Improvements in the Root Cause Analysis of Drillstring Vibration

Abstract

Abstract 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, all vibration mechanisms, and methods to reduce or eliminate drillstring vibration on a range of different operations. A 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 is collected from downhole and surface sensors, as well as cutting 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, histogram analysis, and the ability to filter across time or depth ranges and further filter based on rig-activity codes. There is a combination of factors that generate or influence drillstring vibration, including the energy inputs of weight on bit (WOB) and torque (TRQ), bit type, BHA design and stabilization, lithology type, geological structures, bit-lithology interaction, borehole size and BHA size, hole trajectory, backreaming or rotating off bottom, hole enlargement, the rig's electrical system, and on offshore floating vessels, rig heave. The methodology is able to identify and isolate which factors are the root cause of a specific mechanism by incorporating time-based analyses with depth-based logs and plotting a to-scale BHA to identify correlations of the bit position, stabilizer, and other BHA components to formation types and boundaries, hole-size changes, and casing positions. This enables a significantly faster data analysis and a more rapid assessment of the root cause of the vibration, thereby delivering specific benefits through identifying and then reducing or eliminating drillstring vibration on a range of different operations.