Iran has already started excavation in largest joint oil filed with Qatar in the Persian Gulf, General Manager of the Pars Oil and Gas Company Musa Souri said. “The excavations of oil wells in the South Pars Oil Field will bear fruit soon; two oil drilling rigs have begun working there and one of them in the joint fields; drillings of these fields have surpassed the depth of 1,500 meters inside the earth; in the meantime, the design, manufacturing and installation of marine constructions in the oil field have started too,” he underlined. While Iran is just extracting 35,000 b/d from the South Pars Oil Field, Qatar is excavating 450,000 b/d, official reports say. Oil reserves in Iran rank third largest in the world at approximately 150 billion barrels as of 2007, although it ranks second if Canadian reserves of unconventional oil are excluded. This is roughly 10 percent of the world's total proven petroleum reserves. Iran is the world's fourth largest oil producer and is OPEC's second-largest producer after Saudi Arabia. As of 2009 it was producing an estimated 4.172 million barrels per day of crude oil. Iran has more than a century of history in exploration and production activities; the first successful exploration well was Masjid Suleiman-1 on May 26, 1908. Since then, based on the latest oil and gas reports, 145 hydrocarbon fields and 297 oil and gas reservoirs have been discovered in Iran, with many fields having multiple pay zones. A total of 102 fields are oil and the remaining 43 are gas, and there are 205 oil reservoirs and 92 natural gas reservoirs. According to Iran Energy Balance Sheet (2009, in Persian), 78 of these fields are currently active, with 62 onshore and 16 offshore, leaving 67 fields inactive at present. Some 23 hydrocarbon fields lie in border areas and are shared between Iran and adjacent countries, including Kuwait, Iraq, Qatar, Bahrain, UAE, Saudi Arabia and Turkmenistan.