You can't play the derivatives market in Canada unless you have somewhere between a $75000 and $200000 in liquid assets. Plus you have to pass an arbitrary test from some brokerage guy in Toronto containing all sorts of esoteric strategies you would never in your life play. Even if you intent to trade limited liability options contracts and even if you intent to play well in the money LEAPs, you can't unless you already have cash. You can't get a mortgage or business loan without cash. Basically the only people who don't need capital, are given a free ticket. Nice system if you are part of the club.
How is China "playing" oil? There Yuan is mostly pegged to limit consumer spending and make their exports cheaper. It is a successful development model followed by Europe post-WWII and South Korea. It is unlike Latin America's right-wing "free market" evolution (much of Africa too) that has left most of that continent truamatized while dictators and NY/London/Swiss bankers laugh all the way to the... bank. Maybe you know something I don't? lol, yeah right, you are a Conservative.
Oil is primarily USD denominated. If anything, China might trigger a run on the USD by withdrawing foreign investments and USD currency reserves. This would raise oil prices. But I'm sure Harper is more concerned about going hunting with Cheney and getting shot up the ass, than any of this subject matter.