A 3-D natural state modelling and reservoir assessment for the Berlin geothermal field in El Salvador, C.A.

Abstract

Twenty-five years have passed since geothermal research and drilling were activated in the Berlin geothermal field, El Salvador. In this report, a brief description is given on the surface exploration carried out in the area, and the six deeper wells drilled. Evaluation of formation temperatures and pressures are given. The results of these studies are unified into a single, conceptual model of the geothermal system. An upflow zone of 300 C is assumed underneath the Berlin caldera. The fluid flows laterally towards northeast into the present wellfield, where the flow changes direction towards the northnorthwest. The reservoir is of two layers, a shallow one of 200-230 C at sea level and a deep one of 270-290 C at -1000 m a.s.l. All of the reservoir volume seems to be in a single-phase, liquid condition. The deeper reservoir is productive. A study on interference data reveals permeabilities in the order of 50-100 mD. High storativity values are also evident. A wellbore simulation study indicates that the Berlin wells flash down to their feedzones, during production, and some distance into the reservoir. Enthalpy changes are, however, still negligible. The conceptual reservoir model and the production data were simulated in a 3-dimensional grid, using the TOUGH simulator. A satisfactory match was obtained for the measured and the calculated data. The high reservoir storativity was presumed to be due to a large volume of the single-phase liquid reservoir (60-80 km3) ...