An Iranian war-boat fires a missile during the ‘Velayat-90′ navy exercises in the Strait of Hormuz in southern Iran on December 30, 2011.

The fact that some of the world’s largest oil and gas reservoirs are 100% owned and operated by national oil companies could benefit international oil companies if economic sanctions imposed on Iran constrain the country’s petroleum production, Moody’s Investors Service said in a recent note.

“As most IOCs have no or very limited exposure to Iran in terms of their overall production, higher prices triggered by a supply squeeze from the sanctions on Iran would benefit their upstream operations considerably.”

The analysts went on to say that the gains from higher prices would outweigh any adverse effects on IOC’s downstream businesses, which typically account for a smaller portion of these companies operating profits and cash flows.

The overall impact on Iran’s crude export volumes is likely to be limited, however, as major importers like China and India would be reticent to reduce their supply by anything more than the minimum amount required to receive a waiver from US sanctions, said Moody’s, though they did not identify that “minimum amount.”

Importantly, the consortium developing the enormous Shah Deniz natural gas field off the Caspian coast of Azerbaijan – in which National Iranian Oil Company subsidiary Naftiran Intertrade holds a 10% stake – would not have its operations impacted as the US has granted the project an exception because it is deemed a strategically important European natural gas supply source.

Beginning in 2017, the Shah Deniz 2 project is set to produce an incremental 16 billion cubic meters of gas per year – on top of the approximately 9 bcma being produced from stage 1. The consortium plans to make a final pipeline route selection in 2013. Europe imported 291 Bcm of gas in 2010, according to the latest BP Statistical Review of World Energy.

“We would expect the loss of hydrocarbon production resulting from a [Strait of Hormuz] blockade to be either partially or fully offset for the affected rated companies by higher oil prices for their other sources of production,” the analysts said. While the supply disruption associated with such a blockage would be substantial, the Strait would likely be reopened relatively quickly, the analysis predicted, presumably due to US intervention.