Overview of the 2014 offshore acreage release areas for petroleum exploration
Dr Thomas Bernecker
The latest offshore petroleum exploration areas have been formally released by the Minister for Industry Ian Macfarlane at the 2014 annual Australian Petroleum Production and Exploration Association (APPEA) conference.
The Australian Government's annual release of offshore petroleum exploration acreage encourages investment and contributes to the responsible development of Australia's oil and gas resources. In 2014, Minister Macfarlane has announced that 30 areas in ten offshore hydrocarbon provinces would be available for petroleum exploration in Commonwealth waters.
This year, the government has introduced cash bidding for four selected areas, while the work program bidding process continues to apply for the remaining 26 areas. Cash bid areas are designed to be small (1-3 graticular blocks in 2014), located near existing production or known accumulations, and are all covered by 3D seismic surveys. Importantly, cash bid areas are geologically supported by proven petroleum systems.
Closing dates for work program bid submissions are either six or 12 months after the release date, i.e. 2October 2014 or 2April 2015, depending on the exploration status in these areas and on data availability. The cash bid areas will be auctioned on 5February 2015.
The 26 work program Release Areas are located in Commonwealth waters offshore Northern Territory and Western Australia, and include one large frontier area covering the Eyre Sub-basin in the Bight Basin (Figure1). The four cash bid Release Areas-three in the Northern Carnarvon Basin and one in the Caswell Sub-basin of the Browse Basin-are located adjacent to either producing fields or petroleum accumulations under development.
The invitation to submit industry nominations for vacant acreage to be gazetted was again widely accepted with all Release Areas nominated by industry supported. This indicates that the industry remains vibrant and confirms the ongoing interest to explore Australia's producing and frontier basins.
It is not surprising that the North West Shelf hosts the majority of the 2014 Release Areas given the sustained strong exploration activities across the Westralian Superbasin which extends from the Northern Carnarvon to the Bonaparte Basin along Australia's northern margin.
The Bonaparte Basin is represented by five Release Areas located on the Sahul Platform and Calder Graben, in the Petrel Sub-basin and in the northern Vulcan Sub-basin. The Vulcan Sub-basin is a proven oil and gas province, while much of the Bonaparte Basin hosts several commercial gas accumulations. Over the last decade, exploration has continued in the Bonaparte Basin, with between three and ten wells drilled per year. Currently there is increased industry focus on the commercialisation of existing discoveries as indicated by the number of extension/appraisal and development wells drilled, reflecting the maturity of exploration within the basin.
The Browse Basin is one of Australia's richest offshore hydrocarbon provinces. The Caswell Sub-basin hosts significant amounts of gas, condensate and, to a lesser extent, oil and four development projects are currently proposed or are in development phases. These are: the Prelude Floating Liquefied Natural Gas (FLNG) Development (encompassing the Prelude and Concerto accumulations), the Ichthys FPSO project and pipeline, the Browse Liquefied Natural Gas (LNG) Development (encompassing the Torosa, Brecknock and Calliance fields), and the Crux Liquids Project.
This year, a total of eight areas have been released in the Browse Basin, of which three are located in the northern basin, straddling the boundary to the Vulcan Sub-basin, and five in the centre of the Caswell Sub-basin. One of the areas, comprising two graticular blocks, has been released for cash bidding and is located in close proximity to the Ichthys and Prelude/Concerto gas accumulations.
The Northern Carnarvon Basin is Australia's most prolific hydrocarbon-producing basin accounting for nearly two thirds of the national gas production in 2011-12. Most of the offshore part of the basin in Commonwealth waters is currently under permit. The 15 Release Areas, including three areas for cash bidding, are spread across the Exmouth Plateau in deep water parts of the basin, and further inboard along the Rankin Platform and in the shallow water Barrow Sub-basin. Over the last decade there has been increasing focus on the commercialisation of existing discoveries in the basin with new pipelines built and additional ones planned. The application of new geophysical techniques and improved 3D-seismic data processing and imaging has contributed to a significant increase in the exploration success rate.
In the context of the recent award of seven large exploration permits linked to extensive work programs in the Bight Basin (Ceduna-Sub-basin), the Australian Government this year released one large (360 graticular blocks or 25,765km2) area that covers the entire Eyre-Sub-basin. The Eyre-Sub-basin is an offshore frontier over which 2D seismic data of variable quality was acquired and only one exploration well, Jerboa1, was drilled. Although no significant hydrocarbons were recorded during drilling, later analysis of oil in fluid inclusions in Upper Jurassic sandstones at the base of the well resulted in the identification of a 15 metre paleo-oil column. This provides evidence that hydrocarbons have migrated through the area in the past, suggesting an active petroleum system is present in the sub-basin. Therefore the large 2014 Release Area offers the opportunity to evaluate the occurrence and distribution of petroleum systems elements in a distinct depocentre along Australia's southern margin.
Geoscience Australia supports these industry exploration activities and provides open access to comprehensive pre-competitive geological and geophysical data gathered and collated by Geoscience Australia. This data helps industry to make informed investment decisions in relation to its exploration programs.
A new publication by Geoscience Australia, the Petroleum Geology Inventory of Australia's Offshore Frontier Basins, has also been made available to coincide with this year's APPEA Conference. The inventory presents a comprehensive inventory of the geology, petroleum systems, exploration status and data coverage for 35 frontier basins, sub-basins and provinces located on Australia's continental margin. The inventory is available for download from Geoscience Australia's website.
Other new Geoscience Australia products include a new set of biostratigraphic charts for the Bight, Browse and Bonaparte basins, and preliminary versions of the newly developed digital dataset of the offshore petroleum block framework and the National Offshore Petroleum Information Management System (NOPIMS) will also be on display.
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