The value of about 75 shale-focused U.S. producers based on their reserves fell by a median of 25 percent by the end of 2014 compared to 2013, according to data compiled by Bloomberg. Photographer: Daniel Acker/Bloomberg (Bloomberg) — A decision by Whiting Petroleum Corp., the largest producer in North Dakota’s Bakken shale basin, to put itself up for sale looks to be the first tremor in a potential wave of consolidation as $50-a-barrel prices undercut companies with heavy debt and high costs. For the first time since wildcatters such as Harold Hamm of Continental Resources Inc. began extracting significant amounts of oil from shale formations, acquisition prospects from Texas to the Great Plains are looking less expensive. Buyers are ultimately after reserves, the amount of […]