When, and where, oil is too cheap to be profitable

If oil prices keep falling, at some point it's not profitable to pull it out of the ground. But we're not there yet, according to an analysis of production costs by an energy consulting firm.

In fact, even if the Brent price index falls another 20 percent from Friday's closing price—to $40 a barrel—just 1.6 percent of the world's oil supply would represent unprofitable production.

Energy consultant Wood Mackenzie analyzed production data from 2,222 oil fields around the world to see just how much further oil prices would have to fall to make them "cash negative"—costing more to operate than the oil is worth. That price can act like a brake on production, according to Wood Mackenzie analyst Robert Plummer.

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"Once the oil price reaches these levels, producers have a sometimes complex decision to continue producing, losing money on every barrel produced, or to halt production, which will reduce supply," he said.

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A derrick hand removes the the plastic caps off the threaded ends of pipe used in the drilling process in Knox County, Ohio.

Among the first to shut off the spigots would be U.S onshore production from the trickle of crude emanating from aging, so-called stripper wells. Wood Mackenzie estimates there's about a million barrels per day coming from a collection of older wells that produce only a few barrels a day. The cost of keeping them going varies between $20 and $50 a barrel. So if the price of crude drops below $40 a barrel, some producers may decide to stop pumping.

Below $40 a barrel, the next likely production slowdown would come from Canadian tar sands fields, which start to lose money when the Brent price hits the high $30 range. But turning the flow off and restarting it again is a complex process, involving injecting steam into the ground, which makes it costly to restart, according to Wood Mackenzie. On the other hand, fuel represents a major cost for oil sands production, so lower oil prices could help lower overall production costs.

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In the U.K., North Sea oil fields start to lose money below $50 a barrel, according to the analysis. But many of them are older fields reaching the end of their lives, so stopping production could mean slowing down for good. That decommissioning process can be expensive, so some companies may decide to operate at a small loss rather than spend the money to close down operations, the analysts noted.

Production costs also include government taxes and royalties, which could be reduced or suspended if those governments want to keeping production going. Some of the "heavy oil" projects in Latin America, including those in Venezuela and Colombia, become money losers at lower prices, which could spur those governments to offer some kind of royalty relief, the analysts said.

Overall, the analysis found, the impact of $40 oil on global production would be very small, based on data covering some 75 million barrels a day of production. At $50-a-barrel Brent, only 190,000 barrels a day is unprofitable, representing just 0.2 percent of global supply. Seventeen countries supply oil that is cash negative at $50, with the main contributors being the United Kingdom and the United States.

At $45 a barrel, only 400,000 barrels per day, or just 0.4 percent of global supply, are unprofitable. Half of that is from conventional onshore production in the U.S. And at $40 a barrel, just 1.5 million barrels per day represents unprofitable production, or just 1.6 percent of global supply. Most of that production comes from several oil sands projects in Canada.

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Even when a field becomes cash negative, it doesn't necessarily prompt producers to shut down right away, said Plummer.

"The first response is usually to store oil produced in the hope that the oil can be sold when the price recovers," he said. "Operators may prefer to continue producing oil at a loss rather than stop production, especially for large projects such as oil sands and mature fields in the North Sea."