The refining business has largely thrived amid the oil price collapse and its bounty of cheap feedstock, but small “teapot” refineries haven’t been so lucky. Bloomberg Business News examines the case of Dakota Prairie Refining, a new 20,000-barrel-per-day diesel refinery in North Dakota that was built when high diesel-to-oil premiums guaranteed strong profits. Now that many Bakken shale producers are halting operations, however, the market for diesel fuel has dried up. Meanwhile, the diesel premium has fallen from $100 per barrel to below $18 since November 2014.