March 31 (Reuters) - Exxon Mobil Corp expects rising first-quarter results across its three major businesses, with an at least $2 billion improvement from prices for oil and gas driving profits, the company signaled in a securities filing on Wednesday. The filing, detailing factors that affected the business, showed higher oil prices sequentially lift its oil and gas operating results by between $1.6 billion and $2 billion over the fourth quarter. Natural gas pricing added another up to $700 million to operating profit, it indicated. The filing also signaled a gain of as much as $1 billion in refining from better margins and unsettled derivatives. Exxon’s chemicals business is seen recording an up to $600 million boost over fourth quarter results in its chemicals business from better margins. (Reporting by Jennifer Hiller and Shariq Khan; Editing by Anil D’Silva)