Deep Cooling Response to Injection in The Southeast Geysers

Abstract

Recent injection tracer tests and deep production well temperature logging have been analyzed to assess injectionrelated cooling in the southeast Geysers reservoir. Tracer tests conducted since 1997, when the Southeast Geysers Effluent Pipeline (SEGEP) began delivering supplemental water for injection, have shown a trend toward lower and slower recovery of injected tracer in produced steam. This trend continues in two recent tracer tests which indicate injection boiling efficiency is poor, resulting in diminished production of injection derived steam (IDS). Temperature logs in two steam production wells show deep temperature reversals, as much as 135°F of reservoir cooling, and a standing water column in one of the wells at a depth of 7,360 feet. These results have led to targeting of hotter, drier portions of the reservoir for diversion of SEGEP water deliveries. Future injection strategies for the southeast Geysers may include shallow, low rate injection wells to target the hot reservoir that remains above cooled zones.