Canning Petroleum Permit Applications in Western Australia

Canning Petroleum Pty Ltd submitted three applications to the Department of Mines in 2012 that were granted in 2014.

Onshore Bonaparte Basin

L11-2 Acreage Release   (map)

The L11-2 acreage release is located on the northern edge of the Broome Platform, which is a mid-basin high that separates the Fitzroy Trough from the southern Canning sub-basins. The platform has been a positive feature since the Ordovician when bounding faults began to be active. The Dampier Fault on the north side of the Broome Platform runs through the center of L11-2.

Map of the seismic coverage over the L11-2 Acreage Release (outlined in red) showing the major structural features and the well control that was used in the geological interpretation by Canning Petroleum Pty Ltd.

The structural history of L11-2 is dominated by the Dampier Fault, which was active in the Late Devonian and Early Carboniferous as a down-to-the-north normal fault. The Dampier Fault separates the Broome Platform on the south from the Jurgurra Terrace on the north with up to 1500 meters of displacement at the Ordovician horizons. The Fenton Fault, located to the north of L11-2, separates the Jurgurra Terrace from the Fitzoy Trough to the north. This depth map (in meters) on the top of the Goldwyer Shale shows the structural displacement on the Dampier Fault:

Map of the subsea depth to the top of the Goldwyer Shale in L11-2 (in meters). The Goldwyer Shale is erosionally removed by the Basal Grant Unconformity around the Dampier Downs-1 well in the center of L11-2.

Uplift of the Broome Platform resulted in non-deposition or erosion of the majority of the Siluro-Devonian interval to the south of the Dampier Fault. Some of the Ordovician interval was also removed by erosion to the south of the Dampier Fault over parts of L11-2. As a result, the Permian Grant Formation unconformably overlies the Ordovician Willara Formation around the Dampier Downs-1 well, in the central portion of L11-2, and the Goldwyer Shale has been eroded away. The Goldwyer Shale interval is partially to completely preserved beneath the Basal Grant Unconformity on the Broome Platform in the southeastern portion of L11-2 (at depths of 800 to 1600 meters subsea) and on the Dampier Shelf in the western part of L11-2 (at depths of 2000 to 3400 meters subsea). The entire Ordovician interval is inferred to be present to the north of the Dampier Fault on the Jurgurra Terrace (at depths of 3000 to 4500 meters subsea) in L11-2. The subcrop map on the base of the Grant Formation shows that the Goldwyer Shale is partially eroded away in the central part of L11-2, but is preserved beneath the Ordovician Nita Formation and the Carribuddy Group in the remainder of L11-2. The Carboniferous Fairfield Group is only preserved from erosion beneath the Permian Grant Formation to the north of the Dampier Fault:

Subcrop map on the base of the Grant Formation in L11-2.

L11-5 Acreage Release   (map)

Acreage release L11-5 is located on the Broome Platform. The Admiral Bay Fault on the south side of the Broome Platform runs just to the southwest of L11-5. The Collins Fault occurs to the northeast of L11-5.

Map of the seismic coverage over the L11-5 Acreage Release (outlined in purple) showing the major structural features and the well control that was used in the geological interpretation by Canning Petroleum Pty Ltd.

Uplift of the Broome Platform resulted in non-deposition or erosion of the majority of the Siluro-Devonian and Carboniferous interval between the Admiral Bay Fault and the Collins Fault, but the Goldwyer Shale and Nita Formation are present throughout L11-5. Some of the Ordovician Carribuddy Group was removed by erosion at the base of the Grant unconformity in the northern part of L11-5. In the southernmost portions of L11-5, the Upper Ordovician salt deposits in the Carribuddy Group are preserved beneath the Basal Grant Unconformity. The relationship of the Goldwyer Shale to the overlying salt sections in the Carribuddy Group is shown in this stratigraphic section:

Stratigraphic column for the Canning Basin, showing the relationship of the Middle Ordovician Goldwyer Shale to the overlying Nita Formation and Carribuddy Group on the Broome Platform.

This structure map on the top of the Goldwyer Shale shows the subsea depth to the top of the Goldwyer Shale (base of the Nita Formation) in L11-5:

Map of the subsea depth to the top of the Goldwyer Shale in L11-5 (in meters).

The Goldwyer Shale can be divided into three members on the Broome Platform. The upper member is comprised of grey to dark grey shale with moderate gamma-ray activity. The middle member is predominately pale grey limestone with interbeds of dark grey shale with low average gamma-ray activity. The lower member is predominately a dark grey to black shale and siltstone interval with some fine-grained sandstone in the lower portion and has moderate to high gamma-ray activity. The lower member can be divided into two units to distinguish the basal siltstone from the overlying black shale. The basal siltstone often has the best gas shows:

Composite log over the middle and lower Goldwyer Shale in the Aquila-1 well illustrating the oil and gas shows in the black shale and siltstone intervals of the lower member.

The Goldwyer Shale is Middle Ordovician in age and is up to 600-m thick in L11-5. It has been shown to be a good source rock in the wells on the Broome Platform and Barbwire Terrace to the north and east of L11-5. Rock-Eval pyrolysis data from composite cuttings samples from the Aquila-1 to the northwest of L11-5 show that the lower Goldwyer Shale has an average TOC content of 1.5% and TOC values of up to 3.2% in sidewall core samples. The TOC content of whole cores taken in the Goldwyer Shale in the McLarty-1 range up to 4.7%, which is the highest TOC reading that has been observed in the Goldwyer Shale in the vicinity of L11-5, although there is some question as to the reliability of these readings because an oil-based mud was used to drill the McLarty-1:

Regional seismic lines through L11-5 suggest that the southwestern portion of L11-5 may have occupied a shallow marine area of the Middle Ordovician seaway when the Goldwyer Shale was being deposited. This inference is supported by the observation of bioherms in the Nita Formation and Goldwyer Shale along the Admiral Bay Fault, which would have been deposited in shallow water, in contrast to the deeper water depositional environments inferred for these intervals in wells further to the northeast. The isopach of the upper Goldwyer Shale in L11-5 suggests the basin floor sloped northeastward away the Admiral Bay Fault Zone during the Middle Ordovician before the basin shoaled to shallow water depths during deposition of the overlying Nita Formation:

Canning Petroleum’s interpretation of the upper Goldwyer Shale isopach thickness in Acreage Release L11-5.

The seismic lines through L11-5 illustrate that normal faults were active during deposition of the lower Goldwyer Shale, resulting in low-relief horst and graben features. The extensional tectonic activity during deposition of the lower Goldwyer Shale created small depocenters where the lower Goldwyer Shale is thicker:

Canning Petroleum’s interpretation of the lower Goldwyer Shale isopach thickness in Acreage Release L11-5.

The thermal maturation studies indicate that the Goldwyer Shale is in the oil generation window on the Broome Platform where it occurs at subsea depths of 800 to 1500 m, with peak oil generation occurring at a subsea depth of about 1200 m. The wet gas window is inferred to occur at burial depths of greater than 1500 meters. The lower Goldwyer Shale occurs at subsea depths of 1000 to 1200 meters in the northern part of L11-5, so the formation is expected to be oil prone with some associated gas in that part of the acreage release. In the central and western parts of L11-5 the base of the lower Goldwyer Shale is at subsea depths of 1200 to 1500 meters, where it would be expected to produce light oil with associated gas and condensate. In southeastern L11-5 the base of the Goldwyer Shale is buried to as deep as 2000 meters were it may only produce wet gas:

Map of the subsea depth to the base of the Goldwyer Shale (top of the Willara Formation) in Acreage Release L11-5 (in meters).