The Momotombo Reservoir Performance upon 25 Years of Exploitation

Abstract

The Momotombo geothermal reservoir has been developed for more than twenty years since 1983 when the first unit of 35 MWe commissioned. And the second unit was installed in 1989 by increasing steam production rate. During this period, production wells show marked changes in flow rates, fluid chemistry and specific enthalpies of produced fluids. These changes are mainly attributed to reservoir pressure decline because of excessive fluid production. By 1999, where the power plant output dropped to 9 MWe an international tender was issued for the rehabilitation of the project under a 15 year Concession. Ormat won the tender and undertook to drill additional wells, implementing a full reinjection and installing a bottoming OEC unit. Since then the plant is producing between 30 and 35 MWe supported by an intensive well maintenance program. Ormat’s investment stands at about US$ 45 Million, producing electricity at less than US$5.22 Cents/ kWh, making the Momotombo plant the lowest cost electricity producer in Nicaragua.