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
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.
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