Bottom‐hole temperature stabilization with continued circulation of drilling mud

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Abstract
Determination of true formation temperature from measured bottom‐hole temperature (BHT) is important for well log interpretation and geothermal studies, especially with the current realization of the role of temperature in hydrocarbon maturation. A “bulk” thermal diffusivity of the borehole‐rock system of approximately [Formula: see text], initially suggested by Leblanc et al (1982), is confirmed by comparison with a two‐media borehole model. In general, time‐consecutive BHT measurements exhibit slower stabilization than those predicted by thermal conduction models. A simple model of thermal stabilization of a borehole with continued circulation after cessation of drilling is proposed. By modeling the thermal sink due to continued circulation of drilling mud as an exponentially decaying sink, thermal stabilization curves more consistent with observation are obtained. A good estimate of true formation temperature can be obtained by a curve‐matching technique where the observed BHT data are well behaved and the physical conditions in the borehole closely match the assumed model. However, it is virtually impossible in some cases to obtain a precise estimate of true formation temperature with BHT measurements from well log runs with current BHT stabilization models.

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