Drillstring vibration is a leading cause of downhole-tool failure and premature wear of downhole equipment. The main challenges faced during drilling include performing rapid analyses to determine the root cause of the vibration, clear identification of the active mechanism, and implementation of the appropriate corrective action quickly enough to prevent failure. This paper describes a comprehensive methodology created to identify root causes, vibration mechanisms, and methods to reduce or eliminate drillstring vibration.
A bottomhole assembly (BHA) and drillstring have six degrees of freedom and three dominant modes of vibration: axial, lateral, and torsional. This movement is used to describe the different vibration mechanisms such as stick/slip; bit bounce; bit whirl; BHA whirl, both forward and backward; torsional resonance; bit chatter; modal coupling; and lateral shocks. Data are collected from downhole and surface sensors, as well as cuttings analyses, that measure modes and magnitudes of vibration, tension, compression, and bending within the BHA; drilling parameters; fluid properties; and lithology and rock properties. The methodology uses some or all of these factors to identify the root cause and is enhanced by the ability to summarize the distribution of vibration levels across a run, by histogram analysis, and by the ability to filter across time or depth ranges and filter further on the basis of rig-activity codes.
A combination of factors generates or influences drillstring vibration, including the energy inputs of weight on bit and torque; bit type; BHA design and stabilization; lithology type; geological structures; bit/lithology interaction; borehole and BHA size; hole trajectory; backreaming or rotating off-bottom; hole enlargement; the rig’s electrical system; and, on offshore floating vessels, rig heave....
Improvements in Root-Cause Analysis of Drillstring Vibration
16 November 2016