Exxon Mobil Corp agreed to buy Pioneer for $59.5 billion, its biggest acquisition in more than two decades, in an attempt to dominate the shale oil industry. Exxon Mobil Corp will buy it all-stock at a price of $253 a share, according to the statement. The agreement paves the way for Exxon Mobil Corp's largest acquisition since his merger with Mobil in 1999 and is the world's largest corporate acquisition announced this year. If the deal is finalised, the merger will make Exxon Mobil Corp the largest oil company in the Permian basins of Texas and New Mexico and produce nearly 4.5 million barrels of oil equivalent a day, 50 per cent higher than the second-largest supergiant.