A statistical method for correcting log-derived temperatures

Statistical analysis of subsurface temperatures in the Malay Basin has been carried out in order to (1) determine appropriate correction methods and c orrection factors for temperatures obtained from wireline logs and (2) inve stigate the confidence levels associated with those corrections. DST temper atures were taken as 'ground truth' for these corrections. For individual l og-derived temperatures the correction factor fs, which is applied to the d ifference between the measured temperature and the surface temperature, is given by f(s) = (- 0.1462Ln(TSC)+1.699)/(0.572 .Z(0.075)), where TSC is the time since end of mud circulation in hours and Z is the de pth in metres. For temperatures that have already been corrected by extrapo lation using Horner plots, f(HP) is given by f(HP) = - 0.132Ln(TSC) + 1.52, where TSC is the maximum time since circulation stopped (hours) in the Horn er plot set. Uncertainties inf, decrease markedly as TSC and depth increase . Uncertainties in f(HP) decrease as maximum TSC and the number of consistent temperature measurements at a given depth increase. Although these correction factors were developed using data from a single b asin, our experience suggests that they can be used with reasonable confide nce in many or most other geological provinces. Additional local calibratio ns would help test and refine this hypothesis.