 m), and (4) by small convective motions within the hole as indicated by temperature time recordings. The observed low gradient below the cap does not necessarily imply convection in a thick permeable medium. Instead, simple numerical models suggest the gradient could be the result of conductive heating from a hot permeable zone maintained by horizontal water movement near the base of the cap. |