The lithology and structural features of the Ahuachapa??n geothermal area and their impact on the movement of cold and hot fluids within the system are described, as well as the development and evaluation of the natural state model of the field. Four major lithologic units are present in Ahuachapa??n and three major aquifers have been identified; flow patterns and zones of fluid mixing were located on the basis of temperature and geochemical data from wells and surface manifestations. Geologic structures control the heat and fluid recharge and the flow within the reservoir. Modeling studies suggest, in agreement with field data, an overall average transmissivity of 25-35 darcy-meters, and indicate that the system is recharged by waters with temperatures greater than 250??C. The total thermal throughflow for the Ahuachapa??n reservoir in the unexploited state is estimated to be about 250 MWt. ?? 1991.
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Pre-exploitation state of the ahuachapa??n geothermal field, el salvador