Downhole vibrations is still a problem to solve because models have failed to be predictive and surface measurements do not reproduce downhole phenomena precisely. The paper describes the instrumentation of PDC bits with accelerometers, strain gauges and contact sensors. From these sensors it has been possible to produce direct measurements in lime domain and frequency domain of: instantaneous RPM, accelerations along the three axis, downhole WOB, downhole torque, power dissipated at the bit, eccentricity of hole, bit center trajectory, also indirect measurements of downhole estimated ROP, wear, specific energy. Military type micro electronics of the latest technology have been used to integrate evervthing in the bit shank. With these measurements dynamics can be analyzed : stick slip and whirl are clearly identified. Lab tests have been performed with promising results. Three campaigns have been done in the field to confirm the lab results with different bit profiles in France and UK. Some of the recorded results compare well to the results of existing BHA models. The paper discusses these results and outlines the future developments. P. 457

This paper was prepared for presentation at the 1998 SPE Annual Technical Conference and Exhibition held in New Orleans, Louisiana, 27-30 September 1998.