Vibration Measurements: A Time for Standardisation

Abstract

Abstract Since downhole vibration measurements were introduced in the early 1990's, these measurements have become extremely useful for improving drilling efficiency in most parts of the world. Most operators will specify a vibration sensor of some sort to be run with most MWD (Measurement While Drilling) and LWD (Logging While Drilling) applications. Unlike most other downhole measurements, there is no industrial standard for how to sample, process and present the vibration data. This raises a few issues that this paper attempts to address: Vibration measurements from different companies cannot be readily compared - and it is not known if the different tools and systems will detect the same vibration mechanisms and/or severity of vibrations○Vibration Specifications of MWD and drilling tools from different service providers cannot be compared. It is not possible to compare specifications of the various tools as these are given based on the individual service company's internal vibration definitions This paper looks into the physics and statistics of how four major MWD service providers conduct their vibration measurements. Even though all the service companies basically can measure the same physical parameters such as tri-axial accelerations and instant changes in downhole RPM (Revolutions Per Minute), the data are handled differently when it comes to the physical understanding of the data, as well as the statistical modelling of the vibration severities. To further confuse the issue, the data is also presented differently and on different severity scales. The torque/RPM vibration measurement, commonly referred to as "stick-slip", is well documented by previous publications by the different companies (Chen et. al. 2006). The present paper mostly concentrates on how the different MWD companies measure, process, report and interpret their tri-axial data. An analysis is conducted to establish if the various service companies are tuned to look for the same type of vibrations, or whether different vibration patterns tend to be detected with the various procedures in place. Finally, the need for an industry standard is highlighted, and the MWD industry is challenged to move towards standardisation.