Mitigating Drilling Dysfunction: Stopping HFTO Where it Starts

Abstract

Abstract This paper presents development of a system to test the origins of high-frequency torsional oscillation (HFTO) and identify the physical cause that allow for building information, which will alleviate this damaging dysfunction. It will present field data where the actual amplitude of HFTO is a complex function of many parameters in which both drill-bit speed and weight on the bit are extremely significant. The HFTO amplitude will increase with both parameters to a peak and then a further increase will reduce the actual vibration. To characterize these relations, a facility was built in our Research Centre in Cambridge, UK, to test HFTO in a laboratory environment. A torsional equivalent to a mass spring resonator was used. The facility allows for drilling under identical drilling conditions with HFTO enabled or disabled. It will be shown that the origin of HFTO is at the actual cutting structure contact with the formation. The HFTO is not driven by the broadband bit drilling noise but by the actual bit cutter's interaction with the formation rock. It is these interactions that drive the speed and weight on bit (WOB) characteristics observed in downhole operations. The characteristics and scale of the dysfunction are dependent upon the formation, the cutting structure, as well as the cutter profiles. This new knowledge will enable bits to be built that will alleviate HFTO rather than drive it.