A few weeks ago, I suggested that two divergent trends would shape the oil market over the next few years: the chaos of Venezuela, where production continues to decline, and the success of the US shale industry in Texas and North Dakota where production is set to grow rapidly.

A number of readers were quick to point out there is a third potential disruption — the possibility of a revolt in Iran against the Islamic Revolution and the mullahs. 

Until very recently, such a revolt seemed out of the question. The regime was entrenched and appeared able to survive any new sanctions imposed by the US. Oil exports might fall and proceeds might decline still more because of the discounting necessary in conducting an illegal trade, but the Islamic Revolution would not be broken.