Quote from Sparohok:
Abqaiq is enormous and it's more than just a transfer point. They do water separation and treatment, gas recovery, hydrotreating, desulfurization, pumping, storage, etc. A very large bomb could certainly disrupt operations there but it wouldn't shut in a significant amount of Saudi production. To do that they'd need WMDs.
As we've seen in Iraq there are much more vulnerable parts of the oil infrastructure - pipelines. That's where I'd expect the next round of attacks. Not nearly as dramatic but much more effective.
Martin