A computer system (Tln-SFT) has been developed for the application of the method based on logarithmic transformation regressions for the determination of static formation temperatures (SFTs) in geothermal boreholes. The system was designed to reproduce the full thermal recovery processes occurred during the cessation of the borehole drilling stage. The system is also capable to applicate multiple linear and polynomial (from quadratic to eight-order) regression models to BHT and log-transformation (Tln) shut-in times. Tln-SFT has been programmed using advances of the information technology to perform more efficiently computations of the selection of the best regression models by using four statistical criteria: (i) the coefficient of determination as a fitting quality parameter; (ii) the sum of the normalized squared residuals; (iii) the absolute extrapolation, as a dimensionless statistical parameter that enables the accuracy of each regression model to be evaluated through the extrapolation of the last temperature measured of the data set; and (iv) the deviation percentage between the measured and predicted BHT data. Tln-SFT may be friendly and rapidly executed by using any personal computer for the determination of the SFT. The Tln-SFT was validated using synthetic data sets where the true formation temperature (TFT) was known with accuracy. Finally, the practical use and prediction efficiency of the Tln-SFT was highlighted and demonstrated because it only requires the use of the original thermal recovery data (BHT and shut-in time) as the main input data, which represents an enormous advantage over most of the analytical and numerical methods reported in the literature that require a large number of measurements (e.g. circulation time, the thermophysical and transport properties of the formation or drilling fluid, among others).

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