One of the most amazing things about the Middle East is that the oil is all located under Shia areas - especially where Shi'ite majorities live under a Sunni regime.
One exception - that used to fit the rule - is Iraq.
Have a look at this map:
The oil even in Saudi Arabia is all located in the Shiite area. It must be pointed out for the uninitiated that Saudi Arabia is not a country. The Sa'ud family is from Riyadh in the Nejd (basically the purple - Wahhabi - area).
King 'Abd al-'Aziz al-Sa'ud, the re-founder of the Sa'ud dynasty, conquered what is now Saudi Arabia in the first quarter of the twentieth century. (Yes, you read that right.) This includes both the 'holy land' - the Hejaz - which is Sunni, and the oil-bearing Shi'ite lands - al Hasa.
The al Sa'ud family belong to and are patrons of the fundamentalist Wahhabi sect and the Shiites of al Hasa are oppressed by them to this day. There were riots a few months ago but you didn't hear about it. In short, the legitimacy of the rule of the al Sa'ud over their own oil lands is marginal at best. I'd expect the local people would look to Iran or Iraq for protection.
Furthermore, the al Sa'ud family when they conquered the Hejaz drove out the Sharif of Mecca - the traditional Guardian of the Two Holy Cities and a descendant of Mohammed. Thus their claim to be the legitimate Guardian is also tenuous at best. The best claimant that I know of is the current King of Jordan. His ancestor, the first King of Jordan, was son of the Sharif and a companion of Lawrence of Arabia and he was placed on throne of the newly created Jordan by the British after WWI. Incidentally, today Jordan is a de facto protectorate of Israel.
Also incidentally, the grievance of al Qa'eda that American troops were based in the Holy Land is laughable at best - a glance at the map will tell you that American troops were guarding the oilfields, not Mecca.
Worse, Wahhabism is an al-Qa'eda-like fundamentalist sect and much of the funding for al-Qa'eda came privately from rogue princes of the Royal Family and other wealthy, well-connected individuals in Saudi Arabia. Worse still, I believe ISIS is funded - or used to be funded - by Saudi Arabia to fight the Syrian regime.
Add into the mix that
electric cars have reached the point where they are economically and technically viable.
That aside, one must be cautious, but it seems that comparatively moderate Shiite Iran - comparative that is to ISIS, the Taliban, or even Saudi Arabia - whether they know it or not, may have commenced a process rapprochement with America. They may even cooperate together on ISIS in what will de facto be a confidence-building measure. If they do it may well be a tipping point - when suddenly the balance of interest changes and we see the Shi'a, including not only Iraq but perhaps Iran, the Asad regime and even the (comparatively moderate) Hezbollah, lining up with the USA against Saudi Arabia.
This means all sorts of things. It means the USA can support the overthrow of Sunni Gulf emirates (Bahrain being the standout) by Shiite populations.
What will Saudi Arabia look like if that happens? Before the discovery of oil in al Hasa, Riyadh was a dirty, dusty, public toilet. Ashes to ashes...