An aerial image shows a natural gas flare after sunset outside of Williston, North Dakota in this March 12, 2013 file photo. Oil drillers in North Dakota’s Bakken shale fields are losing out on more than $100 million per month in lost revenue as the amount of natural gas flared continues to balloon, despite near-universal efforts to curb the controversial practice, according to a study to be released July 29, 2013. Picture taken March 12, 2013. To match Exclusive BAKKEN-FLARING/ REUTERS/Shannon Stapleton (UNITED STATES – Tags: BUSINESS ENERGY ENVIRONMENT)