Areas W07-12 to W07-15
Canning Basin
Exploration History
Until the mid-1980s, exploration largely focussed on the onshore northern and central basin areas and targeted reefs within the Devonian section and overlying Permo–Carboniferous clastics. During the 1980s an extensive phase of petroleum exploration resulted in the acquisition of many thousands of kilometres of seismic data and the drilling of many additional wells, but this yielded little commercial success (Kennard et al, 1994). Production is limited to six small oil fields on or adjacent to the Lennard Shelf (Blina, Boundary, Lloyd, Sundown, West Kora and West Terrace), and development of the Point Torment gas field (also on the Lennard Shelf) is being considered to generate power for the West Kimberley region. The largest accumulation, Blina (approximately 2 MMbbls), is reservoired within dolomites of the Late Devonian Nullara Limestone carbonate bank and (to a lesser extent) within the Early Carboniferous Yellow Drum Formation. All other accumulations are within clastics of the Early Carboniferous Anderson Formation (Lloyd, Point Torment and West Kora) and Late Carboniferous Grant Group (Boundary, Sundown and West Terrace).
The small size of the discoveries made in the Devonian reef complexes and overlying Permo–Carboniferous clastics in the onshore northern and central basin areas, and the low oil price in the late 1980s meant that exploration languished (Black, 2006). Since that time, the Canning Basin has seen a low level of systematic exploration and, to date, there are only approximately 250 wells drilled onshore, which is low for a basin of this size. The basin is substantially under-explored with few valid structural tests.
A total of 15 wells have been drilled offshore from the Canning Basin, with the majority sited in the Mesozoic depocentres of the Rowley and Bedout sub-basins; none with commercial success. Six wells were drilled in the Offshore Canning Basin between 1970 and 1984, with the only significant hydrocarbon shows being recorded in Perindi 1.
Lacepede 1 and 1A were drilled in 1970, approximately 129 km northwest of Broome in the central Oobagooma Sub-basin. Lacepede 1 was abandoned at 224 m due to technical difficulties and Lacepede 1A reached a total depth (TD) of 2286 m. The wells were drilled to test an elongate east–west-trending anticlinal structure. Lacepede 1A penetrated Miocene sediments unconformably overlying an Early Cretaceous to Late Carboniferous (originally interpreted to be Late Permian; Helby and Partridge, 1982) sedimentary section. Lacepede 1A penetrated the most complete Jurassic section in the Canning Basin at that time, with rocks of Early Jurassic age being recorded for the first time. The entire Triassic and most of the Permian section is absent, such that Jurassic (Tithonian–Toarcian) sediments unconformably overlie Early Permian (Asselian) to Late Carboniferous sediments. No significant hydrocarbons shows were encountered in the wells. Slight increases in the background gas readings occurred in the Jurassic and Permian sections. However, no fluorescence was observed and wireline logs indicated 100 % water saturation throughout the well. The wells confirmed the presence of thick, porous and permeable reservoirs in the Early Cretaceous and Jurassic sections and are thought to have adequately tested the Cretaceous, Jurassic and uppermost Permian sections of the Lacepede structure.
Wamac 1 was drilled in 1973 to a TD of 2764 m and is located 110 km northwest of Broome. The well was drilled as a test of the sedimentary section in the Wamac structural feature. This is a seismically mapped positive feature of Palaeozoic age with an east–west elongation and an areal closure of >250 km2 in the ?intra-Devonian and also possible closure in the ?Early Permian. The structure was found to be a partly fault-controlled positive feature over a basement rise, with high interval velocities below the structure potentially due to a reefal section, or an igneous intrusion. Wamac 1 penetrated a sedimentary section ranging from Quaternary to Carboniferous age, being of similar character to that in Lacepede 1A. The Palaeozoic sediments are intruded by dolerite of Permian to Early Triassic age. It was programmed for 3659 m, but was terminated in a dolerite sill because of drilling problems associated with the collapse of fragments and blocks into the well. No hydrocarbon shows were recorded in clastic rocks, due mostly to lack of closed structure in the Mesozoic, and possibly also in the Late Palaeozoic. Slight increases in methane were observed at multiple levels and fluorescence was observed at 1830 m. Low porosity and negligible permeability (due to induration of sandstones by intrusions) may have been responsible for the lack of hydrocarbon indications throughout the Palaeozoic.
Kambara 1 was drilled in 1982, 136 km north of Broome on the Pender Terrace. The well was programmed to 3175 m to test an interpreted Devonian pinnacle reef, but terminated at 3150 m after passing through 700 m of tight platform limestones and 350 m of interbedded sandstones and limestones. No recognisable reef facies were encountered in the well; instead a sequence of Late Devonian platform limestones were penetrated, overlying interbedded basinal limestones and sandstones. The target reef was reinterpreted to be diffractions within a flat limestone platform, the result of erosional topography on the platform surface, or a pinnacle reef with a well developed lagoonal facies in the centre. The well intersected relatively thin Cretaceous (350 m) and Jurassic (~250 m) sections and relatively thick Permian (~550 m), Carboniferous (~850 m) and Devonian (>1 km) sections. In this respect, it is similar to the Onshore Canning Basin succession rather than the earlier wells drilled in the Oobagooma Sub-basin. The well intersected porous and permeable sandstones and good seal lithologies in the Permo–Carboniferous section. The Devonian sandstones and limestones lacked significant porosity. The sequence drilled was immature down to and including most of the Devonian section (~2650 m). The only good source material in the Permo–Carboniferous was immature. Kambara 1 reached a total depth without encountering any hydrocarbon shows. The lack of hydrocarbon shows probably indicated that there was no mature source adjacent to, or overlaying the limestone section. Also lack of significant porosity in the Devonian section and lack of sealing lithology over the limestone section probably precluded the occurrence of significant hydrocarbons.
Perindi 1 was drilled in 1983, 126 km north of Broome on the Pender Terrace. The well was programmed to 1921 m, primarily to test multiple sandstone horizons within the Poole Sandstone, Grant Group and Anderson Formation, in a domal structure formed by the emplacement of igneous intrusions. The secondary objective in the well was the underlying Devonian Pillara Formation limestones on the southern flank of the Tappers Inlet High. The well was terminated at 1867 m due to partial lost circulation in the Pillara Formation carbonates and lack of encouraging hydrocarbon shows. The Cretaceous and Jurassic sections are somewhat thicker than in the nearby Kambara 1 well, with a much thicker Permian section, but much thinner Carboniferous section. The Jurassic, Cretaceous and Permian (Grant Group) all contain porous and permeable sandstones. The Devonian carbonates (Pillara Formation) exhibit excellent porosity and permeability, which may be due to karst formation during fault block exposure. The presence of (the thin) Laurel Formation indicates that this unit occurs higher than anticipated on structural highs, and the lack of sandstone in the Poole Sandstone suggests it may have good seal quality in this offshore facies (also observed in Kambara 1). Eight zones with hydrocarbon shows were encountered in Perindi 1 within the Poole Sandstone, Grant Group, and Laurel and Pillara formations. Oil staining, cut and fluorescence occurred within the limestone units of the Poole Sandstone. Minor oil shows were recorded in sandstones at the top of the Grant Group, and in three zones below the dolerite intrusive body. The well penetrated 6 m of Laurel Formation siltstones and tight sandstones with observed oil staining, cut and fluorescence, before passing into limestones and dolomites of the Pillara Formation. Bitumen and minor gas shows were apparent within these carbonates, which show decreasing porosity with depth.
Thermal alteration index and vitrinite reflectance studies suggest that the top of maturity is anomalously high (828 m) compared to nearby wells (1750 m in Tappers Inlet 1, 34.5 km to the east). This elevated maturity is believed to be the direct result of heating during the emplacement of the intrusive dolerite cone sheet that surrounds the Perindi structure, which is penetrated between 1379 and 1535 m in Perindi 1. Preliminary biomarker analyses have shown that the Perindi 1 oil stains (Geoscience Australia unpublished data) are most similar to the Canning Basin oils at Lloyd, Sundown and West Terrace, as well as the Barnett and Turtle oils in the Petrel Sub-basin, Bonaparte Basin (AGSO and GeoMark, 1996; Edwards et al, 1997). The Barnett and Turtle oils have been typed to the Early Carboniferous (early–middle Tournaisian) Langfield Group by Gorter et al (2004). Therefore, by analogy, these data imply that the most likely source of hydrocarbons below the intrusion is the Early Carboniferous Laurel Formation (Fairfield Group, and time equivalent to the Langfield Group) located off-structure, rather than the underlying Ordovician sediments. The lack of oil shows beneath seals in the Grant Group above the intrusion suggests that migration of oil was from directly beneath the structure and that the cone sheet acted as a barrier to vertical migration. The shows at the top of the Grant Group and within the Poole Sandstone also appear to be sourced from the Laurel Formation with migration potentially occurring around the intrusive body. The lack of a significant oil accumulation may indicate charge limitations or the presence of leaking faults on the crest of the structure. Potentially, migrating hydrocarbon could be trapped off-structure between the doleritic cone sheet and seal lithologies within the Grant Group.
Pearl 1 was drilled in 1983, 25 km west-northwest of Broome on the Jurgurra Terrace. It was the first wildcat to be drilled within this area. It was drilled on a modest anticlinal closure mapped at the pre-Grant unconformity and two deeper levels (both of which were determined to be intrusive units). The primary objective was the Tandalgoo Formation with the secondary objective sandstones of the Grant Group. It encountered a Mesozoic section similar to that onshore and in Lacepede 1A and Wamac 1 (although no Triassic). The Carboniferous section is very thick (>1 km) being mostly lower Grant Group with porous sandstones between siltstone/shale sealing units offering good reservoir potential. Pearl 1 was plugged and abandoned after encountering no hydrocarbons. Log interpretation indicates the entire section to be water saturated. No formation testing or coring was conducted. Dolerite was encountered at 2144 m and after penetrating 59 m of such drilling was terminated. The primary objective (Tandalgoo Formation) was not reached. The operator concludes that dolerite intrusives occur in succession in the Early Carboniferous. Country rock is indurated and overmature for hydrocarbon generation. Early Carboniferous shales; above the intrusives are indicated to be good oil and gas source rocks and are mature for hydrocarbon generation. Porous sandstones of the Grant Group between siltstone/shale sealing units offer good reservoir potential.
Minjin 1 was drilled in 1984, 130 km north of Broome on the Pender Terrace. The well was programmed to 1940 m in a closed domal structure of early Permian age which was believed to have been formed by the emplacement of igneous intrusions. The primary objective was sandstones within the Permo- Carboniferous Grant Group and the secondary objective was the Devonian Pillara Formation limestones, which contained excellent porosities in Perindi 1. The well penetrated a Cretaceous to Devonian section and an 85 m thick doleritic intrusion was intersected within the Grant Group. The overall succession was similar to Perindi 1 although the Carboniferous was entirely absent. Porous and permeable sandstones were encountered throughout the Jurassic and Cretaceous sequences and within the Grant Group. The Pillara Formation contained no intragranular, vuggy or fracture porosity and is considered tight. The well terminated at 1850 m after drilling through 301 m of these tight limestones. There were no hydrocarbon shows encountered during drilling mainly due to lack of source beds. From vitrinite reflectance readings it is surmised that increased maturity levels are probably a result of the igneous intrusion superheating the formation fluids contained in the sediment during its emplacement.
There has been very little exploration in the Offshore Canning Basin since the mid-1980s, with no permits awarded since that time. Regional spec seismic was acquired across the basin in 1988, and this grid later was tied to the wider North West Shelf regional grid by an AGSO (now Geoscience Australia) seismic survey.
More recent exploration has been undertaken to the west in the Rowley Sub-basin, with the drilling of two unsuccessful deep-water wells; Whitetail 1 (Woodside, 2003) and Huntsman 1 (Woodside, 2006).
Geoscience Australia conducted a hydrocarbon seepage survey of the Offshore Canning Basin and Rowley Sub-basin in June 2006 (Survey SS06/06). Active fluid escape pockmarks and fluid vents were identified on side-scan sonar and seabed video footage near the junction of the Oobagooma Sub-basin and Broome Platform (within Area W07-14), but petrographic and geochemical analysis of sediments recovered from the pockmarks suggest that the fluids are of normal marine composition and show no evidence of thermogenic hydrocarbons (Kennard, 2007). Preliminary results of this seepage survey are available at: http://www.marine.csiro.au/nationalfacility/voyagedocs/2006/index.htm.
Relevant Wells Listing
| Well | Operator | Year | Total Depth (m) | Hydrocarbons |
|---|---|---|---|---|
| Barlee 1 | WAPET | 1960 | 2469 | No shows |
| Bedout 1 | B.O.C. of Australia Ltd | 1971 | 3073 | |
| Cow Bore 1 | Aust Gulf Oil Co | 1983 | 2940 | Oil & gas indications |
| Crab Creek 1 | Bridge Oil Ltd | 1987 | 1778 | Oil indication |
| Curringa 1 | Esso Explor and Prod Aust Ltd | 1982 | 2335 | |
| East Crab Creek 1 | Aust Gulf Oil Co | 1984 | 2813 | |
| East Mermaid 1 | Shell Development (Australia) Pty Ltd | 1973 | 4067.6 | |
| Freney 1 | Ampol Explor Ltd | 1988 | 1115 | |
| Kambara 1 | Esso Exploration and Production Australia Inc | 1982 | 3150 | No shows |
| Lacepede 1 | B.O.C. of Australia Limited | 1970 | 224 | |
| Lacepede 1A | B.O.C. of Australia Limited | 1970 | 2286 | No shows |
| Lagrange 1 | BP Petroleum Development Australia Pty Ltd | 1983 | 3260 | No shows |
| Minjin 1 | Esso Exploration and Production Australia Inc. | 1984 | 1850 | Gas indications |
| Moogana 1 | Esso Australia Limited | 1980 | 2213 | Oil indication |
| Pearl 1 (Home Energy) | Home Energy Company Ltd. | 1983 | 2203 | Gas indications |
| Pender 1 | WAPET | 1972 | 912 | |
| Perindi 1 | Esso Exploration and Production Australia Inc. | 1983 | 1867 | Oil recovered, gas indication |
| Tappers Inlet 1 | WAPET | 1971 | 2856 | Oil indication |
| Wamac 1 | Amax Petroleum (Australia) Inc. | 1973 | 2764 | No shows |
| Yulleroo 1 | Gewerkschaft Elwerath | 1967 | 4572 | Proven gas zone, oil indications |