Beneath the Tar Sands Is Even Dirtier Oil, and Industry Is Salivating over It

The price of crude oil has slumped to its lowest point in six years, and that has sent some major oil companies scrambling to get out of expensive tar-sands projects in Alberta, Canada.  Shell has pulled out of one of its largest lease applications, and Petrochina is attempting to get rid of its tar-sands assets.  Environmentalists have watched the slowdown with great hope.

Yet at the same time, some of those very same companies are positioning themselves to tap into an even more dirty and expensive kind of oil in Alberta: bitumen carbonates.

The little-known bitumen carbonates are a far more difficult-to-mine, more unconventional form of the molasses-like bitumen that’s already being extracted from the tar sands.  In Alberta the carbonates are in a deposit called the Grosmont formation, and most of it is underneath the tar sands themselves.  The bitumen soaking the surface-level tar sands was once pushed up through the layers of limestone and dolomite that comprise the carbonates, and much of that bitumen is still trapped within the layer of porous rock.  The carbonate rock resembles Swiss cheese, and in images of samples, black bitumen oozes from its holes.  The Grosmont is estimated to contain about 500 billion barrels of oil, three times as much as the proven reserves in the tar sands above it.  Industry insiders have a tendency to mention it in the same breath as Saudi Arabia’s mammoth Ghawar oilfield.

Shell, Husky, tar-sands giant Suncor, and the dreaded Koch brothers have all snapped up leases in Alberta’s bitumen carbonates.  In mid-March, the mineral rights for a portion of carbonates were sold at auction for three-and-a-half times the average price for such leases, indicating great confidence in their profit-making potential, if not in the short term, then in the long term.

Despite decades of attempts, though, no one has yet found a way to profitably mine them. Looking at pictures of the oil-filled rock, it’s easy to imagine why these deposits are hard to mine.  As in the tar sands, the bitumen in the carbonates is almost solid, meaning it has to be mixed with regular light crude and other solvents just to be made liquid enough to move through a pipeline (this mixture is that infamous “dilbit,” or diluted bitumen).  So, this oil needs more oil just in order to be transported elsewhere.  In addition to that, the dolomite’s fissures and holes (called “vugs” in geological parlance) are so uneven and unpredictable that companies haven’t figured out how to send drilling equipment through it:  some holes are so large that they could swallow a drill.

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