Basin review, Markets, Offshore, Projects

Branching out in Bass Strait

The scope of ExxonMobil’s operations in Victoria’s offshore Gippsland Basin is vast. Approximately 7 trillion cubic feet (Tcf) of gas has been produced from 21 offshore platforms and installations in Bass Strait since Australia’s first offshore well discovered gas in the area in 1965.

Gas produced in the Bass Strait is piped to the onshore facilities at Longford, comprising three gas processing plants and one crude oil stabilisation plant.

ExxonMobil is expanding its gas operations in the area with the addition of the new Marlin B platform and Kipper subsea wells as part of the Kipper Tuna Turrum Development, which began construction in mid-2010.

As the project name suggests, three fields are being developed as part of the project.

Kipper

The Kipper field is a joint venture between ExxonMobil subsidiary Esso Australia Resources, BHP Billiton and Santos, and is located approximately 45 km off the Gippsland coast in 100 m of water. It is estimated to hold 620 billion cubic feet of recoverable gas. When complete, it will be able to produce 10,000 barrels per day (bbl/d) of condensate and 80 million cubic feet per day (MMcf/d) of gas.

To develop the field, subsea facilities including two wells, four coolers and a manifold will be tied back to the existing West Tuna platform. The tie-back pipeline will be a dual 350 mm diameter, 18 km pipeline and umbilical. A 450 mm diameter, 16 km pipeline will connect West Tuna to Marlin B, and a 450 mm, 18 km pipeline will connect Marlin B to the Snapper platform, for Kipper gas production and development of the Tuna gas cap. These subsea pipelines are in close proximity to existing pipelines.

Diamond Offshore’s Ocean Patriot drilling rig completed drilling of the Kipper wells in December 2010. Installation of the West Tuna to Kipper looping pipeline by combination pipelay construction barge DB30 began on 18 November 2010. Once this has been completed, DB30 will begin installing the West Tuna to Marlin B and Marlin B to Snapper pipelines, all of which is expected to be complete by the end of March 2011.

Construction of the new operations at Kipper is expected to be complete in 2012. These new operations form Stage 1A of the overall proposed development of the field. Stage 1B is planned to commence in 2014 and will include a further two wells. Finally, Stage 2 will see new gas compression services at the Gippsland Basin Joint Venture facilities in 2016 (or later).

Over the first four years after start-up of Stage 1A, Santos will lift 70 per cent of gas production, which is twice its working interest in the field.

Tuna

The Tuna field lies between the Kipper and Turrum fields. It currently produces oil. Tuna is a part of the Gippsland Basin Joint Venture, in which Esso Australia Resources as operator and BHP Billiton each have an equal share. The partners are now developing the field to produce gas and associated liquids. To do this, the existing West Tuna facilities will be converted and new pipelines will be installed to deliver production into the existing gas system.

Turrum

The Turrum field, currently producing via the Marlin A platform, holds approximately 1 Tcf of gas and 110 million barrels of oil and gas liquids. Turrum is also part of the Gippsland Basin Joint Venture. Upon completion, it will be able to produce 11,000 bbl/d of condensate and 200 MMcf/d of gas.

To produce additional oil and gas from the field, a new platform will be installed above the field. Marlin B, the first new platform to be installed in Bass Strait in over a decade, will be constructed and linked via a bridge to Marlin A. The new 3,750 square metre platform weighs 4,700 tonnes and is 45 m high.

The Marlin B jacket arrived at Western Port on a large heavy lift vessel in January, mooring just off Cowes, Phillip Island. After being lowered into the water, the jacket was towed to Corner Inlet, awaiting towing to Bass Strait for installation in March.

Following on from installing pipelines as part of the Kipper development, DB30 will secure the Marlin B jacket to the seabed, installing the modules onto the jacket and installing the linking bridge between Marlin A and Marlin B.

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