Modeling contact of pipes within elliptic and spiralled wellbores using finite element analysis

• A static 3D nonlinear finite element engine capturing mechanics of drillpipes inside wellbores with friction and contact presented.
• Formulations to model contact of circular pipes within elliptical and spiralled wellbores presented.
• Proposed formulation enables to capture the difference between micro and macro tortuosity of wellbores in terms of mechanical damage done on the drillpipe.

This paper addresses the formulation and implementation of a contact algorithm for circular pipes within elliptic and spiralled wellbores using nonlinear finite element analysis. The need for such a capability originates from drilling applications in oil industry. Normally, the drilling bits have circular cross sections and the intention is to drill perfectly circular holes. However, it is quite common that the drilled wellbores show irregularities. This study derives the formulations to calculate the clearances between the pipes and such boreholes, which are essential to detect contact and calculate the associated contact forces. The formulations are described in detail and the implementations and flowcharts are provided as well. A case study is presented to reveal the implications to have such capabilities within a finite element engine, such as capturing the damage on the drillpipes in terms of bending moments.