DrillString Vibration With Hole-Enlarging Tools: Analysis and Avoidance

Abstract

In high-risk, high-cost environments, such as ultra-deep waters, refining advanced technologies for the successful completion of wells is paramount. Challenges are still very much associated with complex bottomhole assemblies (BHAs) and with the vibration of the drillstring when used with hole enlarging tools. These tools with complex profiles and designs become additional excitation sources of vibration. The more widespread use of downhole tools for both directional telemetry and logging-while-drilling (LWD) applications, as part of the front line data acquisition system within the drilling process, has made reliability a prime area of importance. This paper presents and validates an existing model to predict severe damaging vibrations. It also provides analysis techniques and guidelines to successfully avoid the vibration damage to downhole tools and to their associated downhole assemblies when using hole enlarging tools, such as hole openers and underreamers. The dynamic analysis model is based on forced frequency response (FFR) to solve for resonant frequencies. In addition, a mathematical formulation includes viscous, axial, torsional, and structural damping mechanisms. With careful consideration of input parameters and the judicious analysis of results, we demonstrated that drillstring vibration can be avoided by determining the three-dimensional vibrational response at selected excitations that are likely to cause them. In addition, the analysis provides an estimate of relative bending stresses, shear forces, and lateral displacements for the assembly used. Based on the study, severe vibrations causing potentially damaging operating conditions that had been a major problem in nearby wells were avoided. Steps required to estimate the operating range of the drilling parameter such as weight on bit and rotational speeds to mitigate and avoid the downhole tool failures due to vibration are given. Extensive simulations were performed to compare the data from the downhole vibration sensors; this paper includes severe vibration incidence data from three case studies in which the model estimated, predicted, and avoided severe vibration (Samuel, R., et al., 2006, “Vibration Analysis Model Prediction and Avoidance: A Case History,” Paper SPE 102134 Presented at the IADC India Conference, Mumbai, India, Oct. 16–18; Samuel, R., 2010, “Vibration Analysis for Hole Enlarging Tools” SPE 134512, Annual Technical Conference, Florence, Italy).