SONIC WHILE DRILLING - HAVE YOU THOUGHT ABOUT CUTTINGS

Sonic while drilling has long been considered a major goal by the indu stry because of its potential applications: real-time determination of pore pressure and overburden gradients, improved, lithology change de termination, seismic calibration, and detection of seismic reflectors ahead of the bit. Until now, only two methods were available to perfor m sonic measurements while drilling-the use of continuous coring or a specific measurement while drilling (MWD) tool. Unfortunately, both me thods remain very expensive and suffer from technical limitations. A n ew technology [named pulsed ultrasound on cuttings (PUC)] has been dev eloped to measure both compressional and shear-wave velocities directl y on cuttings with dimensions as low as 1 mm. Laboratory and field imp lementations of the method are presented along with its validation aga inst reference measurements.