Application of a spherical-radial heat transfer model to calculate geothermal gradients from measurements in deep boreholes

This paper presents estimates of the undisturbed formation temperatures in a geothermal exploration well drilled in the Ceboruco area in the western part of the Mexican Volcanic Belt. The method used assumes that during the warming-up period following fluid circulation, heat transfer from the surrounding formation to the wellbore is spherical-radial in the bottomhole region of the well. According to this model, the transient temperatures display a linear T   versus 1/t behavior, with an intercept equal to the undisturbed formation temperature.