The BSE benchmark Sensex was trading 312 points in positive territory at 17,658 a short while ago. Earlier, the Sensex surged over 287 points in early trade today.The 30-share barometer, which had gained 33 points in the previous session, shot up by 287 points, to 17,634.Similarly, the wide-based National Stock Exchange index Nifty gained 89 points, at 5,327.