The Brent/WTI spread has historically ranged between $4/bbl and $8/bbl, but it can expand or contract based on factors related to U.S. and international supply and demand conditions. For example, the Brent/WTI spread hit nearly $14/bbl in April 2011 when protests sparked market fears of significant oil supply disruptions in the Middle East.

Oil prices extended their recent recovery rally and rose more than 1% on Thursday as a large cut in U.S. interest rates and declining global stockpiles helped offset some of the demand concerns arising from weak consumption in China.

Commercial crude oil stockpiles excluding the Strategic Petroleum Reserve fell by 1.6 million barrels to 417.5 million barrels in the week ended Sept. 13 and were about 4% below the five-year average for the time of year,