wheatstone-2 wellhead in situ decommissioning

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. 

In 2011 petroleum titles WA-46-L, WA-47-L, and WA-48-L were granted to the Wheatstone Joint Venturers, and Chevron Australia became the nominated titleholder. The title contains a single wellhead, Wheatstone-2. It was plugged and abandoned in 2008 and Chevron intends to leave the well infrastructure in place.

Following consultation and consideration of relevant persons' feedback, Chevron Australia has submitted the Wheatstone Project Wheatstone-2 Wellhead Decommissioning Environment Plan to NOPSEMA for assessment and acceptance. To view, please visit https://info.nopsema.gov.au/ 

The Offshore Petroleum and Greenhouse Gas Storage Act 2006 requires a titleholder to remove all property within the title area that is neither used nor to be used in connection with the operations authorised by the title, or implement an approved alternative. Government policy and guidelines allow in situ decommissioning if it achieves equal or better environmental outcomes compared to complete removal, and if it meets requirements including well integrity and safety.

Chevron proposes leaving the well infrastructure in situ.

Leaving the wellhead in situ has the potential for environment interactions, known as ‘aspects’.

‘Aspects’ may present environmental risks within the operational area if left unmanaged. Table 1 lists the potential environmental impacts, risks and control measures.
There is no emergency condition associated with leaving the wellhead in situ because it has been plugged and abandoned.

For the purpose of the Environment Plan, the environment that may be affected (EMBA) has been defined as a 500m radius around the wellhead. Corrosion of the wellhead is expected to result in a smaller footprint where seabed disturbance may occur due to the presence and breakdown of the wellhead and release of breakdown product (mostly iron).

There is no exclusion zone, and this is not intended to change.

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, provide an assessment of the potential environmental impacts and risks arising from the activity, and identify control measures to manage environmental impacts and risks to acceptable levels that are as low as reasonably practicable.

The Environment Plan 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 1.

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.