Woodside Petroleum Ltd. has released for public comment its draft environmental impact statement (EIS) for the proposed $30 billion (Aus.) Browse LNG project in Western Australia.
The project involves development of the Torosa (originally called Scott Reef), Brecknock, and Calliance (originally Brecknock South) gas-condensate fields found between 1971 and 2000 some 425 km north of Broome and 290 km off the Kimberley coast.
Collectively they are estimated to contain 13.3 tcf of recoverable gas and 360 million bbl of recoverable condensate. They lie in 400-700 m of water.
The EIS outlines a development that includes the drilling of 50-90 wells over the 50-year project life.
The wells will be connected to seabed manifolds (four at Torosa, the northern-most field, two at Calliance in the south, and one at Brecknock in the center) which in turn will each be connected through flowlines to their in-field platforms.
The field platforms will then be connected by subsea pipelines to a four-platform central processing facility closer to shore in 80-120 m of water.
Gas and condensate will be processed at this offshore facility before being sent by a 310-km trunk line to the LNG facility that will be built at the Western Australian government’s chosen LNG hub site at James Price Point some 60 km north along the coast from Broome.
Woodside notes in the EIS that most of the expected impacts of the scheme are classed as low risk, although local fisheries will face a medium risk through exclusion zones that will be placed around the platforms and drilling rigs. Even so, this total exclusion zone area will be small.
Tests to determine the impact of light from Torosa platform on marine turtles in an around Sandy Islet (which is the small surface expression of the nearby Scott Reef atoll) suggest that maximum light levels reaching the islet will be no more than a small lit object. This will not influence nesting behaviour of adult turtles.
Nevertheless, Woodside has begun a long-term monitoring program of turtles on the islet to identify any impacts from the proposed development.
The EIS also assessed noise levels produced during construction, vessel movements and operational activities. Most were found to be of low risk to cetaceans. The company will investigate insulation methods to reduce noise produced by fluids passing through the subsea choke valves.
In addition, the study looked at the potential for vessels and rigs introducing invasive species and the temporary changes in water quality due to elevated suspended sediment from pipeline trenching work.
Woodside said alternative development schemes were looked at and dropped. The Browse-to-Darwin pipeline option was too expensive. A liquefaction facility built on concrete foundations in the shallow water of the southern lagoon at Scott Reef was deemed environmentally unacceptable.
Floating LNG was dropped because of the need for multiple facilities to efficiently recover gas from the fields. Consideration of a Browse-to-Burrup Peninsula pipeline showed this to be the most viable alternative to James Price Point, but it raised the possibility of issues related to the cumulative impacts on the Burrup potentially presenting environmental challenges.
Overall the EIS represents 17 years of detailed research which Woodside says has shed new light on Western Australia’s northern offshore ecosystems.
Browse LNG is expected to contribute up to $50 billion (Aus.) to the Australian economy and create up to 8,000 jobs (6,000 onshore; 2,000 offshore) during the construction period.
The project is expected to produce 12 million tonnes/year of LNG. A final investment decision is scheduled for 2012 with the first LNG coming on stream in 2017.
The EIS will be open for public comment until Jan. 25, 2012.