"""...citing U.S. oil production at 15 million barrels per day, according to the Washington Post, when the reality is 6.2 million barrels per day """
No, that Wa Post article does not state Romney made such a statement. H
Transcripts are available as to what Gov Romney actually did say in the energy speech in Hobbs, NM, where he repeated referred to North America as an entity, and said, "Were producing in North America about 15 million barrels a day", about which the Governor was entirely correct.
http://www.whatthefolly.com/2012/08/24/transcript-mitt-romney-presents-energy-plan-in-new-mexico/