Exxon has also made plans to replace four coking unit drums in 2015 and add two new coker drums in 2017 at the Beaumont refinery, the sources said. The drums turn residual crude oil into petroleum coke, a coal substitute.
An Exxon spokesman, while declining to discuss possible plans for the Beaumont refinery, said the company is always evaluating growth opportunities.
Though many U.S. refiners have been incrementally adding capacity, Exxon's move could be the first major U.S. refinery investment since the sudden rise of shale production opened up a new era of bumper profits for the sector.
The Exxon investment, if made, would bolster the U.S. Gulf Coast's position as a top exporter of fuels to the world at a time when U.S. demand for gasoline and diesel is falling.