This map, from 1994, is a vivid representation of the course of the seaborne oil trade. To really appreciate the strategic significance, you have to imagine the US Navy patrolling and controlling the global commons on which passes this great commercial array.
While US naval power is justified in relation to "keeping the sea lanes open," the Navy's domination of the seas also gives it the capability of denying use to an adversary. It is a moral certainty that China sees this vulnerability. That has significance whatever the state of US war plans, which can change.
The chart below from BP gives the figures as of 2007 (click on the chart to get a larger version and to see the figures). As compared with the beauty above, which allows one to see at a glance the relative shares of the seaborne oil trade, the BP chart represents regression in chart making.
According to BP, the difference between China's 2007 oil production (3.73 mbd) and its oil consumption (7.86 mbd) puts net imports at 4.13 mbd. The chart on the right from the EIA shows Chinese imports a bit less than 4 mbd. The seaborne traffic is doubtless a large share of that.
The growth of Chinese imports would be nicely shown in a map like the one above, but it is lost in BP's too large "Asia-Pacific" region.
Not only can't you see the relative flows, but the BP chart is pretty tough to figure out. And there isn't a key to it that I could find. A simple table showing the breakdowns would be much clearer. Does it really help illuminate the subject to distinguish Canada, the United States, and Mexico but to throw China, India, Japan, and Austrialia into one big regional blob?
Now, let's be fair. These are pretty charts to look at. Unlike the other oil majors, BP at least bothers to convey vital information accurately to the public. Thank you for that. You get four stars for that. But dammit, man, get with the program and make better charts with the data that you have.