US Refiners Sitting on a Mountain of Partially Processed Gunk

(Bloomberg) -- U.S. stockpiles of “unfinished oils” are sitting at the highest levels since 2007, rising 14 percent this quarter alone. This brings up two questions -- why is this happening? And more importantly, what exactly are unfinished oils?

The Energy Information Administration defines them as such: “All oils requiring further processing, except those requiring only mechanical blending.” Confused? No fear -- the category includes oils “produced by partial refining of crude oil and include naphthas and lighter oils, kerosene and light gas oils, heavy gas oils, and residuum.” Clear as mud.

The build-up of this gunk is a likely result of refinery turnaround season, when some crudes go through only one unit while a secondary one is getting some spring cleaning. It’s nothing for the oil market to worry about, says Mason Hamilton, an analyst at the EIA. “I would expect them to draw in the next few weeks,” he said.

To contact the reporter on this story: Laura Blewitt in Houston at lblewitt@bloomberg.net. To contact the editors responsible for this story: David Marino at dmarino4@bloomberg.net Mike Jeffers.