Energy stocks are under stiff pressure for the third straight session. On Monday the energy sector slid 1.3%, yesterday it dove 2.4%, and today it is down another 1.3%. National Oilwell Varco (NOV 70.33, -2.05), Cameron International (CAM 49.01, 1.78), and Hess Corp (HES 77.63, -2.20) are in some of the worst shape this morning. Diamond Offshore Drilling (DO 70.85, -0.27) and Rowan (RDC 38.57, -0.14) have managed to limit losses, though.