Investigation of the Combined Effects of Temperature and Large-Scale Tortuosity on Friction-Factor Profile in Straight Inclined Sections

Abstract

Summary This paper studies the implicit effects of temperature and wellbore tortuosity on the mechanical friction factor in torque-and-drag models applied to straight inclined sections. Experimental work was performed to measure the variation of viscosity and density of a water-based-mud (WBM) sample with respect to temperature and pressure. The effect of wellbore tortuosity was accounted for by means of the dogleg-severity (DLS) filter, which is presented in the paper. Experimentally obtained parameters were included in an algorithm for friction-factor-profile back calculation using a selected torque-and-drag model. A field case is presented to show this approach. The calculated friction factors were compared with those obtained by using the original torque-and-drag model and the averaged friction-factor values provided by the field operator, and the deviation mechanisms were discussed. Comparing the obtained results, we concluded that pressure and temperature, accounted for through variation in fluid buoyancy with depth, affect friction factor just marginally for rotation off-bottom and negligibly for tripping operations. The unplanned large-scale tortuosity affects the ultimate friction factor more significantly. The magnitude of the studied effects would greatly depend on the wellbore conditions. By including additional parameters in the traditional torque-and-drag models, researchers and engineers would be able to evaluate the effects of these parameters on the friction-factor estimation. It can help to estimate the range of friction forces during the planning phase and explain abnormal trends in post-run analysis.