relevant persons information wheatstone 4D-seismic survey
Chevron Australia aims to conduct a 4D-seismic survey over the Wheatstone and Iago gas fields, located offshore Western Australia.
The proposed survey is part of standard reservoir management practice and use conventional seismic survey equipment and methodology. It will serve as a “timelapse” measurement and will be compared to data acquired in 2011/2012 to help Chevron Australia understand how the Wheatstone and Iago reservoirs are performing.
location and water depth
The survey will be conducted within the WA-46-L, WA-47-L, WA-48-L petroleum permits and surrounding permits located approximately 150 kilometres north-west of Dampier at depths from 80 to 1,140 metres. At its closest point the survey will be approximately 37 kilometres from the Montebello Islands.
The survey area is approximately 1,644 square kilometres while the operational area is approximately 3,730 square kilometres. See figures 1 and 2.
schedule and duration
Seismic surveys use sound energy to capture data to develop an accurate and high-quality image of geological features.
A seismic vessel will traverse a series of ‘sail lines’ within the operational area at around 8 kilometres per hour.
The vessel will use compressed air to create ‘bubbles’ that collapse and send directionally focused low-frequency sound waves towards the sea floor. A series of hydrophones, located in a series of streamers trailed behind the vessel, capture the returning sound waves and record the data that is later interpreted by geoscientists.
The seismic vessel will tow up to 14 streamers at lengths of up to 7 kilometres and depths of up to 25 metres; and 2 source arrays of approximately 4,130 cubic inches at a depth of 5-8 metres.
It will be supported by vessels and a helicopter.
Seismic surveying is an established science with strict requirements and operational procedures in place to minimise potential impact to the marine environment, which includes marine mammals.
As part of the environmental approval process associated with an environment plan, we will outline the general marine environment and control measures to manage the potential impacts and risks. Proposed control measures are outlined in Table 1 and additional control measures identified during consultation with relevant persons and the public comment period will be considered for inclusion.
EMBA – environment that may be affected
4D seismic surveys have the potential for environment interactions, known as ‘aspects’.
All planned aspects can result in environmental impacts and changes to the environment, and may present environmental risks within the operational area, with the exception of underwater sound emission, which can extend approximately 51 kilometres from the hydrophones.
Unplanned releases and events may occur while conducting activities.
The size of the ‘environment that may be affected’, also known as an ‘EMBA’ is based on an emergency condition’s worst case environmental scenario, which in this case is an unplanned spill event from a vessel collision.
The EMBA has been defined through combining 300 simulations of vessel collisions under three different hydrological and meteorological conditions.
Control measures to prevent this event are in place, but Chevron Australia is required to assess this highly unlikely scenario.
In this scenario, cultural, ecological and social values and sensitivities may be exposed to hydrocarbons. These are considered environmental risks because they are not planned to occur.
Petroleum activities in Commonwealth waters are regulated by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA). Before petroleum activities can take place, Chevron Australia must develop an Environment Plan which will be assessed by NOPSEMA in accordance with the requirements of the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations (2009). These regulations require Chevron Australia to consult with relevant persons whose functions, interests and activities may be affected by the petroleum activity.
The Environment Plan will describe the environment in which the petroleum activity takes place, an assessment of the potential environmental impacts and risks arising from the activity, and the identification of control measures to manage environmental impacts and risks to acceptable levels that are as low as reasonably practicable.
The environment plan outlines how Chevron Australia has engaged with ‘relevant persons’, whose interests, functions, and activities may be affected and how their feedback has been considered and addressed.
Seismic survey plans must be submitted to NOPSEMA and published on its website for a 30-day public comment period.
Chevron Australia welcomes feedback from relevant persons prior to the public comment period to ensure feedback is incorporated into the draft environment plan before it is submitted to NOPSEMA and advertised on NOPSEMA’s website.
communications with marine users
Seismic vessels will operate within the operational area and marine notices will be issued before work starts to notify other mariners that access to the operational area may be limited. This will include a temporary 500-metre exclusion zone around the primary vessel and streamers during seismic operations.
Updates will be provided on vessel movements and activities to meet relevant persons’ needs. On-the-water communications and cooperation is a Chevron Australia priority.
We will ensure open radio access between other ocean users and the primary seismic vessel to enhance on-the-water communications. Radio information will be communicated to relevant potentially affected parties as part of the start-up notification process before starting the survey.
other relevant persons
Chevron Australia also recognises the interests, functions, and activities of other relevant persons that may be affected by the surveying.
Chevron Australia is committed to engaging early and working proactively with relevant persons and will keep informed and provide responses to any relevant person that identifies an interest in the planned seismic survey.
impacts, risks and proposed controls
Summary of impacts/risks and key proposed controls – view Table 1.
We are committed to engaging with Traditional Owners and Custodians, commercial fishers, recreational groups and other relevant individuals and organisations, as required by regulation.
We are seeking your feedback if you consider your functions, interests or activities may be affected based on the information outlined in table 1.
Let us know if you consider there are any control measures we could implement to eliminate, reduce or avoid an effect.
You can contact us tollfree at 1800 225 195 or leave feedback online below.
If a relevant person asks that their feedback be treated as confidential, Chevron Australia will make this known to NOPSEMA and the information will be kept confidential.
Your feedback during the consultation period will be considered and incorporated into the environment plan.
We commit to keeping you informed and providing responses to any relevant person who so requests.
If you choose to provide feedback on this proposal, Chevron Australia will collect your name and contact details, in addition to your comments, for the purposes of maintaining contact with you and inclusion of your feedback in our submission to NOPSEMA. Provision of this information is purely voluntary, however if you choose not to provide it, we may not be able to contact you in the future regarding your submission. Chevron may transfer your information to NOPSEMA, if required and if you do not identify it as sensitive, and to other Chevron affiliates including our head office based in the United States. For further information regarding how we protect your personal information, and your rights, please refer to our privacy notice.
Figure 2. Areas identified in the seismic survey. Refer to Table 2 for coordinates and depths of locations indicated in map above
Table 1: Summary of impacts/risks and key proposed controls – view here.
Table 2: Coordinates and depths of the seismic survey areas – view here.