based on conversations with my dad, the production facilities are vulnerable to people with knowledge of the system- not necessarily engineers, but even bright techs.
The Saudis, believe it or not, have a lot of their own folks running ARAMCO. Maybe not efficently...but if you can keep the plant going without blowing it up, you probably have enough knowledge/skill to blow it up if you want to.
An out and out attack by a squad/platoon sized element unfamiliar with the layout/technology might not do that much damage, but an inside job by four or five guys who smuggled in a truck/car bomb or two or four, and placed them where they would do the most good (bad) could.
I don't think the oil production is their target. They want to scare and force out the expats.
They want The Two Holy Mosques and must overthrow the ruling Royals. To do so, they must complete the driving away of foreigners.
the want a Koran based nation beholden only to Allah.