wheatstone well intervention and infill drilling

Chevron Australia, on behalf of the Wheatstone Project joint venture participants, operates the Wheatstone Project (Wheatstone) in Western Australia.  

Wheatstone comprises an offshore processing platform and facilities that gather and partially process gas and associated condensate from the Wheatstone, Iago, Julimar and Brunello gas fields, and deliver it onshore via trunkline for further processing. Onshore facilities include two LNG trains and a domestic gas plant. 

We are currently undertaking a 5-yearly revision of the Wheatstone Well Intervention and Infill Drilling Environment Plan. 

Chevron Australia proposes to conduct infill drilling of seven new wells and well intervention activities on the nine existing production wells, as required, in the Wheatstone and Iago fields, to maintain gas supply to the Wheatstone LNG facility and domestic gas plant. 

Following consultation and consideration of relevant persons' feedback, Chevron Australia has submitted the Wheatstone Well Intervention and Infill Drilling Environment Plan to NOPSEMA for assessment and acceptance. To view, please visit https://info.nopsema.gov.au/

Drilling is scheduled between 2024 and 2028, subject to approvals and drill rig availability. Each well is expected to take about 65 days.

A mobile offshore drilling unit will drill below the seabed. It will be supported by up to three vessels.

Seven infill wells will be drilled.

Based on an assessment, additional work may occur on the nine existing wells, for repairs, maintenance and data acquisition.

Drilling activities will 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 could extend approximately 13 kilometres from the source.

Unplanned releases and events might occur while conducting activities.

Table 3 lists the potential environmental impacts and risks. 

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 loss of well control.

The EMBA has been defined through combining 300 simulations of loss of well control under three different hydrological and meteorological conditions. Figure 2 shows the EMBA.

Control measures to prevent this event are in place, listed in Table 1, 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.

A 500-metre safety exclusion zone will be requested around the drilling unit for the duration of the exploration drilling activities.

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 plans outline 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.

Summary of impacts/risks and key proposed controls – view Table 3.

The initial consultation period has now concluded, however if you consider you may be a relevant person, 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. 

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.