Critics of environmentally risky oil projects proposed for deep undersea and Canada's tar sands got new ammunition last week when a report labeled those ventures and others as the industry's most financially questionable pursuits.

The new report, published by the Carbon Tracker Initiative (CTI), identifies a host of drawing-board oil projects that would cost a combined $91 billion over the next decade—and that would lose money if lower demand, carbon restrictions or other factors forced crude prices below $95 a barrel. Many of the projects need oil prices to settle substantially higher than $110 a barrel to break even, CTI said.

It's the latest in a string of offerings from London-based CTI, a non-profit that has been highlighting climate-related risks and costs that they believe are not being addressed by fossil fuel companies or reflected in financial markets. Through a pair of earlier reports, the group helped popularize the notion that fossil fuel companies could end up with valueless "unburnable carbon," or stranded assets, if governments move to limit global warming to 2 degrees Celsius.

By highlighting the financial risk of specific mega-projects in its latest work, CTI hopes to convince more Wall Street analysts and oil company investors to pressure ExxonMobil, BP, Shell and others to justify the expenses or cancel development.

"I think by drawing attention to the questionable nature of some of these projects, this gives investors more power to challenge the [money] that's being spent on them," said Andrew Grant, financial analyst for CTI and primary author of the new report. "The more [spending] that gets cancelled, the fewer projects that go ahead, the less carbon emitted into the atmosphere."

In response to pressure from shareholders, several major oil companies have already announced plans to cut or keep capital spending flat this year, and some have recently shelved or deferred big-ticket projects. In lieu of that spending, oil companies have been increasing stock dividends and buying back shares to placate investors.

The CTI study, however, includes a list of the 20 largest projects that are high-carbon, high-risk and high-cost, and are still being considered by Exxon, BP, Shell, Chevron, Total, Eni and ConocoPhillips—the world's largest publicly traded oil companies.

Eight of the listed projects are ongoing or proposed for the oil sands in Alberta, Canada, where companies have been extracting tar-like heavy crude known as bitumen. Another eight involve drilling in deep or ultra-deep waters off the coast of Brazil, Africa and the U.S. Gulf Coast. Three are in the Arctic.

CTI's report reveals cost data and breakeven calculations that oil companies have been reluctant to share. The group used information from Rystad Energy, an Oslow-based industry consulting firm that maintains a database of oil and gas ventures around the world.

"This is something more specific that investors can ask about. In particular, 'what are your plans for the projects identified in this report? Do they really make sense?'" said Ryan Salmon, senior manager of the oil and gas program at Ceres, a nonprofit devoted to sustainability advocacy. "It might prove to be a way of putting the onus on the companies to really justify their analysis and their reasoning on these sorts of projects."

By investing billions of dollars in those projects, the oil companies are making a long-term bet on high oil prices, said Salmon of Ceres. That prediction may ultimately prove true, he added, but "there are a variety of factors that could change that equation."

The price of Brent crude—the European oil that serves as the benchmark for world crude sales—has spent most of this year between $100 and $110 per barrel. It peaked above $145 in 2008, but dove to below $40 when the recession slowed demand. The U.S. benchmark crude, West Texas Intermediate, is trading below $100 a barrel.

Many oil companies have acknowledged the existence and perils of global warming, but they have pursued increasingly expensive oil development projects because they believe global oil demand will continue to ratchet higher, driven mostly by the expanding economies of China and India.

"They may not have the ability to even imagine a world where the oil that is on their balance sheet would not be allowed to be produced," said John Fullerton, founder of Capital Institute, a group focused on paving the way toward a sustainable economy. "It's a big mental shift, and they have this 'replace our production' culture—'damn the torpedoes, we're going to produce more oil next year than we did this year, one way or another.'"

Fullerton, a former managing director at JP Morgan, noted that CTI's approach uses the investment world's own preoccupation with shareholder returns to question the oil industry's pursuit of expensive and risky projects that are also among the most carbon-intensive.

"I really give them a lot of credit for essentially playing to the financial markets," Fullerton said of CTI. "I think it's working...the stranded asset/carbon bubble issue is now on the table, and part of the public debate. And even though the debate isn't being played out as a moral issue on its face, it's going to be increasingly difficult to not get to the moral issue."