Pluto LNG Project, Northern Carnarvon Basin, Australia

The Pluto LNG project is located 190km north-west of Karratha, Western Australia, in the Northern Carnarvon Basin.

The project is a joint venture between Woodside, the operator, which has a 90% interest, and Tokyo Gas (5%) and Kansai Electric (5%), who became project partners in January 2008 and who have 15-year sales agreements for the gas.

The project will process gas from the Pluto and neighbouring Xena gas fields.

Pluto gas is said to be naturally low in carbon dioxide; about 2%, which is less than much of the other gas in the region.

The Pluto LNG project was originally scheduled to begin production in 2010. In June 2011, however, Woodside announced that the field's first LNG would begin in March 2012 due to delays in completion of the Burrup LNG Park. The cost of developing the project also increased to A$14.9bn from A$12bn.

Geology of the Pluto field

The Northern Carnarvon Basin developed during successive periods of extension and thermal subsidence. The first phase, Silurian to Permian, developed as a series of intracratonic basins during the break-up of Gondwana along the western margin of Australia. Subsequent Early Jurassic extension initiated the four main depocentres – the Exmouth, Barrow, Dampier and Beagle sub-basins.

A third extension phase, in the Middle Jurassic, resulted in the seafloor spreading in the Argo Abyssal Plain to the north, and the fourth, Tithonian-Valanginian rifting phase led to the creation of the Gascoyne-Cuvier abyssal plains to the west and south.

The depocentres contain up to 15km of sedimentary infill. Triassic to Early Cretaceous deposition is dominantly siliciclastic deltaic to marine, whereas slope and shelfal marls and carbonates dominate the Mid-Cretaceous to Cainozoic section.

The carbonate-rich sediments were deposited as a series of northwestward prograding wedges as the region continued to cool and subside. This resulted in deep burial of the underlying Mesozoic source and reservoir sequences in the inboard part of the basin.

Almost all of the hydrocarbon resources are within the Upper Triassic, Jurassic and Lower Cretaceous sandstones beneath the regional Early Cretaceous seal.

Reserves

The Pluto field is estimated to contain a total dry gas recoverable reserve volume of 4.4 trillion cubic feet (tcf). Xena, the smaller of the two fields, has a reserve volume of 0.6tcf.

Pluto development

The initial phase of the Pluto project consists of an unmanned, remotely operated offshore platform in 85m of water, connected to five subsea big-bore wells on the Pluto gas field.

Gas will be piped to shore along a 180km, 36in pipeline to the new Burrup LNG Park, located between the North West Shelf Venture and Dampier Port.

The gas will be processed in a single LNG processing train, which has a forecast production capacity of 4.3 million tonnes a year. The gas will be stored in two LNG tanks, with a combined capacity of 240,000m³, and three condensate tanks, which will have a combined capacity of 130,000m³.

The Burrup LNG Park has been designed to aggregate gas from the Carnarvon Basin to support future LNG growth and create another domestic gas supply hub for Western Australia.

The total area of the Pluto leases is about 200ha, of which the plant and facilities will cover about 80ha. Site preparation works at the Burrup LNG Park began in 2007. Contractors for the work include Foster Wheeler WorleyParsons, based in the UK, for the front-end engineering and design, and EPCM; BGC Contracting, of Australia, for the preparation of the storage and export site; Leighton Contractors, of Australia, for preparation of the LNG train site; CB&I, based in the Netherlands, for the storage tanks; and Boskalis, of the Netherlands, for the dredging.

Offshore contractors include EOS, a joint venture between WorleyParsons and Kellogg Brown Root JV, for the front-end engineering and design of the platform topsides, substructure and production system engineering; JP Kenny and Atteris, both of Australia, for the flowline and trunkline engineering; Bredero Shaw, of the US, for the pipe coating; FMC Technologies, also of the US, for the subsea hardware; McDermott Industries, of Australia, for the platform and its installation; and Shenzhen Chiwan Sembawang, a Sino-Singapore joint venture, for jacket fabrication.

Pluto environment

Woodside is investing up to A$100m in a programme to offset reservoir emissions from the Pluto field.

The aim, the company says, is to make Pluto one of the most environmentally efficient LNG plants in the world.

The programme involves a A$25m investment for mallee tree plantings in 2008 and 2009, with an option to undertake additional plantings for another three consecutive years.

The Pluto project also involves the largest marine monitoring programme of its kind in the world, which aims to minimise the impact on marine life resulting from dredging activities.

Woodside has also committed to offset the project's impact to the marine environment through a biodiversity offsets programme.