The Gorgon OBN Seismic Survey (Survey) will be undertaken over the Gorgon gas field, located in the Commonwealth waters of the North West Shelf, Western Australia (WA). The Survey operational area is situated approximately 65 km west of Barrow Island and approximately 140 km north of Onslow on the WA mainland (Figure 1-1) in water depths ranging from approximately 80 to 1,100 m.
 
The Survey area includes the Chevron Australia Pty Ltd operated titles WA-37-L, WA-38-L and WA-14-R. Additionally Petroleum Access Authority WA-81-AA has been obtained through the National Offshore Petroleum Titles Administrator (NOPTA) to allow access to surrounding titles.
 
The activities described in the Plan are planned to commence from approximately mid-October with an expected acquisition start date of 01 November 2015. The Survey is expected to take up to approximately 210 days to complete, depending on weather conditions and is planned to be completed by the end of June 2016.
 
The Gorgon OBN Seismic Survey is a time-lapse baseline seismic survey that aims to provide an understanding of reservoir behaviour of the Gorgon gas field both pre and post hydrocarbon production. The activities associated with the Survey include:
Deployment of OBN units and Pressure Inverted Echo Sounders (PIES)
Seismic acquisition
Supporting activities
 
An offshore installation vessel, hereafter referred to as the OBN vessel, will be used to deploy a network of nodes to the seabed with the use of a remotely operated vehicle (ROV). The nodes are discrete units, not connected by any cables and are typically 1 m2 in size. Sufficient nodes are not available to cover the whole Survey area at once; therefore, nodes will be repositioned in the node area as the data has been acquired. During this process nodes will be retrieved back to the OBN vessel for data downloading and battery charging before being redeployed back to the seabed. Nodes are expected to remain at each location on the seabed for approximately 20 to 50 days as operationally required and will continuously record.