Title: Analysis of wellbore temperatures and pressures in the Momotombo geothermal field, Nicaragua

Abstract

This report is a study of changes in temperature, pressure and cnthalpy in the Momotombo
high temperature geothermal field, Nicaragua, Central America. The downhole data considered
in this report was collected in 33 of the 39 wells in the field. A simple database was created
on a PC personal computer for storing and processing the data, which consisted of 522
downhole temperature measurements and 45 pressure measurements. The measurements were
carried out between 1975 and 1989. All these measurements are presented in supplementary
appendix B of this report. A study of the reservoir temperature history snOVlS that the
northeast part of the well field has cooled down at a rate of up to 6°C/year. Other parts of
the field remain unchanged or show a slight increase in temperature. Analysis of pressure data
shows a minimum drawdown rate of 0.3 bars/year in the well field, and much higher drawdown
rates in production wells. The production enthalpy of some wells that produce from shallow
levels in the Momotombo reselVoir, has changed from 1100 kJ/kg to almost a dry steam
enthalpy. indicating that production from the field has reached peak capacity in some areas.