A Prediction Model of Casing Wear in Extended-Reach Drilling With Buckled Drillstring

Abstract

Buckled drillstring easily existed in extended-reach drilling (ERD) engineering, causing casing wear more severe. However, the effect of the buckled drillstring on casing wear prediction is going unheeded in long-term studies. To solve the issue, this paper proposes a new model, named as circumferential casing wear depth (CCWD) model, based on the energy principle and the more complicated geometry relationship than that in casing wear groove depth (CWGD) model. Meanwhile, sensitivity analysis of parameters clearly describes the changing trends among them. With the established composite wear models, the change of casing wear depth versus drilling footage under different composite wear cases is also discussed. The results show that the severe casing wear may occur if there is the buckled drillstring; due to the greater contact force and more sophisticated wear shape than those under nonbuckling condition, a shorter drilling footage could make a larger calculation error when only CWGD model is used. In the case study, the method of the inversion of casing wear factor from the drilled well can be used to predict the well whose structure resembles it; the revised coefficient, the maximum risky casing wear depth can be evaluated for each wellbore section to avoid drilling engineering failure. The new model provides a practical method to improve the prediction accuracy of casing wear in ERD. Neglecting the effect of the buckled drillstring will make the prediction underestimated and a great economic loss, which is significant for ERD.