A PRACTICAL SOLUTION FOR THE TRANSIENT RADIAL-VERTICALHEAT CONDUCTION IN GEOTHERMAL WELLS

Abstract

When drilling geothermal wells the fluid exchanges thermal energy to the surrounding rock during its vertical ascent toward reservoir colder areas. This transmission of heat from the casing toward the formation in low permeability reservoirs is essentially conductive. The importance of its study is based on the fact that this loss of heat could have influence in the natural fluid thermodynamic conditions and in the prediction of its natural original state. There is even another reason: during drilling, the first thermal data contain valuable information about rock thermal parameters, essentially effective thermal conductivity and specific heat. The analysis of the anomalies or discontinuities in the transmission of heat provide indirect information about the extension and abundance of fractured areas. In this document we present an exact semi-analytic model for the numerical analysis of the transient heat conduction when the thermal energy flows simultaneously in radial and vertical directions. This model provides a practical solution of the type T (r, z, t) resulting of coupling two classic solutions in two independent dimensions. We introduce some applications to a geothermal well in a Mexican field.