Stored Heat Evaluation in Geothermal Systems: A Case of a Mexican Field

Aragon-Aguilar Alfonso, Izq

Abstract

México is rich in renewable energy sources (solar, wind, biomasss, hydropower and geothermal). Nevertheless, the potential of this type of energy has not been fully exploited. Geothermal energy in the country is one of the renewable energies used for electric generation although Hydropower is between renewable energy sources with the highest installed capacity. México ranks fourth, in the world, in installed electric capacity, from geothermal resources. In this work is presented a methodology for stored heat evaluation in the zone central eastern of Los Humeros geothermal field. The wells grouped in this section of the field are non producers, however in the neighboring zone (central western) are producers. We present an analysis, which shows an evolution, in producer wells from two phases toward one phase (steam) in its produced mass. It was determined temperatures distribution in this central zone using data of producers and non producer wells. Moreover, through using isothermal surfaces and establishing temperature bounds of 200, 250 and 300°C were determined net thicknesses in each well with possibility for heat storage. The innovative contribution of this work is focused to rescue non producer wells with high temperature although low permeability and scarce recharge. Considering different scenarios of reservoir properties in the studied zone were determined stored heat and its corresponding evaluation for obtaining electric generation. In determinations, values of specific heat (cT) between 1500 and 2900 [kJ/(m3°C)] and the reservoir temperature, 200°C < (TR) < 300°C, were used. The obtained results are expressed in MWTh and show the feasibility for extending the methodology to other similar fields. Through variation of extraction factor between 0.01 and 0.05, and efficiencies conversion of 0.10 and 0.25, energy in MWTh was determined. The methodology results are useful in taking decisions about feasibility of a project for heat extraction for its commercial exploitation.