Drill Bit Seismic has been used successfully on land and in shallow marine environments for many years and has contributed toward reducing drilling costs and preventing drilling hazard. The technique utilises the acoustic energy radiated during the drilling process and measures signals using sensors deployed on a noisy ground surface, as a reverse of conventional VSP. Massive data processing to extract useful signals from noise provides vital information about the drilling operation.It provides time-depth and formation velocity information at the well site, allowing the position of the bit to be plotted on the surface seismic section as the drilling progresses. By generating look ahead VSP images, the technique can show the drillbit approaching critical horizons, such as overpressure zones. Such information leads to significant cost savings and enhanced safety.The technique has recently been extended to water depths of 500m. This has been used to assist drilling of soft formations in 480m water depth offshore Indonesia and has enabled a casing string to be set at a pre-planned seismic reflector.A lightweight moored array cable was developed in cooperation with OCC (Ocean Cable and Communications) to extend the technology for 3, 000m deep water drilling. The cable has special fairing to attenuate unwanted vortex induced by current. This vortex causes unwanted noise for seismic signal measurements. The cable was used in the water depth of 1, 280m in the Gulf of Mexico, where time-depth data was obtained down to a depth of 3, 810m below MSL, drilling in soft formations with a rollercone bit.Such information can be used to calibrate pre-drill velocity models and helps to prevent unexpected occurrences during drilling.