Oil Refining - What's Left Over?

Asphalt is oil that has lost much of its mass because of weathering, eria feeding on it and so forth. It thickens overtime because it grades, because bacteria have fed off the lighter hydrocarbons,. The big ones are in the western hemisphere, up in alberta, canada. And invent as well, of course, their oil industries an mass. Its been for a qorin while, but they're oil wel much of it is essentially asphald too.