Analysis of multi-mode nonlinear coupled axial-transverse drillstring vibration in vibration assisted rotary drilling

作者：Ghasemloonia Ahmad^*; Rideout D Geoff; Butt Stephen D

来源：Journal of Petroleum Science and Engineering, 2014, 116: 36-49.

DOI：10.1016/j.petro1.2014.02.014

• drillstring model
• vibration-assisted drilling
• coupled nonlinear axial-transverse vibration
• multi-span BHA
• Bypassing PDE's
• wellbore contact
• multi-mode analysis

Unwanted vibration modes of a drillstring can result in inefficient drilling, and damage to the drillstring, bit, BHA components, MWD tools and mud motors. Bottom-hole assembly (BHA) configuration design, shock sub parameter tuning, and establishing drilling parameters such as rotary speed and weigh-on-bit can be improved using computer simulation of a drillstring and its vibration modes. Drilling tools are under development to apply axial vibrations for the purpose of overcoming drillstring-wellbore friction, facilitating cutting removal and improving the rate of penetration (ROP) of the bit. Predicting the effects (both desired and undesired) of such axial vibration generator tools is becoming increasingly important to industry. In this paper, the coupled nonlinear axial-transverse dynamics of the entire drillstring are modeled and lateral instabilities are qualitatively studied. The drillstring includes the pipes, a multi-span BHA with shock sub, and a force generator tool near the bit. The multi-span BHA model enables more accurate natural frequency prediction and multi-mode contact analysis of the drillstring and wellbore. The governing equations are obtained using the "Bypassing PDE's" method with the expanded Galerkin's method, which enables finding the symbolic solution of the governing equations. The effects of mud damping, driving torque, and spatially varying axial load are also included, along with nonlinearities due to geometry, axial stiffening, strain energy and Hertzian contact forces. Simulations reveal resonant frequencies and show the relative severity of the contact in each span of the BHA. The model features fast running time compared to a high-order finite element model against which it is validated.

• 出版日期2014-4