Areas W07-1, W07-2 and W07-3

Londonderry High, Bonaparte Basin

Exploration History

Bonaparte Basin Exploration Overview

Offshore exploration of the Bonaparte Basin commenced in 1965 when regional aeromagnetic data were acquired. This was supplemented by regional seismic coverage acquired between 1965 and 1974. The first offshore exploration wells, Ashmore Reef 1 and Sahul Shoals 1, located on the Ashmore Platform, were drilled as stratigraphic tests. Although these wells failed to encounter hydrocarbons, they indicated that the Jurassic section is either thin or absent and that Triassic sandstones form potential petroleum reservoirs over much of the Ashmore Platform.

Between 1969 and 1971, seven wells were drilled in the offshore Petrel Sub-basin. This drilling campaign resulted in the discovery of the Petrel and Tern gas accumulations reservoired within the Late Permian Hyland Bay Formation, which constitutes a primary exploration target in the outboard Petrel Sub-basin.

In the early 1970s, exploration expanded beyond the limits of the Petrel Basin, into the Vulcan Sub-basin and onto the Londonderry High and Sahul Platform. Between 1971 and 1975, 24 wells were drilled—a further nine in the Petrel Sub-basin, four on the Sahul Platform, six in the Vulcan Sub-basin, two on the Londonderry High, and two on the Ashmore Platform. Several significant petroleum discoveries were made during this period including Puffin, Troubadour and Sunrise.

Between 1975 and 1982 relatively low levels of exploration drilling were recorded in the offshore Bonaparte Basin (a total of eight wells) due to disputation between Indonesia and Australia over sovereignty of the sea-bed boundary.

The discovery in 1983 of economic oil and gas in Jabiru 1A, which tested a Jurassic horst block in the Vulcan Sub-basin, stimulated further exploration in the offshore part of the Bonaparte Basin, and 21 exploration wells were drilled in the next three years (1984 to 1986). Of these wells, 12 were located in the Vulcan Sub-basin and on the western flank of the Londonderry High. This phase of exploration resulted in the discovery of a further three commercial oil accumulations in the Vulcan Sub-basin (Cassini, Challis and Skua). Oil production from the Jabiru Challis and Cassini fields is via Floating Production Storage and Offloading Vessels (FPSOs). Production ceased at Skua in 1997.

During the mid 1980s, two non-commercial discoveries of oil were made in stacked reservoirs within the Early Carboniferous Milligans Formation and Late Carboniferous to Early Permian Kuriyippi Formation at Turtle 1 (1984) and Barnett 1 (1985) in the inshore Petrel Sub-basin.

After a brief downturn in 1987, levels of offshore exploration drilling in the Bonaparte Basin accelerated. Between 1988 and 1990, 31 exploration wells were drilled in the Vulcan Sub-basin. Drilling results from these wells proved disappointing, although several other oil and gas discoveries were made. Further to the north on the Troubadour Terrace, Evans Shoal 1 (1988) identified a significant gas accumulation within the Jurassic Plover Formation, with the appraisal well, Evans Shoal 2, being drilled later in the same year.


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Resolution of the territorial dispute between Indonesia and Australia in 1991 established of the Zone of Cooperation (ZOC) and allowed exploration on the Sahul Platform to resume. Between 1992 and 1998, the focus of exploration in the offshore Bonaparte Basin shifted to this area. Of the 73 exploration wells drilled here during this period, 43 were located either on or adjacent to the Sahul Platform, Laminaria High and Flamingo High. The first commercial petroleum success in the area resulting from this phase of exploration occurred in 1994, with the discovery of oil at Elang 1 and the identification of a new oil play on the Flamingo and Laminaria highs.

In 1999, Timor-Leste was granted independence by Indonesia. This created a climate of uncertainty with regard to petroleum exploration in the Zone of Cooperation. In that year, only one exploration well (Jura 1) was drilled in the former ZOC Area A. Since that time, Coleraine 1 (2000) and Kuda Tasi 1 (2001) have been drilled within ZOC Area A. These wells were followed by oil recoveries at Kuda Tasi 2 (2003) in what is now known as the Joint Petroleum Development Area (JPDA).

Exploration drilling on the Londonderry High in 2000 identified numerous gas accumulations within the Hyland Bay Formation at Prometheus 1, Rubicon 1, Ascalon 1A and Saratoga 1.

In the Petrel Sub-basin, two wells (Sandbar 1 and Blacktip 1) were drilled during 2001 in the inshore portion of the basin. No hydrocarbons were encountered in Sandbar 1, but Blacktip 1 was completed as a gas discovery. This well encountered a 20 m gross gas column within the Triassic Mount Goodwin Formation, and a 339 m gross gas column from several high quality, stacked reservoir zones within the Early Permian Keyling Formation. Further drilling in the Petrel Sub-basin met with limited success, with Shakespeare 1 and Weasel 1 having minor oil and gas indications. Polkadot 1 (2004) encountered non-commercial gas in the Hyland Bay Formation, but the recently drilled well Blacktip North 1 (2006), which also targeted gas in this formation, was dry.

Although drilling continued in the Vulcan Sub-basin throughout 2002–2003, no new commercial discoveries were made. However, from June 2005 to mid-2006, there has been a revival in exploration success with the wildcat wells Katandra 1, 1A and Vesta 1 discovering both oil and gas. The development wells Puffin 7 and 9 recovered oil, and the extension/appraisal wells to the Montara field by Coogee Resources successfully discovered more oil at Swift North 1, ST1 and Swallow 1.
During 2002–2003, drilling on the Laminaria High and Flamingo High has been focussed on the development of the accumulations at Buffalo, Kuda Tasi, Laminaria and Bayu/Undan. Of the few recent exploration wells that have been drilled in this area, Firebird 1 (2005) discovered gas.

Drilling has been active in the Malita and Calder graben area since mid-2005, with gas discoveries been made at Caldita 1 (2005), Evans Shoal South 1 (2006) and Barossa 1, ST1 (2006), with appraisal drilling continuing at Caldita 2 (2007).


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Londonderry High Exploration History

There have been three main periods of drilling exploration in the release areas. The first period began with initial exploration in the 70’s with the drilling of Eider 1 (1972) by Arco. Whimbrel 1 (Arco, 1974) and Tamar 1 (Getty Oil Dev Co, 1979) soon followed, with all three wells primarily targeting the Mesozoic section beneath the Bathurst Island Group regional seal. These wells confirmed the presence of hydrocarbons in the region with the best drilling result being a gas show in Eider 1.

This phase was followed by an intense period of drilling in the mid-80s to early 90s, with a total of 12 wells drilled in the permit areas. Three main companies were operating in the region at this time: Bond Corporation, Western Mining Corporation Ltd and LASMO Oil (Australia Ltd). Again the primary targets of the wells were high quality Mesozoic reservoirs beneath the Bathurst Island Group regional seal. One exception to this is Stork 1, which targeted a Late Cretaceous sand; however, no significant hydrocarbons were intersected. While commercial success was elusive, significant hydrocarbons were intersected during this time. Avocet 1A and 2 contained a number of residual oil columns in Jurassic and Cretaceous units. The lack of commercial success in these wells was attributed to structure breach by Miocene fault re-activation. Halcyon 1 intersected a 17 m gas column hosted within the Flamingo Group, proving that there can be accumulation preservation in the region despite fault movement.

Exploration continued in the late 90s to 2001 with three wells drilled; Kittiwake (Boral, 1998), Wambenger (Newfield, 2000) and Backpacker (Newfield, 2001). These wells contained oil and gas indications with no significant hydrocarbon accumulations.

Excellent seismic coverage is available for the entire Londonderry High area. There has been coverage of 1980s vintage 2D seismic lines with 3 km (average) line spacing and in some areas closer spacing over prospects. Several prospect level 2D seismic studies were undertaken in the 1990s along with more sparsely spaced regional lines. One 3D seismic survey was acquired (WesternGeco, 2003). More sparsely spaced 2D seismic lines, at approximately 10 km spacing for 1980s data and more widely spaced regional 1990s data is available over the southern part of the Londonderry High.


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Relevant wells

A number of wells have been drilled in the release areas. Area W07-1 contains Avocet 1A (1986), 2 (1989), Barita 1 (1986), Cygnet 1 (1986), Drake 1 (1987), Eider 1 (1972), Fulica 1 (1989), Garganey 1 (1989), Halcyon 1 (1991), Jacana 1 (1991), Kittiwake 1 (1998) and Stork 1 (1990). The best drilling result to date has been a gas column intersected by Halcyon 1 and residual oil columns in Avocet 1A and 2. Eider 1 contains gas shows. Oil and gas indications are common within the other wells. Wells either within, or in close proximity to, Area W07-2 include Backpacker 1 (2001), Kite 1 (1998), Saratoga 1 (2000), Tamar 1 (1979) and Wambenger 1 (2000). These wells contain either oil or gas indications (or both). Permit W07-3 contains Crane 1 (1986), Ibis 1 (1986) and Whimbrel 1 (1974). Both Crane 1 and Whimbrel 1 have oil and gas indications. Ascalon 1,1A was drilled just to the east of Area W07-2 and encountered oil and gas shows.

Eider 1 (1972) was drilled by Arco Australia Ltd in permit WA-15-P testing Triassic to Early Cretaceous sedimentary rocks in a northeast–southwest-trending horst block. The well reached a total depth (TD) of 2835 mKB with gas shows recorded while drilling the Bathurst Island Group section. The quality of the Jurassic Plover Formation was confirmed with oil staining observed in sidewall cores. Zones of interest in this section were tested, but all proved to be water-bearing. It is likely the oil is residual from earlier migration.

Halcyon 1 (1991) was drilled by LASMO Oil (Australia) in permit WA-199-P and tested sandstones of the Bathurst Island Group, the Flamingo Group and the Triassic Sahul Group within a fault-dependent structure. The well reached a TD of 2090 mKB, intersecting good quality reservoirs in the targeted horizons. RFT’s confirmed that the well encountered a 17 m gas column in the Flamingo Formation. The well was plugged and abandoned as a minor gas discovery, but it demonstrated that hydrocarbon columns could be preserved despite Miocene fault reactivation. Figure 4 shows part of Geoscience Australia’s regional seismic line 116/09, which transects Area W07-1 and intersects Halcyon 1.


Avocet 1A (1986) was drilled by the Bond Corporation in permit WA-199-P, targeting the Flamingo Group in a horst block. The well reached a TD of 2217 mKB and confirmed the reservoir quality of the target unit. Three residual oil columns were identified; a 21 m residual oil zone in the Bathurst Island Group, an 18 m residual oil column in the Flamingo Group and a 43 m residual oil column in the basal Flamingo Group and underlying Plover Formation. Gas indications were also present throughout the sections. The structure was interpreted to have been breached by post-Miocene reactivation.

Avocet 2 (1989) was drilled as an up-dip follow-up to the Avocet 1A well. The well reached a TD of 2000 mKB, with three residual oil columns intersected; a 22 m residual oil zone in the Bathurst Island Group, a 10 m residual oil column in tight Flamingo Group sandstones and a 59 m residual oil column within the basal Flamingo Group and underlying Plover Formation sandstones. The oil accumulations at this location have also been interpreted as breached by post-Miocene reactivation. Figure 5 shows part of Geoscience Australia’s regional seismic line 116/09, which transects Area W07-1 and intersects Avocet 1A and 2 and shows typical structural style and stratigraphic relationship across the Londonderry High and into the Sahul Syncline.

Kite 1 (1998) was drilled to test the Flamingo Group sandstones in a drape over a Triassic–Jurassic horst. No hydrocarbons were encountered in the primary objective, although some gas indications and excellent visual porosity were observed. Figure 6 shows Geoscience Australia’s regional seismic line 116/07, which transects areas W07-2 and W07-3, and intersects Kite 1 to demonstrate the typical structural style and stratigraphic relationship across the Londonderry High, Sahul Syncline and Malita Graben.

Ascalon 1, 1A (2000) was drilled to evaluate the Permian section on the Londonderry High. The well encountered oil shows in the Lower Cretaceous Sandpiper Sandstone, and a 6.1 m net gas pay in the Permian Hyland Bay Formation. A drill stem test (DST) over the depth ranges 4557–4559 m and 4573–4617 m within the Hyland Bay Formation flowed gas at 29,490 m3/day, with a maximum flow of 70,800 m3/day.

Saratoga 1 (2000) tested an anticline with independent fault closure at the Elang and Plover Formation level. The well encountered a 4.3 m net gas pay within the Late Jurassic Flamingo Group.

To the south of Area W07-2, the two wells Prometheus 1 and Rubicon 1, both drilled in 2000, targeted Permian Hyland Bay Formation sandstones in a fault dependent structure. Prometheus 1 encountered a 72 m gross gas column within the Hyland Bay Formation. Rubicon 1, located 3 km east of Prometheus 1, intersected a 30 m gross gas column in the Hyland Bay Formation. The gas-water contact in Rubicon 1 occurs at the same depth as that in Prometheus 1, and is interpreted to be an extension of the Prometheus discovery, and confirms that the structure is filled to the mapped spill point (King, 2001).

Further to the southeast of Area W07-2, Torrens 1 (1993) targeted fluvio-deltaic sands of the Early Permian Keyling Formation within a fault dependent closure. Residual oil in sandstones of the Permian Fossil Head Formation and possible minor moveable oil and gas in the Tern Member of the Hyland Bay Formation and the Kuriyippi Formation were recorded. Analysis of oil-bearing fluid inclusions (Lisk and Brincat, 1998; Edwards et al, 2000) indicated a 42 m palaeo-oil column within the Fossil Head Formation. Kufpec (1994) attributed the lack of significant hydrocarbons to a lack of structural closure.


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Relevant Wells Listing

Well Operator Year Total Depth (m) Hydrocarbons
Avocet 1 Bond Corporation Pty Ltd 1986 346  
Avocet 1A Bond Corporation Pty Ltd 1986 2217 Potential oil zone, gas indication
Avocet 2 Bond Corporation Pty Ltd 1989 2000 Oil & gas indications
Backpacker 1 Newfield Australia (Ashmore Cartier) Pty Ltd 2001 2276 Oil & gas indications
Barita 1 Bond Corporation Pty. Ltd. 1986 2500 Oil & gas indications
Crane 1 Western Mining Corporation Limited 1986 2855 Oil & gas indications
Cygnet 1 Bond Corporation Pty Ltd 1986 2050 No shows
Drake 1 Bond Corporation Pty Ltd 1987 2380 Oil indication
Eider 1 Arco Australia Limited 1972 2834.64 Gas flowed on test
Fulica 1 Bond Corporation Pty Ltd (Energy Resources Division) 1989 2674 Oil & gas indications
Garganey 1 Bond Corporation Pty Ltd (Energy Resources Division) 1989 1091  
Garganey 1 ST1 Bond Corporation Pty Ltd 1989 2481 Oil & gas indications
Halcyon 1 LASMO Oil (Australia) Limited 1991 966 Potential oil zone, oil indications
Halcyon 1 DW1 LASMO Oil (Australia) Limited 1991 2090  
Ibis 1 Western Mining Corporation Limited 1986 1475 No shows
Jacana 1 Lasmo Oil (Australia) Limited 1991 1718 No shows
Kittiwake 1 Boral Energy Resources Ltd 1998 2606 Oil & gas indications
Kittiwake 1 ST1 Boral Energy Resources Ltd 1998 2800 Oil & gas indications
Stork 1 LASMO Oil (Australia) Limited 1990 1400 No shows
Tamar 1 Getty Oil Development Co Ltd 1979 2863 Oil & gas indications
Wambenger 1 Newfield Australia (Cartier) Pty Ltd 2000 2653 Oil indication
Whimbrel 1 Arco Australia Limited 1974 2058.6 Oil & gas indications

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