San Jacinto-Tizate geothermal field,Nicaragua: Exploration and conceptual model

The results of the exploration of the San Jacinto-Tizate geothermal field during 1992–1995 included geological, hydrogeological and geophysical investigations (magnetotelluric, frequency soundings, subsurface temperature, and soil-gas surveys), and the drilling and testing of seven deep wells (728–2339 m). The geothermal field, located within a composite volcano-tectonic depression, can be divided into two main areas: San Jacinto and Tizate. The San Jacinto area shows evidence of a high-temperature (250–300°C) fossil geothermal system that at present has reservoir temperatures in the 180–190°C range. In the Tizate area there is an active geothermal system with temperatures of 250–285°C. An upflow zone with an excess pressure gradient exists in the central part of this area. Two hydraulically connected reservoirs exist: a shallow one at 550–1200 m depth, and a deeper one below 1600m. Two-phase conditions exist in the upper part of the shallow reservoir. Production tests demonstrate the commercial potential of both Tizate reservoirs.