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 rose by nearly 2% on Thursday after the Federal Reserve's large cut in U.S. interest rates helped global benchmark Brent crude recover from its lowest in nearly three years hit last week. Brent futures rose to $74.

Brent crude futures for November fell 34 cents, or 0.46%, to $73.31 a barrel by 0015 GMT, while WTI crude futures for October declined to $70.49 a barrel, down 42 cents or 0.59%.