Heat Extracted from the Long Term Flow Test in the Fenton Hill HDR Reservoir

Abstract

A long-term flow test was carried out in the Fenton Hill HDR Phase-2 reservoir for 14 months during 1992-1993 to examine the potential for supplying thermal energy at a sustained rate as a commercial demonstration of HDR technology. The test was accomplished in several segments with changes in mean flowrate due to pumping conditions. Re-test estimates of the extractable heat content above a minimum useful temperature were based on physical evidence of the size of the Fenton Hill reservoir. A numerical model was used to estimate the extent of heat extracted during the individual flow segments from the database of measured production data during the test. For a reservoir volume of 6.5~106 m3, the total heat content above a minimum temperature of 150" C was 1.5~10'~ J. For the total test period at the three sustained mean flowrates, the integrated heat extracted was 0.088~10'~ J, with no discernable temperature decline of the produced fluid. The fraction of energy extracted above the abandonment temperature was 5.9 %. On the basis of a constant thermal energy extraction rate, the lifetime of the reservoir (without reservoir growth) to the abandonment temperature would be 13.3 years, in good agreement with the pre-test estimate of 15.0 years for the given reservoir volume.