The U.S. Geological Survey recently completed an assessment of undiscovered
conventional oil and gas resources in all areas north of the Arctic Circle – and the numbers are a bit eye-popping.
In fact, the agency concluded that 90 billion barrels of oil, 1,669 trillion
cubic feet of natural gas and 44 billion barrels of natural gas liquids may
remain in the Arctic, awaiting discovery.
More than 70 percent of the mean undiscovered oil resource is estimated to occur
in five provinces:
- Arctic Alaska.
- Amerasia Basin.
- East Greenland Rift Basins.
- East Barents Basin.
- West Greenland-East Canada.
Three provinces are thought to hold more than 70 percent of the undiscovered
natural gas:
- West Siberian Basin.
- East Barents Basin.
- Arctic Alaska.
About 84 percent of the entire resource is expected to occur in offshore areas.
It is noteworthy that most of the resource is not under the North Pole but
closer to shore in areas that aren’t subject to territorial dispute.
“In our judgment, the undiscovered resources up there are concentrated between
the shoreline and the 500 meter contour line,” said AAPG member Don Gautier, USGS geologist and project chief for the agency’s assessment, dubbed the Circum-Arctic Resource Appraisal (CARA).
“We would think that most of that is within the 200 nautical mile limit in one
way or another,” he said.
Reviewing the Situation
The Arctic Circle encompasses about 6 percent of the earth’s surface, and the extensive Arctic continental shelf region may constitute the
largest remaining unexplored prospective hydrocarbon area, geographically
speaking.
More than 400 oil and gas fields already have been discovered north of the
Arctic Circle, primarily onshore and in Russia for the most part, Gautier
noted. They account for approximately 240 billion barrels of oil and
oil-equivalent natural gas.
This approximates 10 percent of the world’s known conventional petroleum resources (cumulative production and remaining
proved reserves).
The CARA included only resources determined to be technically recoverable using
current technology. Regarding the offshore, the assumption is the resources
would be recoverable even in the situation of permanent sea ice and oceanic
water depth.
The estimates include no economic considerations. The study results include no
reference to exploration and development costs, which would be considerable in
this generally harsh environment.
Although any meaningful development of these resources is years away, it is
perhaps fortuitous for the United States that the CARA revealed a sizeable
amount of the oil resource is off the coast of Alaska, where some offshore
drilling already occurs.
“About a third of the undiscovered oil was in the province we call the Arctic
Alaska province,” Gautier said. “This includes a lot of area of Chukchi Sea and part of the Beaufort Sea.”
Most of the undiscovered natural gas is thought to be concentrated in the
northern part of the western Siberian Basin, Gautier noted.
A major hindrance to Arctic exploration, particularly in the offshore areas, has
been the near-permanent sea ice – an obstacle to both seismic data collection and exploratory drilling.
However, the ice cap has melted to some degree – whether permanently or temporarily – which could usher in a whole new era for exploration.
The Northwest Passage, for example, was open all last summer, according to Ron
Macnab, Geological Survey of Canada (retired). He noted that for the first time
in recorded history, one could have sailed a major ship all the way through the
Passage.
A New Approach
Because of the dearth of seismic and drilling data in much of the Arctic, the
CARA program differed from the typical USGS resource assessment that relies on
discovery process modeling, prospect delineation and deposit simulation.
Instead, the CARA effort relied on a probabilistic methodology of geological
analysis and analog modeling.
Using a newly compiled map of Arctic sedimentary basins, the CARA team defined
geologic provinces, each containing more than three kilometers of sedimentary
strata, according to Gautier. Assessment units (AU) – mappable volumes of rock with common geologic traits – were identified within each province and quantitatively assessed for petroleum
potential.
A world analog database was developed that includes areas accounting for more
than 95 percent of the world’s known oil and gas resources outside the United States.
For each AU, the CARA team assessed the probability that a significant oil or
gas accumulation was present. Evaluation of the AU probability was based on
three geologic elements:
- Charge (including source rocks and thermal maturity).
- Rocks (including reservoirs, traps and seals).
- Timing (including the relative ages of migration and trap formation, as well as
preservation).
Each AU was ranked according to its AU probability. The AUs determined to have
less than a 10 percent probability of a significant accumulation (recoverable
volumes of a minimum 50 million barrels of oil and/or oil equivalent natural
gas) were not quantitatively assessed, according to Gautier.
He noted that in addition to the AU probability, the number of accumulations,
the size-frequency distribution of accumulations and the relative likelihood of
oil versus gas were assessed for each AU and combined by means of a Monte Carlo
simulation.
“The probabilistic results reflect the wide range of uncertainty inherent in
frontier geological provinces such as those of the Arctic,” Gautier said.