Correction of non-equilibrated temperature logs and implications for geothermal investigations

Abstract

Optimum data for any geothermal investigation are densely sampled, high precision temperature logs from boreholes. They should represent the formation temperature as accurately as possible. Often, temperature measurements influenced by the drilling process and the circulation do not have the quality which is required for geothermal methods. Horner's method is a widely used correction method that is based on analysis of a time series of temperature observations. Mostly, these data are not available and a correction is therefore not possible. The approach presented here enables us to correct entire temperature logs even if no repeat measurements were carried out. This is achieved by combination of the theory of Horner's method with estimates for radial heat flow. Given a large number of technically perturbed logs this new approach enlarges considerably the potential database suitable for geothermal methods. The implications for two important fields of application are also discussed. These are fluid flow analysis and analysis of the ground surface temperature history on temperature logs. © 2005 Nanjing Institute of Geophysical Prospecting.