Oil futures fell about 2 percent on Monday as signs of rising U.S. crude output continued to weigh on prices and an OPEC report showing high compliance with last year's landmark production-cut deal underwhelmed investors.
Global benchmark Brent crude futures were down $1.09, or 1.9 percent, at $55.61 a barrel by 2:34 p.m. ET (1934 GMT), near the low of the session.
West Texas Intermediate (WTI) crude futures ended Monday's session 93 cents, or 1.7 percent, lower at $52.93 a barrel, also near its lowest level for the day.
"The good compliance rate of OPEC seems to be priced in. The U.S. rig count from Friday is weighing, the numbers support the shale comeback story," said Frank Klumpp, oil analyst at Stuttgart-based Landesbank Baden-Wuerttemberg.