Wellbore friction has led to an increase in the temperature of the drilling fluid downhole as well as heating of the drillpipe and the bottomhole assembly. Severe downhole heating can lead to potential well-control safety issues and result in costly remedial efforts. An estimation of the increase in temperature of the drilling fluid downhole as a result of this wellbore friction will certainly help in taking measures to prevent such dire circumstances and will lead to an improved drilling plan.
This study uses a simple analytical model to analyze the heat generated from borehole friction and then predict the downhole temperatures at any depth in the well during a drilling operation. The torque acting on the drillstring as a result of contact forces has been used to model the heat generated from friction, and a steady-state heat transfer solution has been presented. The model also incorporates the heat generated downhole owing to frictional pressure losses along the drillstring as well as across the bit.
Practical field cases, including a horizontal well, have been presented in the paper to validate the model. Downhole temperatures of the drilling fluid have been calculated along the well profile using the model and then compared with the field data measured using MWD tools. The zones having the maximum increase in temperatures can be identified based on the temperature profile generated during the drilling operation. The impact of drilling parameters on temperatures has also been analyzed and can be used effectively to maintain a better check on undesired temperatures.
This simple analytical model can be suitably applied to field cases based on the well profile and can be effectively used to predict the maximum temperatures to be encountered downhole while drilling ahead as planned. An accurate estimation of maximum temperatures will help us prevent severe downhole friction heating in the future.