The Otway gas project comprises the Thylacine and Geographe gas fields in the offshore Otway Basin and the onshore Otway gas plant located near Port Campbell in south-west Victoria, Australia.

Beach Energy, an oil and gas exploration and production company based in Australia, operates the project with 60% interest. The remaining 40% is held by O.G. Energy Holdings, a subsidiary of Ofer Global group.

Discovered in 2001, the Thylacine and Geographe gas fields have been operational since 2008 and 2013, respectively. Beach Energy became the operator of the Otway gas project by acquiring Lattice Energy, a wholly-owned subsidiary of Origin Energy, in 2018. O.G. Energy acquired 40% interest in Beach Energy’s Victorian Otway assets in May 2019.

An expansion drilling campaign has been underway in the offshore Otway Basin since February 2021 to maintain production levels of the Otway gas plant. The drilling campaign is expected to be completed in December 2022.

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Location

The Thylacine and Geographe fields are located in the Otway Basin, which extends from Cape Jaffa in South Australia to north-west Tasmania.

The Thylacine and Geographe fields are located 70km and 55km off the coast of Port Campbell, Victoria, Australia, respectively. Water depths in the Thylacine and Geographe field areas are 100m and 85m, respectively.

Thylacine and Geographe field development details

The Thylacine field consists of four gas production wells, namely TA-1, TA-2, TA-3 and TA-4, and the unmanned Thylacine-A production platform operated from the Otway gas plant.

The gas output of the field is sent through a 69km-long and 20in-diameter subsea pipeline from the Thylacine-A platform to the shore crossing and further transported through the 11km-long, 20in-diameter onshore Otway Gas Pipeline to the Otway gas plant.

The Geographe field comprises a subsea production well (GEO-2) connected to a subsea manifold. The Thylacine-A platform and the Geographe manifold are connected through an umbilical system.

A flowline exports the wellstream from the manifold to the same subsea pipeline being used by Thylacine field to transport gas to the shore for processing at the Otway gas plant.

Otway Basin expansion drilling details

The ongoing drilling programme at the Otway Basin involves drilling two new Geographe production wells and four new Thylacine production wells, apart from drilling new exploration wells in the area. The drilling campaign started with spudding the Artisan-1 discovery well in February 2021.

The installation of subsea infrastructure for Geographe-4 and Geographe-5 production wells was completed in December 2021. The two new Geographe wells are expected to commence production in 2022.

The Ocean Onyx semi-submersible rig was drilling the Thylacine North-1 well, located 66km south of Port Campbell, as of December 2021. The drilling campaign at the Thylacine field is expected to be completed by December 2022. The four new Thylacine wells are expected to commence production in 2023.

Otway gas plant details

The Otway gas plant, located 7km north-east of Port Campbell, processes raw gas from the Thylacine and Geographe offshore gas fields, as well as the Halladale, Black Watch and Speculant nearshore gas fields operated by Beach Energy.

The raw gas is processed in the gas plant to remove carbon dioxide (CO2), water, hydrogen sulphide and other impurities. The gas plant produces natural gas as well as stabilised condensate, propane and butane.

The plant has a maximum operating capacity of 205 terajoules a day. It is designed to produce 60 petajoules of natural gas, 100,000 tonnes of liquefied petroleum gas (LPG) and 800,000 barrels of condensate a year.

Halladale, Black Watch and Speculant (HBWS) fields details

The Halladale, Black Watch and Speculant  fields are located 5km away from the shore in 40m-deep waters. A 33km-long and 219.1mm-diameter underground pipeline transports the wellstream from the HBWS wellsite to the Otway gas plant.

The Halladale and Speculant fields commenced gas production in 2016, whereas  the Black Watch-1 gas development was connected to the Otway gas plant in 2020. The Black Watch-1 well with a measured depth of 7.2km is claimed to be the longest well ever drilled in Australia using an onshore rig.

The Halladale and Black Watch gas fields were discovered in 2005, whereas the Speculant field was discovered in 2014.

Enterprise and Artisan discoveries

The Enterprise-1 gas discovery in the nearshore Victorian Otway Basin was announced in November 2020. The discovery well was drilled through extended reach drilling (ERD) technique from an onshore location 3.5km away from Port Campbell. The well encountered 115m of net gas pay in the Upper Waarre Formation.

The Artisan-1 gas discovery located 30km offshore in the Victoria Otway Basin was announced in March 2021. Drilled by the Ocean Onyx rig, the well encountered 62.9m of net gas pay in the primary Upper Waarre Formation and 4.6m of net gas pay in the overlying Flaxman Formation.

Contractors involved in Otway gas project expansion

DOF Subsea Australia bagged a contract to manufacture, transport and install the subsea infrastructure for four new Thylacine production wells in December 2021. The subsea infrastructure includes umbilicals, flexible flowlines, connectors and rigid spools.

DOF Subsea’s construction support vessel SkandiAcergy will be deployed to execute the installation works. The company was also previously contracted for subsea installation works related to the two new Geographe wells in November 2020.

Diamond Offshore General Company was contracted to deploy Ocean Onyx semi-submersible rig to drill up to nine wells as part of Beach Energy’s Victorian Otway offshore drilling programme in August 2020.

Ensign Energy’s Ensign Rig 931 drilled the Black Watch-1 well and the Enterprise-1 gas discovery well.