8. Temperature Investigations in the Petroleum Industry

The knowledge of downhole and surrounding the wellbore formations temperature is an essential factor during drilling operations, shut-in and cementing of casing periods. The downhole temperatures while drilling affects the viscosity of the drilling mud and, subsequently, the frictional pressure losses; the performance of drilling bits in hot wells; the density of drilling fluids a.o. In deep and hot wells, the densities of water/oil muds and brines can be significantly different from those measured at surface conditions. For this reason determining the density of drilling mud under downhole conditions is needed for calculating the actual hydrostatic pressure in a well. The borehole temperature recovery process (disturbed by drilling operations) affects the technology of the casing cementing operations. Temperature surveys following the cementing operation are used for locating the top of the cement column behind casing and are very important to predict the temperature increase during the cement setting. This will enable to determine the optimal time lapse between cementing and temperature survey. During the shut-in period in the wellbore are conducted transient downhole and bottomhole temperature surveys and geophysical logging. In this are presented methods of determination of the drilling mud circulation temperatures, borehole temperatures during cementing of casing and temperature in surrounding wellbore formations during drilling and shut-in periods. Also several techniques of calculation of the static formation temperatures are considered.