Impact of survey design and acquisition technology on 3D Marine Mega-survey success, a recent example from Southern Australia

Abstract

The objective of the seismic survey discussed here was to rapidly explore deep targets over 12000 km2 of frontier permits. Heavy seas with a strong south-westerly swell and strong ocean currents, coupled with stormy weather conditions create risk for both seismic quality and turnaround, limiting the survey to a tight weather window. These harsh metocean conditions were compunded by the remote setting; both factors strongly influenced the survey design and posed the biggest challenge to delivering a consistent high quality seismic dataset. The solution required a huge receiver spread covering over 11.5 square kilometers and modern equipment to withstand an extended period in these conditions. Two main technology solutions were also implemented to deliver the project. The first was Fan shooting where cables are laid out with greater spacing at the end or the spread compared to near the vessel. The second is termed intelligent infill modeling where variable coverage is modeled to determine acceptable offset gaps, and then the data quality impact is predicted from actual coverage during acquisition, to aid real time infill decisions. This was calibrated against real data decimation tests before the survey and found to be accurate. The wide and long receiver spread deployed in this project led to several vendor production records. These included production records for one day at 143.6km2, one week at 919 km2, and one month at 3,056km2, while still delivering very high quality seismic data. The design helped the acquisition to continue in severe swell conditions without introducing detrimental noise in the data, helped by real time, flexible, on-board seismic processing to confirm when swell noise could or could not be removed from the data. Infill management and fanning of the streamers contributed to an overall reduction of the infill.