Gorgon Gas Development: Backfill Fields Offshore Project Proposal

Overview

Chevron Australia Pty Ltd (CAPL) is the operator of the Gorgon Gas Development (Gorgon), one of Australia’s largest natural gas projects located off the northwest coast of Western Australia. The first stage of Gorgon was the Gorgon Foundation Project (GFP), which included constructing the Gorgon Gas Treatment Plant (GTP) and domestic gas plant on Barrow Island and developing the Gorgon and Jansz–Io offshore gas fields. The initial Gorgon approvals process envisaged the development of other ‘backfill’ fields in the Greater Gorgon Area once production from the Gorgon and Jansz–Io fields began to decline. A backfill field is a supply of natural gas that is required to maintain the throughput to an operating facility.

CAPL proposes to undertake the Gorgon Gas Development Backfill Fields (the Development), which represents the next phase of Gorgon. The intent of the Development is to maintain gas supply to the existing gas plants on Barrow Island to sustain current production rates of liquefied natural gas (LNG) and domestic gas. The development of backfill fields will not extend the life or capacity of the Gorgon Gas Facility beyond the existing approvals.

The Development proposes to tie seven backfill fields into the existing subsea gathering infrastructure, which connects the two currently operational gas fields, Gorgon and Jansz-Io, with the Gorgon Gas Facility. Field development will be staggered, so all fields will not be developed in a single campaign.

The seven fields are located about 200 kilometres north of Onslow and 100 kilometres north-northeast of Barrow Island, at depths of 150 metres to 1,400 metres. Most of the fields are in water depths greater than 800 metres. The fields are: Chandon, Chrysaor, Dionysus, Eurytion, Geryon, Semele and West Tryal Rocks which are located across WA-5-R, WA-14-R, WA-15-R, WA-20-R, WA-21-R, WA-22-R, WA-53-R, WA-75-R and WA-76-R. The operational area includes a five-kilometre buffer around the most conservative indicative location of the backfill fields’ infrastructure.

Planned activities include:

• Conducting geotechnical and geophysical surveys.
• Drilling wells.
• Installing a subsea gathering network that connects the wells to the existing Gorgon and Jansz-Io pipelines.
• Commissioning and start-up.
• Operating the facilities including inspection, maintenance and repair.
• Operating vessels, helicopter and remotely operated vehicles.
• Decommissioning.

No permanent structures will be above the sea surface.

Activities to start the development of the first field are proposed to commence in 2026. The order of the development of the seven fields has not yet been finalised. However, subject to relevant approvals, Geryon and Eurytion have been earmarked as the next fields to be developed and are anticipated to be co-developed and use common infrastructure.