West Texas Intermediate futures for January delivery, which expires today, fell to $35.73 (-0.92%), while Brent crude dropped to $36.40 (-1.30%). Prices of both types of crude fell to levels not seen since 2009 and 2004 respectively.

Investors are concerned over the persistent supply glut and prospects of exports from the U.S. after elimination of a forty-year old export ban. Iran is also preparing to boost production now that the sanctions are lifted.

Data showed on Friday that despite plunging prices U.S. rig count rose by 17 to 541 after four weeks of declines.