Title: Initial temperature distribution in the Momotombo geothermal field, Nicaragua

Abstract

An analysis and interpretation is given of the initial temperature distribution in the Momotombo
high temperature field, Nicaragua. Central America. The study was based fundamentally on
more than 500 downhole temperature measurements and a mineralogical study of 1(3 of the
wells. A database was used to estimate initial and alteration temperatures in each well. Then
temperature cross and plane sections of the field were made which were analyzed for the
construction of a conceptual model for the reservoir. The geothennal field is divided into two
reservoirs. A hot deep upflow zone with a temperature range of 250-29<fC, which is located
in the western part of the field at > lCX>O m U,S.1. The deep reservoir feeds a shallow and
horizontal reservoir at 200-400 m u.s.l., which has a temperature range of 200-230°C. Both
reservoirs are liquid dominated. An equilibrium between alteration and initial temperature
seems to exist in most of the wells analyzed. However, in the southeastern part of the field
are signals of natural cooling, observed as inflow of < lOOOC water into the geothermal system.
The areal extent of the deep reservoir is unknown to north and west. Future drilling should
be directed to this part of the field as the geothermal reservoir has not yet been bounded by
drilling in these directions.