Undiscovered Oil and Gas in Australia's Canning Basin: USGS Assessment

Figure 1. The Canning Basin Province and its six continuous (unconventional) assessment units. Base map from the National Park Service; USGS.

The estimate

Using a geology-based method, the U.S. Geological Survey estimates undiscovered, technically recoverable mean resources in the Canning Basin Province of Australia of:

• 1,275 million barrels of oil (MMBO) — 1.3 billion barrels — with an F95–F5 range of 0 to 4,819 MMBO;
• 34,449 billion cubic feet of gas (BCFG) — 34.4 trillion cubic feet — range 3,903 to 96,210 BCFG;
• 796 million barrels of natural gas liquids (MMBNGL), range 88 to 2,257 MMBNGL.

Most is continuous (unconventional): about 72 percent of the oil (919 MMBO) and 91 percent of the gas (31,270 BCFG). Of that continuous gas, about 47 percent (14,741 BCFG) is potential tight gas.

F95 means a 95-percent chance of at least that amount; F5, a 5-percent chance.

How the basin formed

The Canning Basin is a mosaic of horsts and grabens, first formed by stretching in the Early Ordovician to Silurian. Its faults moved again and again through the Paleozoic and Mesozoic, as squeezing and stretching alternated.

• Source rocks: early stretching and subsidence laid down the marine Goldwyer Formation, the province's most viable source rock. Later stretching in the Late Devonian and early Carboniferous laid down the marine Laurel Formation.
• Squeezing came in the late Silurian to Early Devonian, the middle Carboniferous and the Triassic.
• The big uncertainty: the source rocks are thought to have generated oil and gas before the Triassic uplift and erosion — which may have breached many traps, letting oil and gas escape from conventional fields and from self-sourced reservoirs such as shales. That possible loss is the main geologic uncertainty in the assessment.

Three petroleum systems

• Carboniferous–Permian (in the Fitzroy Trough): gas mainly from marine shales of the Laurel Formation (and possibly the Goldwyer), which moved only locally and was trapped in low-permeability sandstones and siltstones of the Laurel, Yellow Drum Sandstone, Anderson and Reeves formations — the tight-gas unit.
• Goldwyer: oil or gas kept inside the Goldwyer shales after the Triassic uplift — five shale oil and shale gas units, in the Fitzroy Trough (with the Gregory Subbasin), the Broome Platform (Jurgurra and Barbwire terraces, with the Willara Subbasin) and the Kidson Subbasin.
• Paleozoic Composite: oil and gas from several sources in conventional fields that survived the Triassic squeeze — three units, Fitzroy-Lennard, Broome-Jurgurra and Kidson Subbasin.

For the continuous units, well drainage areas, success ratios and ultimate recoveries were guided by U.S. analogs.

Figure 2. The three conventional assessment units. USGS.

Results by assessment unit

Fully risked means; "Prob." is the assessment unit's probability.

More results are on the USGS Energy Resources Program website.

Sources

Based on Assessment of Undiscovered Oil and Gas Resources in the Canning Basin Province, Australia, 2017, USGS Fact Sheet 2018–3023 (May 2018), by the Canning Basin Province Assessment Team, U.S. Geological Survey; a work of the United States government in the public domain. Maps and the results table are taken from the fact sheet's PDF.