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Caijin Y.,Southwest Jiaotong University | Caijin Y.,Tsinghua University | Zaibin C.,Drilling and Production Technology Research Institute | Zaibin C.,China National Offshore Oil Corporation | And 6 more authors.
Journal of Offshore Mechanics and Arctic Engineering | Year: 2015

Excessive torque and drag in the wellbore can result in the buckling and the failure of the drillstring. Accurate predicting torque and drag is important in drilling operations. Due to the nature of the drilling, determination of torque and drag is a dynamic problem. A multibody dynamic model of the drillstring for the torque and drag analysis is developed here. Unlike traditional softstring models and stiffstring models, the developed model relaxes the assumption of continuous contact between the drillstring and the wellbore. Moreover, this model can account for overall rigid motion, three-dimensional (3D) rotation and large deformation of the drillstring with large-scale slenderness ratio and random contact between the drillstring and the wellbore. The effects of local protuberant components of the drillstring, such as the drillpipe subs and the stabilizers are also incorporated in the current model, which are not considered in most of existing models. Numerical analysis with three cases is carried out to show the application of the developed model in predicting torque and drag in the wellbore. © 2015 by ASME.

Wang N.,State Key Laboratory of Offshore Oil Exploration | Wang N.,Tsinghua University | Cheng Z.,Tsinghua University | Cheng Z.,China National Offshore Oil Corporation | And 9 more authors.
Advances in Mechanical Engineering | Year: 2015

This article models the contact between the drillstring with large slenderness ratio and the extending rigid wellbore based on the multibody dynamics method. The drillstring is modeled as absolute nodal coordinate formulation beams with contact detection points. An algorithm is developed to locate the contact points and calculate the contact forces when the drillstring is sliding and rotating in the wellbore. This provides support force and friction for the moving drillstring and effectively confines it inside the wellbore. A rock penetration model is established based on the rock-breaking velocity equation. The governing equation for the full-hole drilling system including the drillstring and the contact model is established and solved. A rock penetration correction method is proposed to stabilize the computation and to model and simulate the slide drilling process. A field drilling process is modeled and simulated. The simulation result fits the experimental result well. © The Author(s) 2015.

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