Geologic and Reservoir Model of the Maibarara Geothermal Field

Abstract

Hydrothermal alteration and fluid inclusion data were used to help develop the geologic reservoir conceptual model of the field. This conceptual model the basis for an on-going reservoir simulation study. Within the 2.5 proven production area, there is a good correlation between both fluid inclusion temperature and alteration mineralogy with measured wellbore temperatures, while outside this the correlation is poor. South of the central benign chloride reservoir, acidic fluids occur along discrete stratigraphic zones, by the presence of pyrophyllite. On the northern margin of the field. considerable cooling has occurred due to incursion of cooler shallow fluids. A comparison of the past (evidenced by fluid inclusions and alteration mineralogy) with the present (measured) temperatures shows that the reservoir contracted, margins have cooled by at least 60?C over time. The presence of marginal cooler acidic fluids limits the potential development size of the resource. The installation of an 11 power plant is under considention by the National Power Corporation.