Casing Wear Prediction Model Based on Drill String Whirling Motion in Extended-Reach Drilling

Abstract

Casing wear has become an increasingly urgent research topic alongside advancements in extended-reach drilling (ERD) engineering. The drill string in an ERD operation is likely to undergo whirling motion, which is known to impact casing wear prediction accuracy; there have not yet been long-term studies on the related mechanisms, however. In this study, we develop a new prediction model called circumferential casing wear model (CCWD) based on the energy principle and the geometric properties, which accounts for the effects of drill string whirling motion on casing wear. Besides, composite casing wear models considering with the CCWD and casing wear groove model (CWGD) are also discussed. The results via case study to find that the proposed CCWD model of whirling motion can contribute to the accuracy of casing wear prediction. If the whirling motion is ignored, a large prediction error could occurred when only CWGD model is used. In the sensitivity analysis, the worn casing depth may increase alongside increases in whirling motion angular velocity, rotary table angular velocity, sliding and rolling friction coefficient, outer tool joint radius, and drill string weight. Slight variations in whirling motion angular velocity and rolling friction coefficient can cause substantial casing wear. Thus whirling motion must be strictly controlled during the drilling process to prevent engineering failure. To this effect, the model presented in this paper has both theoretical and practical applications for enhancing the accuracy of casing wear prediction to develop oil and gas reservoirs in ERD.