Bakken Oilfields

FILE - In this July 26, 2011, file photo, a worker hangs from an oil derrick outside of Williston, N.D. Justin Kringstad, the director of the North Dakota Pipeline Authority said proposed increases of tar sands oil from Canada likely will not have an impact on the state's soaring oil production. Kringstad said refinery destinations for the two crudes may differ because heavy sour crude from Alberta's tar sands is of lower-value and more difficult to refine than North Dakota's light sweet crude. (AP Photo/Gregory Bull, File)