North America is awash in oil, so you'd think our local oil companies would be laughing all the way to the bank. But too much oil, and too little pipeline capacity, is wreaking havoc on oil prices. In this video, Fool energy contributor Aimee Duffy explains how it happens, what role midstream companies like Enbridge (ENB 1.09%) and ONEOK Partners (OKS) are playing, and what oil companies are doing to compensate.