Jansz-Io

Location

The Jansz-Io gas field is situated approximately 200 kilometers off the northwest coast of Western Australia, within production licenses WA-36-L, WA-39-L, and WA-40-L. It is 70 kilometers northwest of the Gorgon gas field, 140 kilometers northwest of Barrow Island, and 250 kilometers from Dampier.

Discovery and Drilling

The Jansz field was discovered in April 2000 by the Jansz-1 exploration well, and the adjacent Io field was discovered in January 2001 by the Io-1 discovery well. Further appraisal wells, including Jansz-2, Jansz-3, Jansz-4, Io-1, and Io-2, were drilled between 2000 and 2009 to delineate the field extent and characterize the resource.

Geology and Reserves

The Jansz-Io gas field is located in the Carnarvon Basin and extends over an area of approximately 2,000 square kilometers. The hydrocarbon trap is defined by both structural (faulted anticline) and stratigraphic (reservoir pinch-out) components. The field holds more than 40 trillion cubic feet (tcf) of gas, jointly with the Gorgon field, and is expected to have a production life of at least 40 years.

Development Details

The Jansz-Io field development is part of the Gorgon Project, which includes:

• Production Wells: The first phase involved the development of ten production wells, including the conversion of the existing Jansz-4 appraisal well to a pressure monitoring well. These wells were drilled from two drill centers using the Transocean Deepwater Frontier drillship.
• Subsea Infrastructure: The project includes a subsea tieback to the onshore LNG plant, an offshore feed gas pipeline system, a monoethylene glycol injection pipeline, and an electro-hydraulic control umbilical. Six product pipelines and two umbilical casings connect the operations to the west coast of Barrow Island.
• Processing Facilities: The gas is processed at a 15.6 million tonnes per annum (Mtpa) LNG plant, a domestic gas treatment plant, and a carbon dioxide sequestration facility on Barrow Island.

Production

The Jansz-Io field commenced operations in 2015, with the first LNG produced in March 2016. The field supplies gas to the Gorgon gas processing facilities on Barrow Island. The average daily production from the project includes 2.1 billion cubic feet (Bcf) of natural gas and 15,000 barrels of condensate as of 2020.

Jansz-Io Compression Project

To maintain long-term gas supply and address the expected decline in reservoir pressure from 2025 onwards, the Jansz-Io Compression (J-IC) project was initiated:

• Infrastructure: The project involves the construction and installation of a 27,000-tonne normally unattended floating Field Control Station (FCS), approximately 6,500 tonnes of subsea compression infrastructure, and a 135-kilometer submarine power cable linked to Barrow Island.
• Subsea Compression System: The system includes three compressor modules and two subsea pump modules, all-electric control systems, and a high-voltage electrical power distribution system.
• Power Supply: A 135-kilometer submarine cable and a 14-kilometer land cable will transmit power from Barrow Island to the floating field control station.
• Contractors: Aker Solutions, ABB, Baker Hughes, and Daewoo Shipbuilding & Marine Engineering (DSME) are among the contractors involved in the project.

Project Timeline and Costs

• Initial Production: The Jansz-Io field started operations in 2015.
• Compression Project Approval: The final investment decision (FID) for the Jansz-Io compression project was made in July 2021.
• Construction and Installation: The construction and installation activities for the compression project are scheduled from mid-2024 to mid-2026.
• Costs: The overall investment for the Gorgon Project is estimated at A$43 billion (approximately $36.5 billion), while the Jansz-Io Compression project is valued at approximately $4 billion (AU$6 billion).

Joint Venture Partners

The Gorgon Project, including the Jansz-Io field, is operated by Chevron Australia with a 47.3% interest. Other partners include ExxonMobil (25%), Royal Dutch Shell (25%), Osaka Gas (1.25%), Tokyo Gas (1%), and JERA (0.417%).

Environmental and Operational Considerations

The project includes measures such as carbon dioxide sequestration facilities and environmental protection measures to minimize the impact on the marine ecosystem. The recent Gorgon Stage 2 development also involved expanding the subsea gas gathering network to maintain feed gas supply for the processing complex on Barrow Island.