^^^No, corporate HQ is in San Ramon in a sprawling office campus. They have the former Enron buildings in Houston, though (so they likely have an even larger operation there). Makes sense - Houston is to oil/energy what the Bay Area is to tech.
In terms of refinery operations, I think the major presences are:
Houston (like ridiculous huge capacity)
Louisiana coast (again, ridiculously huge capacity...3,309,000 barrels a day capacity)
Rest of Texas cast (ridiculously huge capacity)
Metro Philadelphia (1,126,000 barrels a day capacity)
Los Angeles (973,000 barrels a day capacity)
Bay Area (819,000 barrels a day capacity)
Chicago Collar Counties (810,000 barrels a day capacity)
North of Seattle (618,000 barrels a day capacity)
OH from Toledo over to Cleveland (568,000 barrels a day capacity)
There are a couple states with multiple refineries that together have north of 300-400,000 barrels a day capacity, including OK and KY. There are also a few one-off large refineries in several cities:
Whiting, IN has a 405,000 barrel a day refinery, counted in Chicago's #s above
Rosemount, MN near St. Paul has a capacity of 320,000 barrels in its refinery
Linden, NJ outside of NYC has a refinery with 230,000 capacity
Elk Point, SD has a refinery with capacity of 400,000 barrels
Memphis has a refinery with capacity of 180,000 barrels
http://en.wikipedia.org/wiki/List_of...neries#Alabama