Actually, they've been working on the modifications for more like three years, maybe even a little longer. It will NOT make Whiting the largest refinery in the U.S., but it is a large refinery. The "upgrade" is intended to make the refinery capable of processing (more) "heavy" crude, as in sourced from Canadian tar sands. This crude comes cheap but requires significantly more processing to produce useful fuels. The bet is that this has an economic advantage overall and will provide a more reliable feedstock source. As long as "better" crude remains above $60 or so, BP will do well. At current prices they will do very well.
I hear that revamp is behind schedule. Problems include location. air and water permits plus
contract restrictions. It is unlikely that there will ever be a successful complement of people
to run the place. Just my opinion based on historical info. Running any percentage of asphaltic
crude ( tar sands oil) will bring challenges beyond imagination.