A bit more information here:

Although Venezuela still is a significant oil supplier to the U.S. its relative importance has been decreasing during the last 5 years, going from second to fourth place among U.S. import sources. This is due to the loss of production capacity of the Venezuelan oil industry, a decline brought about by the politicization of the state-owned petroleum company under Chavez. Not only has production capacity declined but also half of the Venezuelan oil exports to the U.S. can only be refined in the United States due to its physical properties. This means that Chavez cannot easily sell this oil to alternative clients such as China or India. For this to be possible these countries would have to build refineries capable of processing Venezuelan oil, something that would take at least three to four years to accomplish, even if they started today.

In parallel with this lack of flexibility Venezuela is facing a decline in its international monetary reserves since Chavez keeps raiding them. These monetary reserves only represent some six to seven months of imports at the current level since Venezuela is now importing close to $40 billion per year, mostly in food. Therefore, an interruption of oil income derived from the cut off of oil supplies to the United States would most probably cause the Chavez’s regime to collapse in less than a year as the result of internal protests, no outside intervention required.