Total reserves: 0.5 trillion BOE
The resource that comes with the lowest external cost might be the oil we left behind, back when energy was a lot cheaper. Drillers typically end up extracting just a third of the oil in a given field, in part because when they drain reservoirs they also decrease the pressure that pushes oil to the surface, making it more expensive to extract the remaining barrels. In the U.S., abandoned oil fields may still contain a staggering 400 billion barrels of residual oil; worldwide, the figure is probably in the trillions. Extracting all of it is economically impossible, but advances in enhanced oil recovery, or EOR, could boost extraction rates to as high as 70 percent.
EOR could add perhaps half a trillion “new” barrels worldwide. And it could also carry a substantial environmental bonus. One of the most promising EOR methods involves “flooding” oil reservoirs with CO2, which dissolves into the oil, making it both thinner and more voluminous, and thus easier to extract. Once the oil is extracted, the CO2 can be separated, re-injected into the field, and sequestered there permanently. An aggressive strategy in which CO2 is captured from single-point sources (such as power plants or refineries) and pumped into oil fields could increase U.S. oil output by as much as 3.6 mbd while sequestering nearly a billion tons of CO2. And depending on the method, EOR can have an EROEI as high as 20:1.
EOR can’t entirely bridge the gap--but in a perfect world, we would at least begin by tapping those barrels, along with the oil--equivalent barrels of natural gas. That way, we would be using the least damaging resources first and saving the worst barrels for later, when (if all goes well) future engineering innovations will let us extract and consume them more safely and efficiently.
But of course, we don’t live in a perfect world. For now, oil producers will do what they have always done, which is to extract oil as cheaply as they can. And oil consumers will follow suit, buying the cheapest energy they can. We may eventually ask the market to take the true costs of production into account, perhaps by way of a carbon tax or some kind of climate regulation. Or we may not. Energy policy has never been particularly far-sighted. There is little chance that the transition to a clean-energy economy will be entirely clean. It will require trade-offs and compromises, and the cost of those trade-offs and compromises will rise with every year that we wait to get serious about moving away from oil.
Paul Roberts is the author of The End of Oil: On the Edge of a Perilous New World.
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