Combustion (IMAGE) Kazan Federal University Caption The problem of petroleum depletion becomes more and pertinent every day. As deficits arise, non-traditional and heavy oils, including bitumen and shales, emerge as the focus of extensive research. Globally, they account for about 60 to 70 percent of explored reserves. For Russia, it's also over 60 percent. Credit Kazan Federal University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.