Dean Orrico, chief investment officer at Toronto-based Middlefield Group, said current SEC rules have kept some investors on the sidelines.

A change "will cause investors - whether they be super majors or investors globally - to more seriously consider investing in the oilsands here," Mr. Orrico, who runs OilSands Canada Corp., a mutual fund investing exclusively in oilsands companies, said on the sidelines of the fifth annual Insight Information oilsands conference.

"If that happens, a whole bunch of reserves off the book come on the books. That allows investors who are looking at getting exposure to the oil industry saying, ‘These are now real assets.' Here in Canada we are comfortable with this asset class, but I assume there are foreign investors who aren't going to look at these seriously until the SEC allows these companies to recognize them for accounting purposes."

Under current SEC rules, in place for decades, oil companies are prohibited from including the oil extracted from the oilsands in their estimation of proved reserves, a key measure of an oil company's worth.

But the U.S. regulator invited public input on the issue Dec. 12 as part of a broad review of oil and gas reserves' disclosure requirements, acknowledging that "given the scarcity of relatively accessible petroleum reserves that companies can extract using conventional techniques, [they] are increasingly looking to resources that are more difficult to access due to their geologic or geographical location or require specialized extraction techniques.

"Should we consider eliminating the current restrictions on including oil and gas reserves from sources that require further processing, e.g. tar sands," the SEC asks in a so-called ‘concept release' document.

"What physical form of those reserves should we consider in evaluating such a framework?"

Lobbying to change the rules has been under way for years. Many have speculated that such a change by the influential regulator could have a substantial impact, providing the catalyst for even more aggressive investment in the deposits by reserves-challenged oil majors such as Exxon Mobil Corp., which could buy out minority shareholders in Imperial Oil Ltd.

Investment banker Robert Mason, managing director, TD Securities Inc., however, sees only a marginal impact from an SEC reclassification of oilsands reserves.

"Could it make a little bit of a difference for some companies if there was some positive reserves recognition changes? Yes," he said. "Overall, though, I think most of the companies that are here, focus on what they ultimately think they are going to recover. The importance of being able to call it proved or probable reserves, or to be able to lump it into the rest of the oil reserves, as opposed to disclosing it separately, I am not sure will make a huge difference."

The Canadian Association of Petroleum Producers is asking the SEC to make two key changes, said vice-president Greg Stringham. The lobby group supports re-classifying oilsands reserves as oil reserves, rather than under a separate mining category, which would make it "simpler and easier for investors to understand that this is oil, regardless of the extraction technique," he said.

It would also like to see a change in the current requirement that bitumen reserves be valued based on a price as of Dec. 31. Because bitumen prices tend to collapse at the end of the year, when demand for asphalt weakens, the rule can result in huge reserves writedowns, as was the case in 2005. CAPP said the SEC should instead use an average price for the year.

The SEC's public input period ends Feb. 19.

Mr. Orrico said he expects any SEC change to be implemented this year.