Mitigating Downhole Vibrations in Bottom Hole Assemblies Using Finite Element Analysis

Abstract

Abstract Mitigating downhole vibrations is paramount to safe and cost-effective drilling. Excessive vibrations in bottom hole assemblies (BHA) generated from rock-bit interactions can be quantified and hence minimized using finite element dynamic analysis as a tool. Hence, improving rate of penetrations (ROP), minimize BHA failures, high cost savings and ultimately eliminate drilling accidents. Extensive research has been done in order to better understand the three main modes that drive these vibrations to undesired magnitudes. These modes are: axial, lateral and torsional vibrations. Axial vibrations are better known as ‘bit-bouncing’, lateral as ‘bit whirling’ and torsional vibration are known as ‘stick-slip’ which is the most common of these three. Previous research has focused on these modes individually and coupling of two of these, but no study using Finite Element Analysis (FEA) has been done considering these three in the same model. The modern finite element analysis tool utilized in this study provides an opportunity to couple axial, lateral and torsional vibrations for planning and optimization of bottom hole assemblies. This is possible due to the newest developments in computing power and better discretization algorithms. A superimposition of all three vibration modes allows the user to physically see where and when the composite resonance will be generated. In this paper, three vibration modes will be coupled using (FEA) in an attempt to mitigate vibrations affecting the drillstring and BHA by optimizing the amount and positioning of stabilizers. This analysis is focused on the lower portion of the entire drillstring where the vibrations are generated. This holistic approach is beneficial in design safer well plans and bottom hole assemblies