|Map of the assessment units (AUs) of the CARA is color-coded for mean estimated undiscovered oil. Only areas north of the Arctic Circle are included in the estimates. Black lines indicate AU boundaries. Source: USGS CARA. Click to enlarge.|
The US Geological Survey (USGS) has completed a geologically-based assessment of the oil and gas resource potential of the Arctic, the Circum-Arctic Resource Appraisal (CARA). (Earlier post.) The researchers in the effort concluded that about 13% of the world’s undiscovered oil and 30% of the world’s undiscovered gas may be found there, mostly offshore under less than 500 meters of water. A paper on the work was published in the 29 May issue of the journal Science.
Undiscovered natural gas is three times more abundant than oil in the Arctic and is largely concentrated in Russia, the researchers concluded. Oil resources, although important to the interests of Arctic countries, are probably not sufficient to substantially shift the current geographic pattern of world oil production, they said.
The Arctic Circle encompasses 6% of Earth’s surface. One-third of that area is above sea level, one-third is in continental shelves beneath less than 500 m of water, and the final third is deep ocean basins historically covered by sea ice.
Many onshore areas have already been explored; by 2007, more than 400 oil and gas fields, containing 40 billion barrels of oil (BBO), 1,136 trillion cubic feet (TCF) of natural gas, and 8 billion barrels of natural gas liquids had been developed north of the Arctic Circle, mostly in the West Siberian Basin of Russia and on the North Slope of Alaska.
Deep oceanic basins have relatively low petroleum potential, but the Arctic continental shelves constitute one of the world’s largest remaining prospective areas. Until now, remoteness and technical difficulty, coupled with abundant low-cost petroleum, have ensured that little exploration occurred offshore. Even where offshore wells have been drilled, in the Mackenzie Delta, the Barents Sea, the Sverdrup Basin, and offshore Alaska, most resulting discoveries remain undeveloped.—Gautier et al.
|Map showing the AUs of the CARA color-coded for mean estimated undiscovered gas. Source: USGS CARA. Click to enlarge.|
The CARA only considered accumulations with recoverable hydrocarbon volumes larger than 50 million barrels of oil or 300 billion cubic feet of gas (50 million barrels of oil equivalent, 50 MMBOE). The project excluded unconventional resources such as coal bed methane, gas hydrates, oil shales, and heavy oil and tar sands. The project did not consider technological and economic risks; resources were assumed to be recoverable even in the presence of sea ice or oceanic water depths.
A new map delineating the Arctic sedimentary successions by age, thickness, and structural and tectonic setting provided the basis for defining assessment units (AUs), which are mappable volumes of sedimentary rocks that share similar geological properties. The CARA defined 69 AUs, each containing more than 3 km of sedimentary strata—the minimum thickness necessary to bury petroleum source rocks sufficiently to generate significant petroleum. The CARA team analyzed each Arctic AU to determine the geologic properties most likely to control the sizes and numbers of undiscovered petroleum accumulations.
On an energy-equivalent basis, we estimate that the Arctic contains more than three times as much undiscovered gas as oil. The estimated largest undiscovered gas accumulation is almost eight times the estimated size of the largest undiscovered oil accumulation (22.5 BBOE versus 2.9 BBO) and therefore more likely to be developed. The aggregated results suggest there is a high probability (>95% chance) that more than 770 TCF of gas occurs north of the Arctic Circle, a one in two chance (50%) that more than 1547 TCF may be found, and a 1 in 20 chance (5%) that as much as 2990 TCF could be added to proved reserves from new discoveries. For comparison, current world gas consumption is almost 110 TCF per year. The median estimate of undiscovered gas is a volume larger than the volume of total gas so far discovered in the Arctic and represents about 30% of global undiscovered conventional gas.—Gautier et al.
Overall, the CARA team concluded that the Arctic region contains 22.8 billion barrels of oil with 95% probability, 275 billion barrels of oil with 5% probability, and 95.5 billion barrels of oil with mean probability.
The CARA team concluded that the largest total concentration of petroleum was in the Alaskan Platform (AU code AA1), with a 95% probability of 13.866 billion barrels, a 5% probability of 47.426 billion barrels, and a mean probability of 27.851 billion barrels of oil. The largest single concentration was estimated to be 4.288 billion barrels (mean) in the North Barents basin (EBB3).
Donald L. Gautier et al. (2009) Assessment of Undiscovered Oil and Gas in the Arctic. Science Vol. 324. no. 5931, pp. 1175 - 1179 doi: 10.1126/science.1169467