Quantitative Risk Assessment of Cuttings Plug-Induced Pipe Sticking in Long Horizontal Section Wells

Long horizontal section wells significantly enhance single-well production capacity and have become a crucial well type for developing unconventional oil and gas resources. However, due to the extensive accumulation of cuttings beds in long horizontal sections, large-sized drilling tools such as drill bits, stabilizers, and drill collars can mobilize cuttings along the low side of the wellbore during tripping operations. This movement can lead to the formation of cuttings plugs, increasing the risk of pipe sticking and significantly extending non-productive time. Currently, the mechanical mechanism underlying cuttings plug-induced pipe sticking remains unclear. Moreover, risk assessments in drilling operations primarily rely on qualitative experience, resulting in low prediction accuracy and delayed decision-making. To address this issue, this study introduces granular mechanics into the field of oil and gas well tubular mechanics and proposes a quantitative risk assessment method for evaluating cuttings plug-induced pipe sticking. First, considering the “bulldozer effect” of large-sized drilling tools, a predictive model for cuttings plug formation during tripping operations is developed. Second, based on the generalized Pascal’s law, a calculation model is established to quantify the additional axial force and torque exerted by the cuttings plug on the drill string. Finally, incorporating the additional resistance caused by the cuttings plug, the classical drag and torque model is modified. By predicting hook load and top drive/rotary table torque, this method enables the forecasting of downhole cuttings plug-induced pipe sticking. A case study is conducted on a shale gas horizontal well in the Sichuan Basin, China. The results indicate that the predicted location of pipe sticking, as well as the corresponding hook load and top drive torque, closely align with drilling log records. This confirms the feasibility of the proposed quantitative risk assessment method, which can provide valuable guidance for predicting and mitigating the risk of pipe sticking in drilling operations.