Experimental verification of the load-following potential of a Hot Dry Rock geothermal reservoir

A recent 6-day flow experiment conducted at the Los Alamos National Laboratory's Fenton Hill Hot Dry Rock (HDR) test site in north-central New Mexico has verified that an HDR reservoir has the capability for a significant, and very rapid, increase in power output upon demand. The objective of this cyclic load-following experiment was to investigate the performance of the reservoir in a nominal high-backpressure (2200 psi) baseload operating condition upon which was superimposed greatly increased power production for a 4-hour period each day. In practice, this enhanced production was accomplished by dropping the production well backpressure from the preexisting level of 2200 psi down to about 500 psi to rapidly drain the fluid stored in the pressure-dilated joints surrounding the production well. During the last cycle of this six-cycle test, the mean production conditions were 146.6 gpm for 4 hours at a temperature of 189°C followed by 92.4 gpm for 20 hours at a temperature of 183°C. These flow and temperature values indicate a flow enhancement of 59%, and a power enhancement of 65% during the high-production period. The time required to increase the reservoir power output from the baseload to the peaking rate was about 2 minutes