Oil is traded in US Dollars worldwide. Countries who import oil need to keep hordes of USD on reserve. This keeps the USD from hyperinflation. If those countries no longer needed USD to buy oil imports, there's a good chance that the USD would hyperinflate.
In the past, every time a nation tries to get out from under the heel of the USD, the US invades them, destroys their infrastructure and installs a puppet regime. Time and time again. In order to justify the invasion and destruction, they tell the American people that the country is an enemy, and must be destroyed in order to protect America. What they mean is "American Interests". Just semantics to the typical American.
I don't see the US invading China or Russia any time soon. If China offers to protect any nation that wants to use the Yuan to buy oil, what would the US do?
Oh, right, sanctions. That's become a worldwide household word lately. But what if Europe, the Persian Gulf States and the Eastern world side with China and Russia? The recent US isolationist policies might just isolate the US.
On March 26, 2018, in the first hour of trading, 10 billion yuan national traded on the yuan-petro exchange. Not a bad start.
In a further push to expand the Chinese currency, the London Metals Exchange is planning to launch Yuan-denominated futures. One step at a time, the world's bully is being challenged.