For this study, four service companies provided specifications for their downhole vibration monitors. It was found that although each can measure basically the same physical parameters, like tri-axial accelerations and instant changes in downhole RPM, physical understandings of the data are handled differently. Statistical modeling of vibration severities are significantly different, as are data presentations and severity scales.
For example, one company uses only peak values above a pre-defined threshold, and the number of peaks over a time interval defines the severity. Another uses both peak and average values, though the averaging procedure was not specified. Moreover, severity definitions used were “complex,” Mr Osnes said.
What all this means is that vibration measurements from different MWD companies can’t be readily compared. Moreover, it’s not known if the different tools and systems will detect the same vibration mechanisms and/or severity of vibrations.
He pointed out that the lack of standardization means that it’s difficult for operators to:
• Compare tool specifications.
• Correlate between wells.
• Transfer experience.
• Build competence.
• Treat damage claims fairly.
• QC data.
• Verify sensor calibration.
A given physical situation can lead to widely different actions and reactions during drilling, depending on which service company is supplying the vibration measurement and advice, he said.
Mr Osnes concluded by urging the industry to establish agreed standards and best practices for how to measure, classify and report measurements of shocks and vibrations during drilling operations. He suggested this standard should include averaging of kinetic energies and high shock events.
SPE/IADC 119877, “MWD Vibration Measurements: A Time for Standardization,” by Svein Magne Osnes, StatoilHydro; Per Amund Amundsen, University of Stavanger; Tore Weltzin, Erik Nyrnes, Brita Lucie Hundstad and Gaute Grindhaug, StatoilHydro, was presented at the 2009 SPE/IADC Drilling Conference & Exhibition, 17-19 March, Amsterdam.
