The Longtom gas field, located in production licence VIC/L29, lies approximately 30km south west of Marlo in East Gippsland, Victoria. Longtom was discovered in 1995, Longtom-3 was drilled in 2006, Longtom-4 in 2008 and gas production commenced in October 2009. The subsea facilities consist of the following:
• Two existing subsea wells Longtom-3 and Longtom-4, each located within a Petroleum Safety Zone (PSZ).
• A 17 km 300mm nominal diameter Longtom pipeline originating at the Longtom-3 well and connecting into the offshore end of the Patricia Baleen pipeline. The Longtom pipeline is covered by licence VIC/PL38.
• A subsea umbilical extension connected to the existing Patricia Baleen umbilical line that provides electrical, hydraulic and chemical services to the Longtom facilities.
From the commencement of production in 2009 the Longtom gas flowed to shore via the Patricia Baleen gas pipeline, and then to the Orbost Gas Processing Plant. In May 2015 an electrical fault in the offshore umbilical resulted in the loss of communications with the offshore facilities and led to an unplanned shutdown and the cessation of production. The Longtom-3 and Longtom-4 well valves and pipeline valves are all closed. An offshore campaign was undertaken in early 2017 to confirm the status of the subsea facilities and to rectify the electrical connection to the Longtom-3 well. Additional pipeline and subsea facilities inspections were carried out in 2023 and 2024. The results confirm that the well and pipeline valves remain closed isolating the Longtom pipeline from both the reservoirs and from the Patricia Baleen pipeline and that there has been no significant corrosion or disturbance to the Longtom facilities.
Periodic inspection, maintenance and repair (IMR) activities will require offshore vessel operations and this may include survey activities, ROV operations, diving, lifting and the installation of items such as concrete mattresses. Vessel operations for IMR activities are expected to be required for 1 week every year.
Planning is underway for the resumption of Longtom gas production, which may occur from 2028 onwards. After the restart of the offshore facilities, a future subsea well (Longtom-5) may be developed within the Longtom-3 PSZ and connect to the existing subsea facilities. If proceeding, the associated drilling and tie-in activities will be subject to a separate EP.