Our subsea gas-gathering system will be located on the ocean floor over the Gorgon gas fields west of Barrow Island in 200 to 1,300 meters (656 to 4,265 ft) of water.
Key components of the subsea gathering system include:
Development Wells
It is anticipated that between 20 and 30 wells will be drilled in the Gorgon area gas fields over a 30-year period.
The number of development wells and timing of construction will depend on future gas demand.
Wells will be drilled in campaigns to optimise the efficiency of rig operations and minimise mobilisation/de-mobilisation costs.
Offshore support during the drilling campaigns will be from an onshore support base located on the mainland.
Subsea Trees
Subsea trees provide containment to, and control of, production wells and would be connected to cluster manifolds via well jumpers all located on the ocean floor.
Subsea trees are installed by the drilling rig during well completion operations.
Cluster Manifolds
Fluids from up to eight wells would flow to each cluster manifold located near on the ocean floor.
These cluster manifolds gather fluids from the wells into a single flow path for connection via jumpers to the pipeline termination structures.
Flowlines
Flowlines of various sizes would connect the pipeline termination structures together and ultimately form the conduit for produced fluids to the LNG plant on Barrow Island.
Some of the flowlines will be made of corrosion resistant alloys depending on their function.
Control System
An electro-hydraulic multiplexed control system with primary fibre optic communications will allow monitoring and control of the subsea equipment via umbilicals tied back to the onshore LNG plant.
We’ll be using corrosion-resistant alloys and chemical corrosion management techniques to counteract the corrosive nature of the produced fluids.
Normal operation of the wells and subsea facilities would be remotely controlled from the gas processing facility on Barrow Island.
Requirements for offshore support, like the provision of construction materials and maintenance, would be provided from a mainland support facility – ensuring offshore construction and maintenance does not effect on the Barrow Island environment. Remotely operated vehicles, offshore work vessels and semi-submersible drilling rigs would be used for inspection and maintenance of the subsea system.