If you only pay attention to energy exploration and production (E&P) companies, then you’re missing a huge part of the industry’s profit-making potential. Refiners such as Phillips 66 (NYSE: PSX) and HollyFrontier (NYSE: HFC) provide a market for the production from oil and gas E&P specialists, and they aim to profit on the spreads they can earn between what they pay for crude oil and what they receive for the refined energy products they make.