Shell has kept mum about its colossal miss in the U.S. Arctic Ocean last summer, but geologists who have studied the region for decades say a natural gas "flush" may long ago have swept out the oil from the Burger prospect where Shell sank a single, unsuccessful well after seven years of effort.
The theory also suggests that Shell, which announced in September it would abandon its star-crossed quest after spending more than $6 billion, might have had better luck drilling farther west.
That's the hypothesis of David Houseknecht, one of the region's foremost geologists and project chief for the U.S. Geological Survey's Energy Resources Program for Alaska.
Other experts say the idea helps explain why public well results and rock chips have shown a large amount of gas in the reservoir but limited evidence of oil. Unlike Alaska politicians who jumped at the chance to blame federal regulations for Shell's decision to abandon the Arctic, the scientists say the answer is simply a matter of geology — the oil just wasn't there in big volumes.
Steve Wright, a former Chevron geologist who owns a geological consulting firm, called Houseknecht's idea the most credible theory out there. And if it's right, it means oil that was once at Burger went somewhere else.
Where that oil is now, and whether it can one day be produced, is anyone's guess.
"That's the $6 billion question," said Wright.
Betting on Burger
Houseknecht believes Shell would have better luck searching west of the Hanna Trough, an undersea structure that's considered an extension of the North Slope's oil-rich basin, with the same oil-holder source rocks.
Shell drilled three wells west of the trough starting in 1989 – Crackerjack, Popcorn and Klondike -- during the U.S. Arctic Ocean's first era of oil exploration.
The oil giant encountered "significant shows" of oil in each well, but not at levels Shell considered economical during the low oil prices at the time, said Houseknecht.
East of the Hanna Trough, Shell completed the original Burger well in 1990 -- part of the food-themed campaign -- about 70 miles northwest of the Inupiat village of Wainwright.
The company found a huge amount of gas there, and a little oil that wasn't promising because it was located below the reservoir, said Houseknecht, who has analyzed well data from that original effort, as well as rock samples archived at the Alaska Geologic Materials Center in Anchorage.
The results and other information prompted the U.S. government to report in 2004 that the huge Burger reservoir could be filled "completely with gas," about 14 trillion cubic feet of it.
But when Shell returned to the Chukchi Sea in 2008 to once again hunt for oil, it revisited its old data using new technology and collected new information from updated seismic studies.
After the new look, company officials thought they had an elephant field at Burger. Geologists said the prospect had the right ingredients: promising source rocks, a high-quality reservoir where oil could flow, and a trap that had captured natural gas. Those clues suggested that a large oil leg, or pool of oil, might lie underneath the gas much like at Prudhoe Bay, the largest field discovered in North America.
It turns out Shell was wrong. After Shell punched the Burger J well about 8 miles from the original Burger hole, the company's operations director in the Americas, Marvin Odum, announced the "disappointing" results in September.
Shell had found "indications" of oil and gas but not enough to support more exploration.
The right ingredients
What was Shell thinking? Its officials aren't talking.
Tom Homza, Shell's principal regional geologist for the Alaska effort, said he couldn't discuss the project.
Shell doesn't share such "commercial and proprietary" information, said Curtis Smith, a Shell spokesman in Washington, D.C.
Bob Swenson, former state geologist for Alaska, said Shell, with its new information, gambled on a promising spot.
"It's a probability game and they had a high probability of things being right," he said.
Dry holes are drilled all the time, even in mature basins with thousands of previous wells, he said. It took nine wells to discover Prudhoe Bay, a 24 billion-barrel reservoir. Meanwhile, just six wells have been drilled in the Chukchi Sea, including the Diamond exploration well by Chevron in 1991.
"In areas where you have very little subsurface information and very few wells, it's like looking at a satellite image of Mars and saying, 'Is there water there?'" said Swenson.
"So to say Shell did something wrong is not a correct statement. What they did right is, they got another hole in the ground and some more data to help us firm up the hypothesis" about the gas flush.
"It turns out the oil leg was not there," Swenson said. "But it turns out it was there at one time."
The gas flush
According to Houseknecht's theory, a massive amount of gas formed in the foothills of the Brooks Range perhaps 90 million years ago when dinosaurs roamed the region.
It swept north, forcing oil out of some reservoirs, including where the Burger well was drilled.
The "gas flush" theory is widely accepted by geologists and has occurred elsewhere, including in Oklahoma. In Alaska, it explains why some areas of the Slope contain large amounts of oil but reservoirs just miles away are filled only with gas -- but with geologic evidence that oil was once there.
It explains why oil seeps can be found on the North Slope surface: It oozed upward after gas forced it from leaky reservoirs.
And it means the oil at Burger could have been pushed to the north, where it may still exist in a subsurface trap, Houseknecht said. Or it could have vanished eons ago after percolating to the surface, where microbes devoured it.
Meanwhile, the area west of the trough would have been protected, with the undersea trough acting as a barrier that stopped the gas flush and kept oil locked in traps, he said.
More data to come
Other Arctic Ocean wildcatters that snatched up leases during the blockbuster Chukchi Sea lease sale in 2008 may have staked their bets on the "gas-flush" concept, Houseknecht said.
ConocoPhillips and Statoil partnered on leases around the 1989 Klondike well that showed several signs of oil, a prospect they renamed Devil's Paw.
Kirk Sherwood, a geologist at the Bureau of Ocean Energy Management who helped write the 2004 report on the Burger field, said Houseknecht's theory is plausible. But he also said there may be numerous opportunities for oil on both sides of the trough, where huge reservoirs similar in size to the one beneath Prudhoe Bay can be found.
"The disappointment at the Burger J well doesn't condemn the Chukchi Sea planning area," he said. "The potential for oil in other untested structures besides the Burger play is still very high."
There is also risk on both sides of the trough, Sherwood said. Klondike contains "world-class source rock" for producing oil, but that source rock ends at Klondike and there are questions about whether oil could have migrated to the Crackerjack well.
Why didn't Shell pursue a second well, such as at Crackerjack?
Perhaps — after several years of costly struggle, growing public opposition and steep regulatory hurdles — Shell lost the will to keep trying, geologists said. With oil prices crashing and the global glut suggesting a turnaround might be years away, it may have came down to economics, said Houseknecht.
The Burger field was the closest of the prospects to the community of Barrow, where Shell staged supplies and manpower.
The other prospects were roughly another 40 miles away, and some were farther, a costly distance for an offshore drilling effort where materials and manpower are hauled on helicopters and ships.
"If you look at the map you can probably get a clue, because the farther offshore you go the more expensive it is to operate," Houseknecht said. "One possibility might be that they wanted to stay as close to shore as possible for the first well drilled since 1991."
But that's only speculation, since Shell isn't talking, he said.
More details are expected in September 2017. That's when rock chips and well data from Burger J will be publicly available, according to officials at the Bureau of Ocean Energy and Management.