Reducing Target Uncertainties and Guiding Drilling Using Seismic While Drilling Technology, a Novel Approach in Andaman Sea Deepwater

Abstract

Abstract Seismic while drilling (SWD) technology was first time being used by Oil and Natural Gas Corporation, ONGC recently, on their Andaman Seas deepwater drilling campaign. Numerous publications have been made by the industry experts over the past 10 year on SWD technology In this case study we demonstrate the practical applications of SWD technology that help to guide the real-time drilling process with effective cost and time in acquiring checkshot data. ONGC has started exploration campaign in Andaman deep water area recently in 2011. The drilling was commenced with very limited information available from surface seismic, because of no well control in the area. By virtue of surface seismic technique, uncertainties are always associated with it. Uncertainties in seismic impacts the well plan and safety, which effectively impacts the well cost. Any technology which can reduce the seismic uncertainties and risks can be useful to reduce the cost and enhance safety. In this paper a case example is presented, where real time checkshot was acquired without disturbing the normal drilling operation. The real-time checkshot was recorded at every drill string stand and recorded waveform was transmitted uphole through mud telemetry system. The computed time-depth function was used to refine pre-drill velocity model and this was subsequently used to update the drilling target prognosis depths and geomechanics model. Real-time checkshot also confirmed the drill bit position on the surface seismic section. Updated seismic lookahead give confidence to ONGC to continue drill ahead with single 12.25" hole to reach their final TD at 3700m. All targets were reached within a few meters errors of the prediction. This case study demonstrated that SWD technique added considerable values in helping eliminating drilling 17.5" enlarge hole and 13 3/8" casing run.