When it comes to long-term investing in the oil and gas sector, heavyweights such as ExxonMobil (NYSE:XOM), Chevron Corp. (NYSE:CVX), ConocoPhillips (NYSE:COP), BP Plc (NYSE:BP), and Shell (NYSE:SHEL) tend to hog the limelight. However, overlooking mid-cap oil and gas stocks (market-caps between $2 billion and $10 billion) can mean leaving plenty of money on the table. Although these smaller companies tend to receive less analyst coverage as compared to large caps, they offer more growth opportunities than large-cap stocks but exhibit less volatility…
