NEW YORK (MarketWatch) -- Energy stocks fell harder than the broad market in early action on Friday, on the heels of comments about a business slowdown from oil service sector leader Schlumberger . The Amex Oil Index fell 3.2% to 826, greater than the 2.5% loss by the Dow Jone Industrial Average The Amex Natural Gas Index dropped 2% to 370. Schlumberger fell 10% to $47.75 after matching Wall Street's third-quarter earnings target.