Project Profile
Value: US$315 million
Location: Gippsland Basin, offshore south-east Australia.
Start-up Year: October 2009
Oil and gas reserves: 268 billion cubic feet (Bcf) of proven gas reserves and 2.8 million barrels of proven condensate reserves
Water depth: 56 m
The Longtom gas field lies in the Gippsland Basin, offshore south-east Australia. The field is situated in the exploration permit VIC / P54 at a water depth of 56m (185ft). Nexus Energy is the operator and owns 100% interest in the field. First production from the Longtom field began in October 2009 and US$315m was invested in its development.
Discovery of the Longtom field:
The Longtom gas field was originally discovered by BHP Petroleum in January 1995 with the drilling of the Longtom-1 / ST1. The well encountered dry gas. BHP declared the field non-commercial due to the poor quality of the reservoir. In 2004, Nexus drilled the Longtom-2St-1 well, encountering a 400m gas column in five distinct reservoir zones. The Ocean Patriot semi-submersible drilling rig drilled the Longtom-3 well from July to September 2006. The well flowed at a rate of 75 million standard cubic feet per day (MMscf), confirming the commercial viability of the field. It was suspended as a future producer.
Geology and reserves:
The Longtom field reservoir is of the Admiral Formation, belonging to the Emperor Subgroup. The field is estimated to contain 268 billion cubic feet (Bcf) of proven gas reserves and 2.8 million barrels of proven condensate reserves. Nexus\'s field development plan was submitted in June 2007 and was approved by the Australian government in September 2007. Nexus started drilling development well Longtom-4 in June 2008. The West Triton jack-up rig was contracted to drill the well to a total depth of 4,648m. The well was completed and successfully flow tested in September 2008. A 19km-long, 12in-diameter Longtom pipeline was laid at the field using the Aussie-1 pipelay barge. The pipeline is carbon steel concrete coated. Both the Longtom-3 and Longtom-4 wells were tied back to the pipeline and brought into production. In April 2010, production at the field was halted after low quantities of mercury were discovered in the gas produced from Longtom-4. Nexus invested US$2m in the installation of mercury removal equipment at the Patricia Baleen gas plant. Production at the field resumed in October 2010.
Longtom production and exports:
Gas is produced through two horizontal subsea wells and production trees installed at water depths of 51-57m. A high integrity pressure protection system (HIPPS) is installed near Longtom-4. Produced gas is transported by the Patricia Baleen offshore gas pipeline to the Patricia Baleen gas plant in Orbost, Australia. Gas and condensate are separated at the gas plant. Gas is transported to Melbourne and Sydney through the Eastern Gas Pipeline. The condensate is transported to Shell\'s refinery in Geelong, Australia. Nexus has signed an agreement with Santos for the sale of 333bcf of gas and four million barrels of condensate over the life of the field.
Contracts for Longtom:
Trident Darwin Offshore Logistics Base Joint Venture was awarded the contract to install all the pipes and umbilicals for the Longtom field. The HIPPS package and the Longtom-4 subsea tree were built by Cameron. The control umbilicals were fabricated by UK-based Duco.
Operators:
Nexus Energy: Operator with 100% interest
Contractors:
Cameron: Built of HIPPS package and the Longtom-4 subsea tree
Duco: Fabrication of control umbilicals
Trident Darwin Offshore Logistics (joint venture of Trident Australasia & Offshore Logistics Base): Installation of pipes and umbilicals.