Experimental study on the sliding friction of cuttings bed and pipe during horizontal-well drilling considering pipe rotation.

Horizontal wells are being used with the increase of oil and gas demand. But cuttings accumulate at the bottom of the annulus to form cuttings bed in horizontal wells. So the movement of the drillpipe can cause serious friction between the drillpipe and cuttings bed, which can lead to stuck drilling, pipe sticking, and serious downhole accidents. Therefore, it is important to study the parameters that affect the friction between the drillpipe and cuttings bed. In this study, by conducting experiments to analyze the comprehensive sliding-friction coefficient (CSFC) between the drillpipe and cuttings bed. By analyzing the effects of pipe depth, cuttings size, fluid viscosity, and drillpipe rotation speed on CSFC, the CSFC value was obtained and a general CSFC model was established. The study provides a foundation for predicting the CSFC and contribute to the calculation of the extended-reach limit of horizontal wells. [Display omitted] • A new experiment for measuring the friction coefficient is conducted. • Genetic programming is used to derive the optimal model. • The comprehensive sliding-friction coefficient with different variables are obtained. • A foundation for predicting the comprehensive sliding-friction coefficient is provided. [ABSTRACT FROM AUTHOR]