Otway Basin

The Otway Basin can be broadly divided into two major structural elements; the onshore and offshore areas. The two areas are separated by major structural hinge zones of the Tartwaup and Mussel fault zones. The offshore part of the basin covers an area of about 92,000 km2

History

Offshore petroleum exploration began in 1967 with a four well campaign that discovered minor gas shows. A second phase of drilling up to 1975 resulted in seven dry holes. After further drilling with minimal results the first offshore discovery was made by BHP at La Bella in 1993. BHP had further success with the Minerva gas discovery in the same year. The most successful exploration campaign occurred during the 2000’s where drilling of seismic-amplitude supported prospects resulted in commercial gas discoveries at Thylacine, Geographe, Casino, Henry, Netherby, and Halladale/Blackwatch, as well as a sub-commercial discovery at Martha. Later drilling in the nearshore area (within 3 nautical miles of the coastline) by extended reach drilling from onshore resulted in the discovery of the Speculant field. In the offshore Otway Basin, all commercial fields have been discovered within or on the flanks of the Shipwreck Trough depocentre.

Onshore exploration for hydrocarbons commenced very early on with Salt Creek-1 drilled in SA in 1890. Although not strictly within the limits of the Otway Basin, it was the first of many wells drilled in the South East of South Australia and southwestern Victoria searching for oil and gas. The first commercial discovery of gas in the onshore Otway Basin was made by Beach Petroleum in 1979 at North Paaraatte-1 in the Port Campbell Embayment. There followed a succession of discoveries over the next few years which resulted in the Iona gas processing plant being built and gas piped to Melbourne.

In South Australia the first commercial hydrocarbon discovery was made in the Penola Trough at Katnook-1 in 1987. Further drilling resulted in other gas discoveries, resulting in the Katnook Gas Plant being constructed and gas piped to local industries, the township of Mt Gambier and the Ladbroke Grove Power Station. There has been very little drilling activity in the onshore Otway Basin over the last 10 or so years however, a recent gas discovery at Haselgrove-3 proves that the area is still prospective. Discoveries in the onshore Otway are smaller than the offshore discoveries. 

Geology

The Otway Basin formed as part of the Southern Rift System that extended across Australia’s southern margin as a result of tectonic separation of Australia and Antarctica. Rifting in the Late Jurassic-Early Cretaceous formed a series of broadly northwest-southeast striking depocentres, including the Penola Trough in South Australia. Fluvial-lacustrine Late Jurassic, Early Cretaceous and Late Cretaceous sediments fill the asymmetric graben of the Penola Trough with sediments thinning onto the north-eastern flanks and thickening in a south-westerly direction towards the main fault controlling the asymmetric graben, the Kalangadoo Fault. The oldest sediments of the trough, the Casterton Formation, is interpreted to be the source of hydrocarbons produced to date as are the oldest sediments of the overlying Pretty Hill Formation. The Early Cretaceous aged Pretty Hill Formation also contains proven reservoir rocks.

A second Late Cretaceous rift event formed the main depocentres in the offshore area. The Shipwreck Trough forms the main proven hydrocarbon-generating depocentre in the offshore part of the Otway Basin. The Shipwreck Trough is a complex, fault-bound depocentre filled with fluvio-deltaic and marine sediments of the Sherbrook Group. The main source interval is coals of the Early Cretaceous Eumeralla Formation which are deeply buried with the trough. The basin features a series of proven, productive Cretaceous-aged sandstone reservoirs. These include the Waarre Formation, Flaxman Formation and Thylacine Member. Gas fields in the offshore area commonly feature more than one reservoir interval. 

Haselgrove-3 Conventional gas well - (South Australia PPL 62)  

Drilling of Haselgrove-3 is being supported by the South Australian Government through the Plan for Accelerating Exploration gas grant scheme, which aims to bring new gas to market within three years. Under the terms of the $6 million grant, if a discovery at Haselgrove-3 is deemed to be commercial, Beach will enter bilateral negotiations with prospective South Australian customers for supply of gas at prevailing market terms.
 
For more information please see:

Media Release - Protecting the States Groundwater - 20 July 2017 – 

Media Release - Haselgrove-3 location - 11 July 2017 – 

Media Release - 24 May 2017 – 

Media Release - 17 March 2017 –

ASX Release –

Haselgrove-3 Fact Sheet –

Haselgrove-3 Frequently Asked Questions –

Community Engagement

Community engagement will be a focus of our program.  Please keep an eye on this page for information about upcoming community information sessions in the South East.  In the mean time if you would like to speak to Beach about the project please contact:

Group Executive Exploration and Appraisal – Jeff Schrull
Regional Manager South East - Glenn Toogood

Email:      info@beachenergy.com.au
Phone:     08 8338 2833

Public information sessions 

Public Information Sessions –

Other useful information

Otway Basin –Environmental Impact Report –

Statement of Environmental Objectives –

Beach Energy Sustainability Report FY16 –

For more information the petroleum industry regulatory processes please visit the Department of State Development at:
http://petroleum.statedevelopment.sa.gov.au/

For more information about the oil and gas industry please visit:
https://www.appea.com.au/