The continent of Antarctica is distinctive in myriad ways, including its massive ice cap, mountain peaks and intriguing penguin population.
It also has the distinction of being the only continent in the world where an oil exploration well has never been drilled.
And because of myriad reasons, if the drill bits do begin turning in this remote locale, it won’t be anytime soon.
But at least one geologist believes personal bias, politics or fears of hostile environments should not be the reason for the delay.
Let’s talk geology, says David Macdonald, professor of petroleum geology at the University of Aberdeen, who will be doing just that at the AAPG International Conference and Exhibition in Perth.
In fact, the continent is protected from any mineral exploration -- including oil -- until the 2040s under the terms of the Madrid protocol to the Antarctic Treaty. The international treaty has been signed by most of the key countries capable of conducting oil exploration, according to Macdonald.
Given the huge ice sheet covering the continent, very little geology is exposed. Offshore geophysical data have been collected for scientific purposes but lack detail -- at least the kind needed for oil exploration.
Typically the seismic lines are tens of kilometers apart.
Gondwana Aftermath
The general geology can be summarized in a relatively simple manner.
“If you look down on the South Pole, you have a continent that looks like a tadpole, and the head is called East Antarctica or Greater Antarctica,” Macdonald said. “The geology is largely pre-Cambrian shield area where you have rocks going back to nearly 4,000 million years.
“This part of Antarctica is sort of the central remnant of Gondwana, as every other Gondwana continent was attached to this part of Antarctica at least a bit before migrating away,” Macdonald noted.
“There are some sedimentary rocks in East Antarctica and some sedimentary basins,” he said. “But they’re not very big because the continental shelves of East Antarctica are extremely narrow, probably the narrowest in the world. They also tend to be more than 1,000 meters water depth and don’t have the same sort of structures as other continental shelves.”
Another oddity is that the shallowest part of the continental shelf around most of Antarctica is the outer part because the shelf actually slopes backward toward the continent. This is due in part to the weight of the large ice mass bearing down and depressing the center of the continent.
Another factor comes into play during periods of extreme glaciation. When sea level is lowered, the continental shelves are scoured by ice, and the scouring is more intense on the inner portion.
The tail of the “tadpole” is known as West Antarctica or Lesser Antarctica. It’s largely a Mesozoic volcanic arc and is dominated by andesites, granodiorites and such.
The third major zone of the continent is a sort of low trough that separates the two bits of Antarctica. One side of the trough is the Transanarctic Mountains, which rise to 15,000 feet.
There are no exposed rocks on view within this central zone, but data offshore indicate the rocks are probably Mesozoic with some Cenozoic occurrence, according to Macdonald.
The expression of the trough coming through the middle of the continent is the Weddell Sea in the Atlantic sector and the Ross Sea in the Pacific sector. Most of the “exploration thinking” has focused on these two large sedimentary basins, according to Macdonald.
“This is where the petroleum geology starts to come in,” he said. “We know from the onshore geology in West Antarctica in the Antarctica peninsula area that there are black mudstones, which have source potential.
“There are source rocks of Jurassic age probably kicking around over a lot of this sedimentary basin area,” Macdonald said. “We know they’ve got organic carbon content up to maybe 4 percent.”
A Few More Obstacles
If you’re tempted to pack your field clothes and long johns and call a meeting of investors, calm down.
It goes downhill considerably from this point.
“As to risk potential, you have to risk it extremely highly because of the large amount of volcanics,” Macdonald cautioned. “Any sandstones we see of this age tend to be very volcanic-dominated and have very low porosity.”
Maturation is another thorny issue.
There’s been considerable volcanism in the area, so there’s a possibility a lot of the source rocks are over-mature as a result, according to Macdonald. On the other hand, the younger source rocks are likely to be under-mature.
The likelihood of no trapping mechanisms adds still more risk to potential exploration activity.
“Since the start of the Tertiary, there’s been little collisional tectonics or anything that would create structure,” Macdonald said. “So in a lot of these things there’s considerable risk of no traps.
“When you add up all the risks -- particularly on reservoir maturation and structuring -- you end up with something quite prohibitive,” he noted. “And that’s before you start looking at environmental factors like depths of continental shelves and the ice that covers the seas around Antarctica for nine months of the year.”
The area produces some whopper icebergs.
“The icebergs are two to three orders of magnitude bigger than anything dealt with in other areas,” Macdonald said. “The biggest icebergs they deal with at Hibernia Field off Canada wouldn’t register on the radar in Antarctica.”
Taking an ‘Honest Look’
The significant downside to exploring doesn’t necessarily mean ignoring what may or may not be there hydrocarbon-wise.
“My argument is Antarctica is a continent worth protecting,” Macdonald said, “but it’s worth protecting by doing an honest assessment of what the risks and likely returns for any oil exploration would be.
“The risks are so high no normal oil company would be tempted to try their luck there,” he said. “The only reason anyone might drill a well there would be to make a political point rather than in hopes of any economic gain.
“My idea to assess it is just take an honest look at it instead of shying away and saying it’s a protected continent, and we shouldn’t even be thinking about it,” Macdonald said.
“Maybe a lot of people will relax when we take an honest look at it.”