NOPSEMA has approved Santos WA Northwest Pty Ltd’s plan for the operation of subsea infrastructure and pipelines offshore Western Australia. Santos’ scope of the Varanus Island Hub Operations environment plan (EP) comprises activities that are associated with the operation of the John Brookes wellhead platform, associated subsea wells and pipelines.
The activities will occur in Petroleum Production Licences WA-29-L, WA-45-L and WA-13-L, approximately 127 km northwest of Karratha.
Ongoing inspection, maintenance, monitoring and repair within the operational area may include activities such as:
- General inspections;
- Integrity Corrosion control;
- Plant and subsea infrastructure cleaning, repair and modifications;
- Subsea pipeline and seafloor imaging surveys;
- Subsea Equipment and Infrastructure Installation, Cleaning, Repair and Modification;
- Marine growth removal;
- Inline inspections of pipelines (pigging);
- Installation of replacement equipment/parts;
- Installation of additional secondary stabilisation;
- Pipeline stabilisation;
- Topsides cleaning of facilities (both maintenance and for suspension); and
- Rigless well servicing or intervention.
Santos is the operator of the John Brookes and Greater East Spar gas fields located in offshore Commonwealth waters on the North West Shelf of Western Australia. Production fluids (gas and condensate) from these fields are transported by subsea pipelines (the John Brookes Pipeline and East Spare Pipeline) to the Varanus Island oil and gas hub located in State waters.
The John Brookes facility is located in approximately 45 metres of water. Production commenced in 2005, and the facility consists of:
- John Brookes wellhead platform (WHP) – a normally unmanned wellhead platform designed to accommodate a maximum of six production wells;
- John Brookes pipeline – a 55-km-long, routed to the Varanus Island onshore processing facilities; and
- John Brookes wells – four producing wells at the John Brookes WHP.
The John Brookes facility also provides infrastructure for the control of the Halyard and Spar-2 subsea wellheads. However, production from the Halyard and Spar wells is independent of the John Brookes facility, as Halyard well fluids are exported to Varanus Island via the 65km long East Spar pipeline.
Rosella-1 is an open-water, temporarily abandoned exploration well located approximately 12 km southwest of the John Brookes facility. Rosella-1 was plugged and temporarily abandoned at the time of construction in October 2007.
Varanus Island operators provide 24/7 control of the WHP via telemetry and a distributed control system from a central control building on Varanus Island. WHP visits are required for inspection, maintenance, monitoring and repair activities, with crews travelling via helicopter or support vessel to the WHP to carry out inspection, maintenance, monitoring and repair; to replenish fuel or chemicals; and to carry out operational requirements, such as a restart after a trip.
The approval and the EP explicitly excludes offshore drilling and decommissioning activities, which will require separate EPs when or if required.