Numerical Modelling of the Momotombo Geothermal Reservoir, Nicaragua

Abstract

The Momotombo geothermal field is located on the northwestern shore of Lake Managua and on the southwestern slope of the active Momotombo Volcano, Nicaragua. The field has been producing steam since 1983 and has an installed capacity of 77 MWe with 47 wells drilled in an area of 2 km2. There are three permeable layers at Momotombo: a shallow layer can be found between 200 and 700 m b.s.l., the other two are located at 700 to 1500 m b.s.l., and 1500 to 2000 m b.s.l.. The hydrogeological model of the reservoir indicates that a major upflow related to NE-SW trending faults presents below the western part of the well field. The producing wells in the eastern half of the field are fed by shallow lateral flow from the major upflow. Temperature profiles of shallow wells in the eastern part support a presence of an inflow of low temperature fluid from the southeastern part of the well field and below the shallow reservoir of high temperature. Three-dimensional numerical model consisting of 1863 grid blocks was developed for reservoir simulations, and then natural state simulation of Momotombo, production and injection simulations for more than 20 years of exploitation were carried out with this model using AUTOUGH2 and iTOUGH2 simulators.