John Brookes

Location

The John Brookes field is situated in the Carnarvon Basin, within exploration permits WA-214-P and WA-29-L, in Commonwealth waters. The field is approximately 110 km from the Western Australian mainland and 30 km northwest of the state waters boundary.

Discovery and Development

The John Brookes field was discovered in 1998 with the drilling of the John Brookes-1 well. Further appraisal was conducted with the drilling of the Thomas Bright-1 well in March 2003 and the Thomas Bright-2 well, which successfully appraised the southern area of the field in 2003. This second appraisal well increased the estimated gross 2P (proven and probable) gas volume from 400 billion cubic feet (BCF) to approximately 800 BCF.

Ownership and Operation

As of the development phase, the field was jointly owned by Santos Limited and Apache North West Pty Ltd. Santos held a 45% interest, while Apache, the operator, held a 55% interest. However, it is noted that Santos WA Northwest is currently operating the field.

Production

Gas production from the John Brookes field commenced in mid-2005. The field has recovered 88.58% of its total recoverable reserves as of the latest data, with peak production achieved in 2010. Production is expected to continue until the field reaches its economic limit in 2030. The field currently accounts for approximately 1% of Australia's daily gas output.

Infrastructure

The John Brookes platform is connected to the Varanus Island gas processing facilities via a single 55 km subsea pipeline. Gas from the field is processed on Varanus Island before being exported.

Commercial Agreements

A letter of intent was signed with Newcrest Mining Limited for the supply of 20 million cubic feet of gas per day over a 15-year period, with sales expected to commence in the fourth quarter of 2004.

Recent Activities

In 2019, Santos conducted pipeline flushing operations on the John Brookes export pipeline using seawater dosed with a corrosion inhibitor. This was part of routine maintenance to ensure the integrity of the pipeline.

In 2023, gas production was temporarily halted due to a leak detected on the main gas trunkline connecting the John Brookes platform to the gas processing facilities on Varanus Island. Production resumed after repairs, with a ramp-up to full rates expected shortly thereafter.

Environmental Context

The field is located in the North-West Marine Region, characterized by a dynamic oceanographic environment with strong tides, cyclonic storms, and long-period swell. The seafloor in the area is generally flat, unconsolidated, and sedimentary with occasional calcarenite rock outcrops. Environmental management plans are in place to mitigate potential impacts, including the use of corrosion inhibitors and ensuring no planned discharges of production fluids or chemically treated seawater into the marine environment.