The Otway Basin is a rift basin which is located in on/offshore South Australia, Victoria and Tasmania. It extends for 500 km between from just west of Melbourne to Cape Jaffa in South Australia and to just north of King Island in the south. Major currently producing projects in the basin are all situated offshore Victoria/Tasmania and include Lattice Energy's (Beach Energy) Otway Gas Project (Thylacine and Geographe fields) and Halladale, Blackwatch and Speculant fields, Cooper Energy's Casino, Henry and Netherby fields and BHP's Minerva field (near depletion). Gas has also been produced from the Katnook, Ladbroke Grove and Haselgrove fields in the Penola Trough, onshore South Australia. The basin is relatively under-explored by international standards, with potential for further conventional and unconventional gas discoveries in the Penola Trough and offshore area of the basin.
Currently, the basin is serviced by three main processing facilities near Port Campbell in Victoria (Otway Gas Plant, Minerva Gas Plant and Iona Gas Plant). The Katnook Gas Processing Plant is located near Penola in South Australia and is connected to various industries in the region and to Mt Gambier. All facilities are connected to the SEA Gas Pipeline which sends gas to both Melbourne and Adelaide.
The Katnook plant was built and commissioned in 1991 and subsequently over 70 Bcf of gas and 0.4 MMbbls of condensate has been produced from the Pretty Hill Sandstone reservoir and supplied to local industry and the adjacent Ladbroke Grove Power Station, which was commissioned in 2000. All Penola Trough fields are currently shut in. The plant and fields are owned and operated by Beach Energy (100%).
Vintage Energy acquired a working interest in PEL 155 in the Otway Basin by way of a staged farm-in agreement with Rawson Oil and Gas Ltd. The Joint Venture is working towards drilling a gas exploration prospect (Nangwarry-1) located in PEL 155, approximately 10 kilometres southeast of the Katnook Gas processing facility (operated by Beach Energy).
Under the terms of the agreement:
The South Australian Government's second round of PACE Gas Grants is an initiative designed to further accelerate investment in gas projects in South Australia through targeted competitive grants. The $4.95 million grant will be applied to the drilling of Nangwarry-1. Vintage and Rawson will contribute to the cost of drilling Nangwarry-1 on 50:50 basis and the grant proceeds will be shared on the same basis.
The prospect is a three-way dip, fault dependent trap in the Pretty Hill Formation and is defined on 3D seismic. It is considered analogous to the nearby Katnook, Haselgrove and Ladbroke Grove fields which have produced substantial quantities of gas since discovery. A recent re-evaluation of existing 2D and 3D seismic identified four additional conventional leads, providing attractive follow-up targets in the event of a discovery.
The Nangwarry prospect has been greatly enhanced by the new field discovery in the Sawpit Sandstone made by Beach Energy at Haselgrove‑3/ST-1. This well was drilled in an adjacent licence by Beach Energy during late 2017 and is located approximately 8 km to the north of the proposed Nangwarry-1 location. Beach Energy reported (ASX, 11th January, 2018) a gas column extending over a gross interval of 104 metres of which 25.6 metres is net gas pay. The well was production tested and flowed at a tubing constrained rate of 25 MMscf/day through a 36/64” choke at a well head pressure of 2,700 psig. In addition, a gross gas column of 11.6 m was intersected in the shallower Pretty Hill Sandstone, with estimated net pay of 8.5 m. This well represents a significant, new play discovery with an extensive gas column and should provide much incentive for a renewed phase of exploration in the region.
Deepening of the proposed Nangwarry-1 well will target the Sawpit Sandstone in addition to top Pretty Hill Sandstone.
Drilling success will extend both a proven play province and the new Sawpit Sandstone play province, provide much needed gas to the South Australian market and increase exploration in the region. Ultimately, it is hoped continued investment will lead to a rebuild of the gas industry in the South East of South Australia, provide stimulus to industries in the region and alleviate issues of gas supply for power generation and other industries in South Australia. Gas supply opportunities exist via pre-existing pipeline networks connecting local industries and the eastern states gas supply network.
The Joint Venture looks forward to working with the Government of South Australia, local industry and the communities of the South East to progress this exciting conventional gas exploration drilling opportunity.
Vintage has executed a binding Heads of Agreement with Somerton Energy Pty Ltd (‘Somerton’, a wholly owned subsidiary of the ASX-listed Cooper Energy Limited) dated 17 April, 2018 to farm-in to PEP 171.
Somerton is awaiting Ministerial consent in Victoria to increase its interest in PEP 171 to 100%, following the withdrawal of Beach Energy Ltd. Vintage may then earn an initial interest of 25% by bearing all costs associated with the permit through to the end of the moratorium period and undertaking a prospectivity review as permitted under the moratorium. Vintage has the right to acquire a further 25% interest (50% in total) by contributing 65% of the cost of a 100 km2 3D seismic survey up to an agreed cap.
PEP 171, comprising an area of 1,974 km2, was awarded in August 2013 for a period of 5 years. Following the first term there is a right to one renewal with a 50% relinquishment. Due to a series of suspension and extension applications, Year 1 has ended, with the timing for completion of the work programs in subsequent licence years yet to be determined by the regulator, due to the effect of the moratorium explained below.
Effective 16 March, 2017 the Victorian Government amended the Petroleum Act 1998 by enacting The Resources Legislation Amendment (Fracking Ban) Act 2017; the effect of which was to:
While unconfirmed, the obligations of the work program are effectively suspended and cancelled, to the extent of hydraulic fracturing, which had formed part of the Year 3 work program. For the interim, the holding costs are minimal and the expected remaining committed work program will be to acquire 100km2 of 3D seismic and drill one exploration well.
Following the results of the 2017 Haselgrove-3/ST-1 gas discovery attention has refocussed on the results of the Glenaire-1/ ST- 1 well drilled in PEP 171. This well encountered good gas shows in the Laira Formation and Pretty Hill Sandstone during drilling in 2006. A thickness of 8.8 m of net gas pay was interpreted in the Pretty Hill Sandstone and a test in the Laira Formation recovered 12 barrels of oil but the well was considered uncommercial. The plan is to correlate the existing seismic between Glenaire-1/ST-1 and Haselgrove-3/ST-1 and to the Nangwarry-1 well after drilling.
Nine leads are currently recognised which are primarily fault-bound, dip closures, however the seismic data quality is poor to average, particularly deeper in the section, requiring a 3D survey to identify the optimum drilling location.
The Joint Venture looks forward to working with the Government of Victoria, local industry and the communities in Western Victoria to progress this exciting conventional gas exploration opportunity.