Areas V07-1, V07-2 and V07-3
Gippsland Basin
Exploration History
The history of oil production in the Gippsland Basin dates back to 1924, when Lake Bunga 1, a water well, was spudded near the township of Lakes Entrance. The well encountered a 13 m oil column in glauconitic conglomerates (Top-Latrobe Group). Over 60 follow-up wells were drilled and by 1941 the field had produced more than 8,000 barrels of heavy oil (~16º API). The most productive well was the Lake Entrance Oil Shaft, which alone produced 5,000 barrels (Beddoes, 1972; Boutakoff, 1964).
Extensive exploration in the Gippsland Basin did not commence until the mid-1960s. After seismic data had successfully imaged the Central Deep and identified several anticlinal closures, the first successful well, East Gippsland Shelf 1 (later known as Barracouta 1), was drilled by Esso in 1964–65. The well discovered a 102.5 m gas column at a depth of 1,060 m. Following the subsequent discovery of the large Marlin gas field, the Gippsland Basin was initially perceived as a significant gas province. However, in 1967 Kingfish 1 was drilled and encountered the largest Australian oil field known to date, thereby cementing the Gippsland Basin’s place as a prolific, world class oil and gas province.
By the end of 1969, eleven fields had been discovered and the first five (Barracouta, Marlin, Snapper, Kingfish and Halibut) were on production. After the initial phase of very high success rates, the new discoveries, made by the Esso/BHP Petroleum joint venture, were limited through the early 1970s: Cobia 1 (1972), Sunfish 1 (1974) and Hapuku 1 (1975) were discovered, but only Cobia entered production. In 1978, following the implementation of Import Parity Pricing (ie, the removal of government pricing controls on locally produced crude oil, which discouraged exploration), the giant Fortescue oil field was discovered, followed by Seahorse and West Halibut.
Additional players, including Aquitaine, Shell and Phillips, commenced exploration in 1980. Shell, which had previously discovered the Sole gas field in 1973, mapped the Basker/Manta structures and drilled two successful wells, Basker 1 and Manta 1. Non-commercial discoveries were made by Hudbay Oil at West Seahorse, Baleen and Sperm Whale. West Tuna, drilled in 1984, is the last of the large to giant oil discoveries made by the Esso/BHP Petroleum joint venture. This discovery was a rather unconventional one at the time, because the oil was trapped by fault-sealing mechanisms rather than being a simple, large anticlinal closure. In 1986, the joint venture discovered the Kipper gas field, a significant find because a 213 m gas column was intersected in fluvial sandstones of the Golden Beach Subgroup. Another drilling campaign in 1989–90, led to the discovery of the Blackback oil and gas field on the shelf edge, in water depths greater than 400 m. Of special significance is the Archer/Anemone discovery in the southern part of the basin, made by Petrofina in 1989–90. Although the encountered quantities of oil and gas were non-commercial, it was confirmed that hydrocarbon accumulations exist in older Latrobe Group (Golden Beach Subgroup) sediments.
Further exploration wells were drilled in the 1990s, although no new discoveries were made. The main operators Esso/BHP Petroleum concentrated on development and workover drilling to optimise production from the existing fields. Following the privatisation of the State Government owned gas utility companies between 1995 and 1999, a restructured gas market emerged that made it more attractive for explorers to search for gas. This, together with a sustained recovery in the oil price, resulted in a resurgence in exploration activity.
In the last five years, a number of new companies were granted exploration licences in the basin and have committed to extensive work programs. Apache Energy was awarded VIC/P58 and VIC/P59 in the western offshore area and shares interest with Nexus Energy in VIC/P54. As part of their current work program, Apache is scheduled to drill several wells on the southern basin margin in early 2007.
Nexus, one of the latest newcomers to the province, currently operates VIC/P49 and VIC/P56, both of which lie in the eastern, partly deeper water area of the basin. In August 2006, the company sole-risked the exploration well Longtom 3 in VIC/P54 and confirmed additional exploitable reserves in the Longtom gas field.
Bass Strait Oil has expanded its presence exploring in permits VIC/P-41 and VIC/P-47 on the northern basin margin, and in VIC/P-42, southward from the Bream and Kingfish fields. The company drilled two wells: Moby 1 discovered gas east of Patricia/Baleen, whereas Zane Grey 1, drilled west of Kingfish, encountered oil and condensate, but was deemed non-commercial. The company is currently pursuing several promising structures along the eastern part of the Rosedale Fault System.
On a basin-wide scale, Esso/BHP Billiton completed two major 3D seismic surveys, including the 4,060 km2 3D Northern Fields survey, which was acquired between October 2001 and July 2002. This was followed by the 1,000 km2 Tuskfish survey over the Blackback-Terakihi area and extended southwards into the current VIC/P59 permit. The main purpose of these regional 3D-surveys was to establish the remaining oil potential in the deeper Latrobe Group, which is the main driver for renewed exploration investment.
To date, a total of 3.8 Billion stock tank barrels of oil and 6.5 TCF of gas have been produced from the developed fields in the Gippsland Basin (Figure 3), which accounts for 90% of the initial oil reserves and 59% of the initial gas reserves. An additional 153 MMbbls of oil and 1.7 TCF gas are recoverable from undeveloped Esso/BHP Petroleum fields, such as Wirrah, Seahorse and Sweetlips, while further reserves remain in the non-Esso/BHP Petroleum owned license areas, including Kipper, Basker/Manta/Gummy, Patricia/Baleen and Golden Beach. Of these, the Basker-Manta oil development by Anzon commenced production via an FPSO facility in November 2005, while the other gas fields are expected to commence production in the near future.
Despite its long history of extensive exploration, many parts of the basin, especially the southern and eastern regions, are still relatively poorly understood. In the context of seemingly sustained high oil prices, the Gippsland Basin continues to attract local and international explorers.
Previous exploration in release areas V07-1 to V07-3
Seismic coverage
Seismic data of various vintages cover the 2007 release areas (Figure 11). Much of the recent seismic data from the region was acquired by Bass Strait Oil Ltd in the context of evaluating permit area VIC/P41; this included 223 km of 2D data as infill and 575 km2 of 3D data southward of the Rosedale Fault System in the general area of Sole. This latter survey led to the identification of the Kipling lead, which has a prospective resource of 118 MMbbls recoverable and 820 BCF of gas (Reid, 2005).
Older data includes some of the regional lines acquired by BMR (now Geoscience Australia) in 1987 and the Shell seismic survey GS70A, much of which covers Area V07-2 in a widely spaced grid (Figure 11). Shell also reprocessed the data from the older surveys, which ultimately led to the drilling of Hammerhead 1 and Shark 1. Only sparse seismic data are available for the northernmost part of Area V07-1 and the southern portion of Area V07-3.
Well control
Only one well, Northright 1, has been drilled within the three 2007 release areas in the Gippsland Basin, and this is located in Area V07-1 (Figures 1 and 5). The well was drilled by Eagle Bay Resources in 2001, and unsuccessfully targeted a Latrobe-pinch-out play on the basin’s Northern Platform. Northright 1 penetrated 27 m of Latrobe Group sediments (Kingfish Formation) and reached total depth (TD) at 391 mKB within the Strzelecki Group. Although the Latrobe section included a valid reservoir unit, the well was dry, probably because of inadequate sealing facies, though it may be that the well was either in a migration shadow or perhaps located too far from the Central Deep.
Several other wells drilled westward and southward of the three release areas can be used for geological correlations and to gain some understanding of the petroleum systems that operate in the northeastern part of the basin. In 1973, Shell drilled the exploration well Sole 1 and discovered a dry gas field that is estimated to exceed 250 BCF of GIIP. The reservoir unit is represented by marine sandstones near the top of the Latrobe Group. The overall Latrobe section is 213 m thick and is predominantly marine; it includes a 10 m thick Kate Shale unit, below which a thin section of coal-bearing, lower coastal plain sediments is developed. The follow-up well Dart 1, drilled by Esso in late 1973, intersected a similar facies succession and targeted a separate culmination that proved not to be a valid closure.
Hammerhead 1, drilled in 1982 by Shell, tested an interpreted fault-truncated intra-Latrobe rollover against the Rosedale Fault (Shell Development, 1982). The primary objective, a lower L. balmei (Paleocene) shoreface sandstone (1,432 mKB in the well), was water wet. Hammerhead 1 reached TD in a shale-dominated sequence, believed to be part of the Golden Beach Subgroup. Seismic mapping was not carried out at the T. lilliei level to determine if closure existed. A palynological review some time later indicated that the mudstones are actually Turonian in age (P. mawsonii biozone) and therefore correspond to the Kipper Shale (Partridge, 1999).
Shark 1 (1989) was the last well drilled by Shell in former permit VIC/P22, following a string of discoveries in this fault-controlled part of the basin, ie Basker 1 (1983), Manta 1 (1984) and Kipper 1 (1986). The well tested a down-faulted Golden Beach section; however, the play relied on a cross-fault sealing, shaly Golden Beach section. The lack of hydrocarbons in Shark 1 may be due to missing sealing facies across the major fault, in particular the missing Campanian Volcanics (Figure 4) that are prominently developed in Kipper and the Basker/Manta area.
Relevant Wells Listing
| Well | Operator | Year | Total Depth (m) | Hydrocarbons |
|---|---|---|---|---|
| Admiral 1 | Esso Australia Resources Limited | 1989 | 2162 | Oil & gas indications |
| Basker 1 | Shell Development (Australia) Pty Ltd | 1983 | 3991 | Proven oil & gas zones |
| Basker 2 | Anzon Australia Limited | 2005 | 3414 | |
| Bignose 1 | Shell Development (Australia) Pty Ltd | 1983 | 3995 | Proven gas zone, oil indications |
| Blackback 1 | Esso Exploration and Production Australia Inc. | 1989 | 3400 | Proven oil zone |
| Blackback 1 ST1 | Esso Exploration and Production Australia Inc. | 1989 | 3047 | Oil & gas indications |
| Blackback 1 ST2 | Esso Exploration and Production Australia Inc. | 1989 | 4401 | Oil & gas indications |
| Blackback 2 | Esso Australia Resources Ltd. | 1992 | 3160 | Proven oil & gas zones |
| Blackback 3 | Esso Australia Resources Ltd. | 1994 | 3125 | Oil indication |
| Culverin 1 | Nexus Energy Services Pty Ltd | 2006 | 3758 | |
| Dart 1 | Esso Exploration and Production Australia Inc. | 1973 | 1219 | |
| Great White 1 | Esso Aust Resources Ltd | 1997 | 3472 | Gas indications |
| Grunter 1 | Esso Exploration and Production Australia Inc. | 1984 | 3809 | Proven oil & gas zones |
| Gummy 1 | The Shell Company of Australia Limited | 1990 | 3563 | Potential oil zone, oil indications |
| Hammerhead 1 | Shell Development (Australia) Pty Ltd | 1982 | 2130 | Oil & gas indications |
| Hapuku 1 | Esso Exploration and Production Austraila Inc. | 1975 | 3649.7 | Proven oil & gas zones |
| Judith 1 | The Shell Company of Australia Limited | 1989 | 2958 | Oil & gas indications |
| Leatherjacket 1 | Esso Exploration and Production Aust. Inc. | 1986 | 951 | Proven oil & gas zones |
| Maclean 1 | Bass Strait Oil Company Pty Ltd | 2005 | 766 | |
| Manta 1 | Shell Development (Australia) Pty. Ltd. | 1984 | 3572 | Proven oil & gas zones |
| Manta 2 | Anzon Australia Limited | 2006 | 971 | |
| Northright 1 | Eagle Bay Resources NL | 2001 | 391 | |
| Scallop 1 | Esso Australia Resources Pty Ltd. | 2003 | 3174 | Potential oil & gas zones |
| Shark 1 | Shell Company of Australia Ltd | 1989 | 3518 | |
| Sole 1 | Shell Development (Australia) Pty. Ltd. | 1973 | 1128.7 | Oil & gas indications |
| Sole 2 | Basin Oil Pty. Ltd. | 2002 | 1005 | Proven gas zone, oil indications |
| Stonefish 1 | Esso Australia Ltd. | 1973 | 3183.6 | Oil recovered, gas indication |
| Sweep 1 | Esso Exploration and Production Australia Inc. | 1978 | 900 | |
| Terakihi 1 | Esso Australia Resources Ltd | 1990 | 3040 | Proven oil zone |
| Volador 1 | Shell Development (Australia) Pty Ltd | 1983 | 1417 | |
| Volador 1 ST1 | Shell Dev (Aust) P/L | 1983 | 4611 | Proven oil & gas zones |
| Wahoo 1 | Esso Exploration and Production Australia Inc | 1969 | 745.5 | |
| Whale 1 | Hudbay Oil (Australia) Ltd | 1981 | 810 | Strong oil indication |
| Whaleshark 1 | Esso Australia Resources Ltd | 1992 | 2870 |