Field Investigation of the Effects of Stick-Slip, Lateral, and Whirl Vibrations on Roller Cone Bit Performance

Abstract

Abstract The effects of downhole vibrations on polycrystalline diamond compact (PDC) bit performance have been well discussed in recent years. However, most research on the downhole dynamics of roller cone bits has focused on axial vibration and its effects on bit performance. The questions which remain to be answered are: What kind of vibrations does a roller cone bit experience, and what are the effects of these vibrations on roller cone bit performance? To investigate these questions, a series of field tests was conducted in a full scale drilling research rig, with downhole vibration data recorded by an advanced instrumented sub. Soft to medium hard formations were drilled using four 8½-in. roller cone bits (IADC Code 517. Three kinds of harmful vibrations were observed, and their effects on bit performance in terms of rate of penetration (ROP), insert breakage, and bearing/seal and bit life are discussed.