Using a geology-based assessment methodology, the U.S. Geological Survey estimated means of 

4.7 billion barrels of undiscovered oil and 227 trillion cubic feet of undiscovered natural gas in three major offshore 

petroleum basins of northwest Australia and in the Gippsland Basin of southeast Australia.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3025

March 2012

World Petroleum Resources Project

Assessment of Undiscovered Conventional Oil and Gas Resources 

of Bonaparte Basin, Browse Basin, Northwest Shelf, and Gippsland 

Basin Provinces, Australia, 2011

Introduction

The U.S. Geological Survey (USGS) assessed the potential for 

undiscovered conventional oil and gas fields within Australia’s major 

offshore petroleum-bearing geologic provinces as part of the USGS 

World Petroleum Resources Project (fig. 1). Four geologic provinces 

as defined by the USGS were assessed in this study. Of these, three are 

mostly offshore of northwest Australia and include the Bonaparte Basin 

Province, Browse Basin Province, and the Northwest Shelf Province. 

The Northwest Shelf Province encompasses the northern offshore portions of the Carnarvon and Canning Basins. The fourth geologic province, the Gippsland Basin Province on the southeast coast of Australia, 

includes resources both onshore and offshore. Many of the basins 

and sub-basins within these provinces originated with basinal extension followed by a post-rift thermal subsidence phase that produced 

carbonate-platform deposits or prograding clastic wedges typical of 

passive margins. Additionally, single or multiple compressional events 

occurred during their complex tectonic histories, which resulted in 

constructive or destructive trap formation.

The methodology for the assessment included a detailed geologic 

framework description for each province based on published literature 

and the definition of total petroleum systems (TPSs) and assessment 

units (AUs). Exploration and discovery history was a critical part of 

the methodology used to estimate sizes and numbers of undiscovered 

accumulations. Each assessment unit was assessed for undiscovered 

oil and nonassociated gas accumulations. Coproduct ratios were used 

to calculate the volumes of associated gas (gas in oil fields) and natural 

gas liquids.

In the Bonaparte Basin Province, a Paleozoic-Mesozoic Composite TPS was defined on the basis of where petroleum source and 

reservoir rocks reflect the complex and progressive tectonic and 

depositional evolution of the region. Four AUs were defined within the 

various sub-basins or sub-basin complexes of the province on the basis 

of varying tectonic history, primary source rock, trap formation, and 

reservoirs. The four AUs are (1) the South Petrel Sub-Basin AU, (2) the 

Londonderry High-North Petrel AU, (3) the Vulcan Sub-Basin AU, and 

(4) the Malita Graben-Sahul Platform AU.

Gippsland CretaceousTertiary Composite TPS

Bonaparte PaleozoicMesozoic Composite TPS

Browse

Paleozoic-Mesozoic

Composite TPS

Northern Carnarvon-Canning 

Mesozoic TPS

Fault-Structured Sandstone 

Reservoirs AU

Latrobe Group Clastics AU

Vulcan Sub-Basin AU

Shelf and Basin

Sandstone AU South Petrel 

Sub-Basin AU

Londonderry High-North Petrel AU

Malita Graben-Sahul Platform AU

 NORTHERN 

TERRITORY

SOUTH AUSTRALIA

WESTERN AUSTRALIA

NEW SOUTH WALES

VICTORIA

QUEENSLAND

TASMANIA

AUSTRALIA

INDONESIA PAPUA NEW GUINEA

100°E 110°E 120°E 130°E 140°E 150°E 160°E

10°S

20°S

30°S

40°S

INDIAN OCEAN

INDIAN OCEAN PACIFIC OCEAN

0 375 750 MILES

0 375 750 KILOMETERS

EXPLANATION

Total Petroleum 

System

Assessment Unit

AFRICA

AUSTRALIA

CHINA

Assessment

area

Figure 1. Locations 

of four geologic 

provinces of Australia 

assessed in this 

study.
In the Browse Basin Province, the Paleozoic-Mesozoic Composite TPS was defined on the basis of oil and gas generated primarily 

from Upper Jurassic through Lower Cretaceous organic-rich shales that 

were deposited in restricted-marine environments. The Shelf and Basin 

Sandstone AU was defined within this TPS to encompass potential 

alluvial-deltaic, slope-channel, and basin-floor sandstone reservoirs.

In the Northwest Shelf Province, the Northern Carnarvon-Canning Mesozoic TPS includes oil and gas generated from Triassic and 

Jurassic organic-rich shales. The Fault-Structured Sandstone Reservoirs AU was defined within the TPS to include reservoirs ranging 

from alluvial-deltaic to deep marine sandstones and pinnacle and patch 

reefs. 

In the Gippsland Basin Province, the Cretaceous-Tertiary Composite TPS includes oil and gas generated from mixed terrestrial and 

algal (lacustrine and marine) sources. The Latrobe Group Clastics AU 

was defined to include mainly Upper Cretaceous to Paleocene sandstone reservoirs.

Resource Summary

The USGS assessed undiscovered conventional oil and gas 

resources in seven assessment units within four major hydrocarbonproducing geologic provinces of Australia (table 1). The resulting mean 

totals for conventional resources are (1) 4,701 million barrels of oil 

(MMBO), ranging from 2,534 to 7,660 MMBO; (2) 227,006 billion 

cubic feet of gas (BCFG), ranging from 107,050 to 392,067 BCFG; 

and (3) 7,652 million barrels of natural gas liquids (MMBNGL), ranging from 3,203 to 14,394 MMBNGL.

Of the mean oil total of 4,701 MMBO, about 64 percent is 

estimated to be in the Fault-Structured Sandstone Reservoirs AU of 

the Northwest Shelf Province (mean of 3,001 MMBO). Two AUs in 

other provinces are estimated to have potential oil volumes greater than 

500 MMBO: the Shelf and Basin Sandstone AU in the Browse Basin 

Province (mean of 633 MMBO) and the Malita Graben-Sahul Platform 

AU in the Bonaparte Basin Province (mean of 714 MMBO).

For the mean undiscovered gas total of 227,006 BCFG, about 58 

percent is estimated to be in the Fault-Structured Sandstone Reservoirs AU of the Northwest Shelf Province (mean total of 130,642 

BCFG). The Bonaparte Basin Province is estimated to have potential 

gas volumes greater than 50,000 BCFG (mean of 55,325 BCFG), and 

the Browse Basin Province is estimated to have potential gas volumes 

greater than 35,000 BCFG (mean of 38,490 BCFG). Overall, the 

assessment indicates that more than 97 percent of the undiscovered oil 

and gas resources are offshore.

For Further Information

Supporting studies of the geologic models and the methodology 

used in the assessment of Australia basins are in progress. Assessment 

results are available at the USGS Energy Program Website: http://

energy.cr.usgs.gov/oilgas/.

Australia Provinces Assessment Team: 

Richard M. Pollastro, Michael E. Brownfield, Ronald R. Charpentier, Troy A. Cook, Timothy R. Klett, Mark A. Kirschbaum, Janet 

K. Pitman, and Christopher J. Schenk.

Total petroleum systems 

(TPS) 

and assessment units (AU)

Field 

type

Largest 

expected 

mean

field size

Total undiscovered resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Bonaparte Basin Province, Paleozoic-Mesozoic Composite TPS

South Petrel Sub-Basin AU

Oil 18 43 77 138 82 42 112 268 128 1 3 7 3

Gas 1,197 1,882 4,365 9,193 4,804 57 133 283 147

Londonderry High-North Petrel 

AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0 0

Gas 1,076 5,886 10,431 17,600 10,905 72 127 215 133

Vulcan Sub-Basin AU

Oil 26 55 121 257 134 160 389 870 435 5 12 26 13

Gas 222 127 350 1,091 447 5 14 45 18

Malita Graben-Sahul Platform 

AU

Oil 103 329 668 1,259 714 360 757 1,474 815 11 23 45 25

Gas 7,071 15,328 34,896 70,159 37,791 1,014 2,492 5,778 2,825

Browse Basin Province, Paleozoic-Mesozoic Composite TPS

Shelf and Basin Sandstone AU

Oil 49 325 594 1,077 633 1,072 2,033 3,730 2,166 32 62 113 66

Gas 6,979 14,384 33,366 67,854 36,324 438 1,018 2,091 1,110

Gippsland Basin Province, Cretaceous-Tertiary Composite TPS

Latrobe Group Clastics AU

Oil 24 87 133 200 137 133 253 451 267 5 14 37 16

Gas 439 1,128 2,152 3,879 2,282 52 99 181 105

Northwest Shelf Province, Northern Carnarvon-Canning Mesozoic TPS

Fault-Structured Sandstone 

Reservoirs AU

Oil 165 1,695 2,880 4,729 3,001 1,911 3,464 5,964 3,640 80 207 572 256

Gas 14,960 64,637 120,995 209,534 127,002 1,431 2,777 5,001 2,935

Total conventional

 resources 2,534 4,473 7,660 4,701 107,050 213,563 392,067 227,006 3,203 6,981 14,394 7,652

Table 1. Assessment results for Australia’s four major offshore petroleum provinces.

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas fields, all 

liquids are included under the NGL (natural gas liquids) category. Undiscovered gas resources are the sum of nonassociated and associated gas. F95 represents a 95-percent 

chance of at least the amount tabulated. Other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. Largest expected oil 

field size in MMBO; gas is in BCFG. Shading indicates not applicable]