Unocol's become quite the hot property. The conventional wisdom is that these companies are looking to buy it's reserves, and offering a price that reflects some confidence in higher base oil prices for some time to come. At least that applies to Chevron. CNOOC may have other issues at heart, related to demand projections perhaps. Haven't looked into this yet.
Where reserves are concerned it's truly a global industry. I heard ExxonMobil's speak out strongly in favor of allowing this to happen if it gets that far, since what's good for the goose is good for the gander.
IMO China will look to meet as much of its anticipated future demand as it can internally, minimizing any import opportunities as much as is practical. IMO all these joint ventures that have been underway with Shell and BP, etc. will have just served to transfer production and marketing know how to a significant future competitor with little in return.
Charon