ACTIVITY DESCRIPTION OVERVIEW
 
Activity Description and Location
 
Within Australian Commonwealth waters offshore from Western Australia, TGS proposes to acquire multi-client (MC) two-dimensional (2D) and three-dimensional (3D) marine seismic surveys (MSS) within the North West Shelf Region (NWSR) South MC MSS operational area. The basin-wide NWSR South MC MSS EP comprises an operational area that is more than 300,000 square kilometres with water depths ranging from approximately 25–5,700 metres (m). The operational area extends from Kalbarri northwards to the waters off Port Hedland.
 
TGS proposes to undertake individual 2D and 3D surveys within the NWSR South MC MSS operational area using a purpose-built seismic vessel. During surveys, it is possible that the survey vessel will be refuelled at sea, either within or immediately adjacent to the survey area. At-sea refuelling will only take place during daylight hours and not within a minimum distance of 25 km from any emergent land or shallow water features. A support vessel will accompany the survey vessel.
 
Operational Details
 
In terms of technical methods and procedures, the proposed MSS will be typical 2D and 3D surveys that are similar to previous surveys conducted in Australian marine waters, as no unique or unusual equipment or operations are proposed. During the proposed survey activities, the survey vessels will traverse a series of pre-determined sail lines within the NWSR South MC MSS operational area at a speed of ~4.5 knots. For both 2D and 3D surveys, the operating pressure for the seismic acoustic source will be ~2,000 psi, with the 3D acoustic source deployed in two arrays. The largest sound source for any survey within the operational area will have a capacity no greater than 4,120 cubic inches. The sound pulses generated will have a sound pressure level no higher than 260 dB re 1μPa (at 1 m) at frequencies extending up to ~200 Hz.
 
Timing of the Activity
 
The NWSR South MC MSS EP is designed to cover a period of five years, although the timing of commencement and duration of individual surveys within the NWSR South MC MSS operational area have not yet been determined.