jansz-io subsea compression installation

Chevron Australia, on behalf of the Gorgon Joint Venture, operates the Gorgon Project (Gorgon) in Western Australia.

Gorgon comprises offshore production wells and pipeline infrastructure that gathers natural gas from the Jansz-Io and Gorgon gas fields and transports it to a facility on Barrow Island for processing.

To maintain long-term gas supply to the facility, Chevron Australia plans to install a subsea compression station (SCSt) and associated infrastructure in the Jansz-Io gas fields, using proven subsea compression technology to enhance the recoverability of gas. The SCSt includes two pumps and three compressors and will be placed on ‘mud mats’ on the seabed.

Following consultation in 2023 and early 2024, Chevron Australia submitted State and Commonwealth Environment Plans (EPs) for Jansz-Io Compression (J-IC) installation activities. The Gorgon Gas Development Pipeline and Subsea Infrastructure Installation and Pre-Commissioning EP was accepted by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) in May 2024. The Gorgon and Jansz Feed Gas Pipeline - Umbilicals Installation EP was approved by the Department of Energy, Mines, Industry Regulation and Safety (DEMIRS) on 10 October 2023.

Jansz-Io Compression installation activities were scheduled to occur from mid-2024 to mid-2026.

As of December 2024, the indicative installation schedule has been updated, with activities now expected to occur from late-2024 to mid-2027. 

Table 1 provides details on the expected timing of activities.

Chevron Australia is committed to ongoing consultation and will provide updates where relevant persons would like to be kept informed on the timing of activities.

Activities include installing, pre-commissioning and commissioning of subsea compression infrastructure and a floating field control station (FCS).

Non-invasive surveys may be conducted before and after installation, including video and geophysical survey techniques. Helicopters and installation and support vessels will be used throughout the works.

Chevron Australia plans to install the following:

• Subsea structures, including a SCSt, subsea compression manifold station (SCMS) and associated foundations.
• A normally unattended, floating FCS moored to the seabed.
• An umbilical to supply power from Barrow Island to the FCS, and umbilicals from the FCS to subsea structures.
• Pipeline crossings and rock stabilisation as required.

The new umbilical will be installed adjacent to the existing offshore Jansz-Io feed gas pipelines. On Barrow Island, the umbilical will be installed in a trench within the approved right of way for existing infrastructure.

The shore crossing for the umbilical will be undertaken by horizontal directional drilling from a site to be established approximately 150 m inland from North White’s Beach, extending under the beach to approximately 550 m offshore, to avoid disturbing foreshore vegetation and the nearshore marine environment.

Table 1 includes details on the infrastructure to be installed.

As part of our environmental assessment and consultation process, we create an EMBA map to provide geographical context for stakeholders to determine if their functions, interests or activities may be affected by an offshore activity during operations or in an emergency scenario.

Figure 1 shows the EMBA, which is based on a worst-case environmental scenario, which in this case is an unplanned release (oil spill) from a vessel collision.

The EMBA has been defined through combining 300 simulations of vessel collisions under different weather and ocean conditions. This means that in the highly unlikely event an unplanned release does occur, a geographical area much smaller than the EMBA would be affected.

The majority of the impacts or risks directly arising from activities, or from an emergency scenario, would occur within close proximity of the Operational Area (OA).

Chevron Australia has systematic control measures to prevent and mitigate emergencies and to reduce the impact of planned activities on the environment, including ecological, social and cultural sensitivities.

Table 2 summarises the key impacts or risks and proposed control measures to manage these to levels that are as low as reasonably practicable (ALARP) and acceptable. 

During installation of the infrastructure, notices to mariners will be sought, to advise vessels to navigate with caution. A temporary 500-metre exclusion zone will be in place around vessels engaged in installation activities.

There is currently no exclusion zone over the existing infrastructure at the J-IC location. 

Once installed, a 500-metre exclusion zone will be in place for the floating FCS, however, no other exclusion zones will be sought for the subsea infrastructure.

We acknowledge that Traditional Owner groups in the northwest region of WA have identified Sea Country as an important value and expressed a deep obligation to protect songlines, dreaming stories and the marine fauna connected to them.

Chevron Australia is committed to ongoing engagement and consultation with Traditional Owners and their representative bodies. This process will continue to inform our understanding of cultural values and features and help facilitate the co-design of appropriate controls to avoid impacts.

In accordance with the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations 2023 (Cth), the installation of the J-IC infrastructure in Commonwealth waters requires an EP to be submitted to NOPSEMA for assessment and acceptance. These regulations require Chevron Australia to consult with relevant persons whose functions, interests and activities may be affected by the petroleum activity.

Installation activities in State waters and onshore are regulated by DEMIRS and are addressed in an EP in accordance with the requirements of the Petroleum (Submerged Lands) (Environment) Regulations 2012 (WA) and the Petroleum Pipelines (Environment) Regulations 2012 (WA).

Both EPs describe the environment in which the installation activities are planned to take place, provide an assessment of the impacts and risks arising from the activities, and identify control measures to manage the potential impacts and risks to levels that are ALARP and acceptable.

The EPs also outline how Chevron Australia has engaged with ‘relevant persons’, whose functions, interests and activities may be affected and how their feedback has been considered and addressed.

A summary of impacts/risks and key proposed controls for installation activities can be viewed in Table 2.

We are committed to engaging with Traditional Owners and Custodians, commercial fishers, recreational groups and other relevant individuals and organisations, as required by regulation.

The initial consultation period has concluded, however we are now seeking your feedback if you consider your functions, interests, or activities may be affected based on the updated installation schedule outlined in Table 1.

 You can contact us with any questions, requests for information, or feedback by calling tollfree on 1800 225 195 or online below.

Relevant persons may request that the information they provide be treated as confidential. Chevron Australia will make this known to NOPSEMA and it will be identified as sensitive information and not published in the EP.

Chevron Australia has notified relevant persons of the change in the indicative installation schedule.

We are now accepting feedback and input until 17 February 2025.

We commit to keeping you informed and providing responses to any relevant person who so request.

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.