In this video, Motley Fool energy analyst Joel South tells us about three interesting companies in the oil and natural gas sectors. He discusses Clean Energy (NASDAQ:CLNE) and how it is on track to profit from an ever-expanding consumer infrastructure for natural gas in the U.S; Heckmann (NYSE:HEK), whose big merger announced this week is just the play it needs to boom after last quarter's major bust; and, finally, Magnum Hunter Resources (NYSE:MHR), a junior oil company whose Q3 near-miss in earnings may belie much deeper growth potential.