Extreme Crude: Oil's Impossible Places

Brazil's quest for extreme oil may cost as much as US$ 1 trillion. That is a lot of money to invest in a such a risky proposition -- to retrieve oil that is miles deep underwater. But oil prospectors and producers around the world are on the prowl for extreme crude -- found in places that previous generations would not have dreamed of going.

The hunt for extreme oil proceeds apace in the ultradeep waters off the coasts of Ghana and Nigeria, in the sulfur-laden depths of the Black Sea, under the polar ice caps, and in the gummy tar sands of Venezuela’s Orinoco Basin and Canada’s McMurray Formation (see the related DISCOVER story, "The End of Easy Oil"). The Gulf debacle has shaken national governments, but it has hardly deterred them. Mexico is taking advantage of the fallout from the disaster next door—and the suspension of cross-border prospecting—to buy time for its national oil company, Pemex, which plans to beef up its own deepwater capabilities. A month after Deepwater Horizon exploded, the Australian government reaffirmed its commitment to ocean drilling, putting 31 offshore blocks up for bidding, 17 of them in deep waters. While pundits and regulators issue encomiums to safety, the most noticeable shifts in the “post BP” oil industry are a fat discount on rental rates for offshore platforms no longer needed in the Gulf and the exodus of idled rigs heading to other waters.

...What keeps Petrobras going is the size of the prize. Just the proven reserves in three different Brazilian pre-salt exploration areas total 10 billion to 16 billion barrels, the largest oil discovery in the Western Hemisphere in three decades. And that may be only the beginning. After drilling 13 more test wells, the experts now reckon that the pre-salt reserves sprawl over an oblong slab of more than 57,000 square miles of ocean—Brazilians call it “the blue beefsteak.” And the petroleum there is not the heavy, low-grade stuff that Brazil currently fetches from existing offshore wells, but light, sweet crude, the prize of hydrocarbons, preferred for jet fuel. _Discover

The microbes which created the oil in the Gulf of Mexico were fed ages ago by the land effluent of the Mississippi River basin Not so long ago -- in geologic terms -- Africa and South America were at hailing distance from one another. With a broad continental shelf between them, and with the Amazon feeding from the west and the Congo and other rivers feeding from the east, photosynthetic and other microbes between the continents fed very well indeed.

Those vast fields are relatively recent in origin, as the Earth thinks of time. It will take some good detective work to track down older, more ancient shelfs and feedwaters. But that is what the spirit of extreme crude is all about. That and going ever deeper, and after ever-tougher game.

Geophysicists have known for decades that plenty of oil and gas is hidden away below the oceans, but they were unable to see it clearly with traditional seismic techniques. Because salt is much less dense than rock, the sound waves surveyors use to scour the depths race through it at nearly three miles per second, twice as fast as it traverses the surrounding rock and sand. When sound waves pass from compact rock in the seabed to the pliant salt below, they kick into overdrive, scattering and distorting the seismic waves. The result is a blurry image that geophysicists compare to a snowy television picture, making it almost impossible to define the true size and position of the salt cap.

To sharpen the picture, Petrobras upgraded its toolbox with 3-D imaging. Traditionally, geophysicists take readings by sending sound waves straight down and straight back, creating two-dimensional pictures of slices of the earth that can be “read” like individual pages. But since salt can blur any given seismic image, exploration crews fired their seismic probe from various angles and then put all the images together to produce a three-dimensional view of the salt block. The technology helped them zero in on an intriguing section of seafloor in the little-known Santos Basin, off the coast of southern Brazil. To confirm the findings, Petrobras’s computer engineers have spent years developing software to correct for distortions—both sound wave reflections and seismic noise—that salt introduces in the readings. After multiple 3-D probes, they had a sense that something big was buried under the salt.

BP pioneered the exploration of oil and gas sealed beneath salt domes under the Gulf of Mexico, and potential pre-salt oil reserves of untold dimensions are currently being mapped along the west coast of Africa in the waters of Gabon, Angola, and Ghana. That area is a geologic mirror image of South America’s eastern flank, the two continents having separated when the supercontinent of Gondwana broke apart some 160 million years ago.

But Brazil may be sitting on the largest pre-salt resources of all, meaning that Tupi may represent both the pinnacle and the end point of this type of exploration. Finding and retrieving all this oil (and the associated natural gas) weighs heavily on the balance sheet. The first pre-salt test well took 14 months and cost $240 million, although more recent Petrobras pre-salt offshore wells have cost about $66 million each. Just operating a rig to drill in the pre-salt can cost up to $1 million a day. Industry insiders estimate that retrieval costs for Brazil’s proven pre-salt reserves could run as high as $1 trillion. _Discover

As geologists get better at finding oil and gas that require newer horizontal drilling approaches, engineers will develop yet newer approaches to finding and producing from even tougher deposits. It is a progression that is demanded by modern day economic and political factors which dominate the price of oil -- rather than by any meaningful or impending shortage of liquid fuels.