Abstract
Lateral and torsional vibrations of drill strings used in oil well operations are considered. This work presents finite-element-based bottom hole assembly model which addresses natural frequencies determination, and torsional and lateral oscillations on the near vertical well. In terms of the excitations of the developed finite-element model, forces are applied on the bit with time history generated using an Auto-Regressive Moving-Average digital filter. Due to the random pattern of the forces at the drill bit, a stochastic dynamic approach is adopted in investigating the problem. The method of Newmark-beta direct integration is used. It is hoped that this study will enhance the interest in using stochastic dynamic techniques in drilling system analysis and design, as they can capture quite appropriately the inherent uncertainty of the bit forces and, potentially, of other sources. The implementation of torsional degree of freedom during the development of MATLAB code has been considered new attribute regarding previous works based on the same research line. The results from the code developed attained a good agreement with the commercial SPA2000 Advanced 14.0.0 Structural Analysis Program software.
Highlights
In the type of deep drilling operations that are commonly used for hydrocarbon exploration and recovery, there are a few common designs
The lower end of the string, consisting of the drill bit, collars and other components that are collectively known as the bottom hole assembly (BHA), is the region of many failures (Macdonald and Bjune 2007)
A finite-element model has been used to study the dynamic behavior of the BHA subjected to stochastic excitations
Summary
In the type of deep drilling operations that are commonly used for hydrocarbon exploration and recovery, there are a few common designs. These drilling operations typically make use of drill strings, which are pipes that transmit both drilling fluid and torque necessary to rotate a drill bit. The top end of a drilling string typically has the machinery necessary to pump the drilling fluid, and either a top or kelly drive to provide torque for the drill bit. Typical problems that are encountered include severe stick–slip, lateral vibration, hole enlargement, which induce poor directional control. This problem causes costly drilling equipment failures
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