Wellbore and Formation Temperatures During Drilling, Cementing of Casing and Shut-in

The knowledge of downhole and surrounding the wellbore formations temperature is an essential factor during drilling operations, shut p-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. It is very important to estimate the effect of pressure and temperature on the density of the formation fluid. This will permit a more accurate prediction of differential pressure at the bottom-hole and will help to reduce the fluid losses resulting from miscalculated pressure differentials. In areas with high geothermal gradients, the thermal expansion of drilling muds can lead to unintentional underbalance, and a kick may occur. The effect of the borehole temperature recovery process (disturbed by drilling operations) affects the technology of the casing cementing operations. The design of cement slurries becomes more critical when a casing liner is used because the performance requirements should be simultaneously satisfied at the top and at the bottom of the liner. For these reasons it is logical to assume that the bottomhole shut-in temperature should be considered as parameter in the cement slurry design. Assessment of the temperature development during hydration is necessary to determine how fast the cement will reach an acceptable compressive strength before the casing can be released. Temperature surveys following the cementing operation are used for locating the top of the cement column behind casing. Field experience shows that in some cases the temperature anomalies caused by the heat of cement hydration can be very substantial. Thus, it is 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 interpretation of geophysical data is used the temperature dependence of mechanical and electrical properties of formations. In the paper we present 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. We also present several techniques of calculation of the static formation temperatures.