Chevron Australia has made its 14th discovery offshore Western Australia in 3 years with the drilling of its Pontus-1 wildcat in production licence WA-37-L. The well encountered a 30-m net natural gas pay zone.
The discovery well, drilled in 210 m of water, is in the same licence as Gorgon field, one of the mainstays of the Gorgon-Jansz LNG project. It lies about 65 km northwest of the LNG plant being constructed on Barrow Island.
The find will undoubtedly support potential future expansion opportunities for the LNG development.
Earlier this year Chevron, which is operator of the project, said it planned to begin front-end engineering and design studies for a fourth train on Barrow that would take the project capacity to 20 million tonnes/year (tpy) of LNG. The company also has pointed out that there is space within the Barrow Island precinct for a fifth train—something which is looking more and more possible with each discovery well.
The initial three-train Gorgon-Jansz project is a careful balance of carbon dioxide levels in the produced gas. Jansz has reserves of 20 tcf of gas and is the largest gas field found in Australia. It is double the size of nearby Gorgon, which has slightly less than 10 tcf. Significantly, it also has low CO2 content at less than 1%.
Gorgon contains closer to 14% CO2 and this factor presented one of the main stumbling blocks to at least two attempts to develop the field during the 1980s and 1990s.
When the Gorgon-Jansz project comes on stream in late 2014, the volumes of CO2 produced will total up to 300 MMcfd. This gas will be pressured into a semiliquid state for injection via an initial nine dedicated wells into the Dupuy formation aquifer deep beneath Barrow Island.
Chevron will endeavour to remain at or under these CO2 production levels even though it plans to expand the project with a fourth and probably fifth train in the future.
It will require a third offshore pipeline to bring in gas from a number of other fields already discovered in the Greater Gorgon area. Construction of Train 4 is pencilled in for a start in 2014. The fields most likely to be considered for this expansion are Yellowglen, Chandon, Satyr, Achilles, Maenad, Orthus, Urania, Geryon, Dionysus, Dionysus North, Chrysaor, and the original 1970s find at West Tryal Rocks.
These contain differing amounts of CO2 with finds like West Tryal Rocks at the high end and the newer discoveries north of Gorgon, such as Geryon and Urania, at the lower end.
Chevron has yet to name the specific fields for train four but has said it will opt to develop those with lower content CO2 in the next phase of development. It will leave development of the higher CO2 content fields until Gorgon moves into its production decline.
This sequential field management program is designed to maintain the important balance now provided to the Gorgon project by the Jansz connection.
Chevron has 47.3% of WA-37-L while ExxonMobil and Shell have 25% each. Osaka Gas, Tokyo Gas, and Chubu Electric Power hold respective interests of 1.25%, 1%, and 0.42%.
