Abstract: Accurate prediction and control of friction torque during the design and construction of drilling phases can prevent drilling accidents, and the shaft friction coefficient is a key factor in predicting friction torque. Therefore, we predicted the friction coefficients for the casing and open-hole sections for highly-deviated well drilling based on a calculation model for friction torque. This was based on drill-string dynamics and data from a near-bit, multi-parameter measuring instrument. The results were successfully applied to the analysis and control of friction torque in the third-spud drilling stage of adjacent wells of the same type. The field application results revealed that the friction coefficient of the actual drill casing was 0.27~0.29, and the friction coefficient of the open hole was 0.39~0.41, both of which are higher than the empirical values. The error between the predicted and actual values of the hook load and the torque of the case satisfied the construction accuracy requirements. The friction torque during actual drilling was monitored in real time to detect abnormal changes based on the friction torque prediction chart, which ensured smooth construction of the well. The results provide a scientific basis for optimizing drilling equipment and the well profile of highly deviated wells, and for planning the on-site drilling construction.

Key words: drill-string dynamics, friction torque prediction, friction coefficient, computation model, field application