A Modeling Study of the Natural State of the Heber Geothermal Field, California

Abstract

As a first step in simulating the behavior of the Heber field under exploitation, the system is modeled in its natural (pre-exploitation) state. Using Lawrence Berkeley's Laboratory's, (LBL) computer code PT and a radically symmetric model, a reasonable match between published and calculated temperature and pressure distribution is obtained. The results of the study indicated that the Heber geothermal system is created by the up flow of hot water through a central zone of higher permeability. The model shows that in its natural state the system is recharged at a depth by a 15 MW (thermal) convective heat source. The existence of a radially symmetric convection pattern, whose axis coincides with that of the Heber anomaly is suggested. At the lower part of the ascending hot water plume, the deep recharge water mixes with colder water moving laterally towards the axis of the system. On the upper part, the rising plume spreads radially outward before reaching the bottom of the caprock, at 550 m depth. The model results suggest that the caprock is quite permeable, with convection controlling the temperature distribution. The low permeability of the upper zones in the out region of the system may be due to mineral precipitation.