Several key weakspots can be gleamed from this article.

 

1) Oil must be sent to Kharg Island from mailand, most likely underwater pipeline.

 

2) if oil is being pre-processed to meet certain specifications, it is not difficult to determine where it is going, since refineries are set up to run certain types of crudes.

 

3) Tankers can only dock at the large platforms since water depth is probably to shallow closer to the island.

 

4) Oil must be pumped from Kharg Island to the platforms, involving another set of underwater pipes. May also have capability to divert oil from mainland to platform. KEY point if true.

 

5) pumping stations are key

 

So we have several options, take out the pipes or pumping stations and the oil can't flow, take out the platform and the ship's can't dock, take out the processing plant on mainland and the oil is unsellable.

 

Best option, contaminate the crude while tanks are full at Kharg Island or sabotage processing lab analysis. No space to pump back to mainland, can't ship it out either because of commercial specs. Not a shot fired and Kharg Island is effectively shut down.

Gee - and with an embargo on spare parts - it might be months before Iran can pump again.  Thus - hitting the Mullahs in the spot most vulnerable - their checking accounts.

 

Of course, quick resolution of the issues at hand - 15 hostages and that pesky nuke program - could lead to a restart of the flow of that black gold.