3D Oil Limited (3D Oil) is proposing to undertake the Sauropod three-dimensional (3D) marine seismic survey (MSS) in Commonwealth waters of the Roebuck Basin, within exploration permit WA-527-P. The purpose of the Sauropod 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 Sauropod 3D MSS is a typical 3D survey using methods and procedures similar to others conducted in Australian waters. No unique or unusual equipment or operations are proposed.
The Acquisition Area comprises the area within which 3D seismic acquisition will be undertaken and covers approximately 3,500 km2. The Acquisition Area is surrounded by a larger Operational Area (approximately 6,000 km2), for the purpose of line turns, run-ins, run-outs, seismic testing and support activities. The Operational Area at its closest is approximately 120 km north of Eighty Mile Beach and 230 km west of Broome. The seismic survey will be undertaken in water depths between approximately 95 m to 172 m.
The survey will involve a single seismic survey vessel towing a seismic source array with a total volume of 3,090 cubic inches (in3), at a water depth of approximately 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 12 hydrophone streamers. Each streamer will be up to 7,000 m in length, spaced 75 m apart and towed at a depth of approximately 15 m. During the survey, the seismic survey vessel will travel at a speed of approximately 4.5 knots, discharging the seismic source approximately every 5 seconds. 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 450 m from the first. This pattern is repeated until the required coverage is completed.
The Sauropod 3D MSS will take a maximum of 60 days to acquire, and will be undertaken within the acquisition window of January to April inclusive of 2021. The precise timing of the survey is subject to vessel availability, weather conditions and other operational considerations, and will take into account the seasonality of environmental sensitivities, where practicable.