CGG Services Australia (CGG) is proposing to undertake the Regia three-dimensional (3D) marine seismic survey (MSS) in Commonwealth waters of the Otway Basin. The purpose of the Regia 3D MSS is to collect high-quality geophysical data about rock formations and structures beneath the seabed and assess potential for new oil and gas discoveries.
The Regia 3D MSS is a typical 3D survey using methods and procedures like others conducted in Australian waters. No unique or unusual equipment or operations are proposed. The active source area comprises the area within which 3D seismic acquisition will be undertaken and has a maximum sail line distance of 1,700 km. The active source area is surrounded by a larger operational area (approximately 4,000 km2), for the purpose of line turns, run-ins, run-outs, seismic testing, and support activities. The operational area at its closest is approximately 12 km south of Port Fairy. The seismic survey will be undertaken in water depths no shallower than 50 m, and no deeper than 200 m.
The survey will involve a single seismic survey vessel towing a seismic source array with a total volume of 2,820 cubic inches (in3), at a water depth of between 5 - 10 m. The seismic source will use compressed air to emit regular pulses of sound that reflect off the seabed and underlying rock formations. The reflected sound wave will be received by up to 14 hydrophone streamers. Each streamer will be up to 8,100 m in length, spaced approximately 100 m apart and towed at a depth of approximately 25 m. During the survey, the seismic survey vessel will travel at a speed of approximately 4.5 knots, discharging the seismic source approximately every 12.5 m. The survey vessel will typically acquire seismic data along a series of adjacent and parallel lines in a “racetrack” pattern. When the vessel completes the line, it will turn again to follow another line offset approximately 500 m from the first. This pattern is repeated until the required coverage is completed.
The Regia 3D MSS will take a maximum of 90 days to acquire, and may be undertaken in any month except January, February, and March. The precise timing of the survey is subject to vessel availability, weather conditions and other operational considerations, and will consider the seasonality of environmental sensitivities, where practicable.