It seems quite unlikely that we're looking at terrorism here. Terrorists want large numbers of casualties, much more than structural damage, so blowing up an oil refinery is not really their style.
There are reports that the fire broke out on a barge that was refueling at the refinery. I'm betting that this was an accident, just like the fire in Rhode Island.
Not exactly true. They want us hit economically, and what better way to do it than shut down our oil supply during a slow growth economy?