Cuba has historically been dependent on oil imports. As of 2011, Cuba had proven reserves of a mere of crude oil and 2.5 trillion cubic feet of natural gas, and mostly used oil for power generation. In 2010, Cuba produced 51,000 barrels of crude oil a day (Kb/d) in 2010 in onshore or shallow near-shore development, "mostly heavy, sour (sulfur-rich) crude that requires advanced refining capacity to process." Offshore exploration in the North Cuba Basin had revealed the possibility of an additional of technically recoverable crude oil, 0.9 billion barrels of natural gas liquids, and 9.8 trillion cubic feet of natural gas. As of 2011, Cuba had six offshore petroleum development projects with foreign oil companies Petrovietnam (Vietnam), Petronas (Malaysia), PDVSA (Venezuela), Sonangol (Angola), ONGC (India), Repsol (Spain), and Statoil (Norway).