Abstract: Geology and Development of Momotombo Geothermal Field, Nicaragua

James L. Moore, Jr., Paul V. Storm, Carlos Ferrey, Erik Osbun

Geologic parameters influence the development of over 2 × 10⁶ lb/hour of separated steam (100 Mw) from the Momotombo geothermal field. The Momotombo geothermal field is approximately 50 km northeast of the city of Managua on the southern flanks of Volcan Momotombo and on the northeastern shore of Lake Managua. Geologically, this places the field on the western margin of the Nicaraguan depression and within the belt of active Central American volcanoes.

Surface and near-surface rocks consist of intermediate to basic ash fall and ash-flow tuffs, containing scattered flows of basalt. Subsurface rocks consist primarily of tuffs of intermediate composition. The degree of rock alteration is extremely variable, both horizontally and vertically. Production appears to be related almost exclusively to fractures.

Development drilling has established the existence of at least two distinct producing fracture zones. One of these zones shows definite and pronounced temperature reversal below production; the other shows a continued increase of temperature with depth. The average production temperature is approximately 225°C. Wells with mass flow potentials greater than 10⁶ lb/hour are common.

AAPG Search and Discovery Article #90962©1978 AAPG 2nd Circum-Pacific Energy and Minerals Resource Conference, Honolulu, Hawaii