The role of thermal conduction from confining beds in the thermal recharge of low-enthalpy geothermal reservoirs

Abstract

This paper presents a conceptual study of the role of the conductive heat transfer from the confining beds into a series of low-enthalpy, geothermal reservoirs during energy production from a doublet well system. The results clearly demonstrate the significant role of the thermal conductivity of adjacent formations in the thermal recharge of the reservoir. For a specific example, increasing the matrix thermal conductivity of the confining beds from 1.5 W/m/K to 4.5 W/m/K reduces the decline in production temperature by 35% and increases the conductive warming of the reservoir, relative to total extracted energy, by 34% after 300 years of production. The different cases furthermore exhibit large differences in the penetration of the thermal disturbance into the confining beds. Accurate delineation and model representation of the thermal properties of the confining beds are necessary in order to make reliable estimates of thermal resources and long-term projections of production temperatures.