A couple of articles by Simon Watkins here. Now, he is quite biased and bitter about China/Russia's increasing influence in the middle east, but I think there are some keys points here.
1) China has been building up relationship with Saudi Arabia slowly for a long time
2) China and Russia have been coordinating in the Middle East
3) American presence is fading in the Middle East, as such, Saudis no longer have to abide by any price range that American president may seek to impose
4) Saudis and Iranian peace deal really does reduce Western influence in the middle east
5) Iraq has a lot of reserves and makes sense for China/Russia to use its connections with Saudis/Iranians to push out everyone else
6) There is a reason neocons want to have independent Kurdistan. It weakens the control of Sunni and Shiites block
Also interesting that America is now supporting the Turkish opposition so openly.