Sector adds to gains ahead of inventory data By: MarketWatch March 11, 2009 at 09:23 AM EDT Energy stocks add to big gains from the previous session in early activity as investors look toward the latest weekly petroleum supply data and lower oil prices. Read More >> Related Stocks: Cameron International Chevron Corp Exxon Mobil Halliburton Co Petrobras - Petroleo Brasileiro S.A. Schlumberger Ltd Transocean Ltd