Wall Street pros have nothing on retail investors who stake small sums of money monthly on undervalued small-cap stocks. Because the big guns mostly ignore them, these types of stocks can offer outsized opportunities for growth.

I screened for stocks under $3 billion in market cap with long-term earnings growth forecast to be at least 15%. One stock that floated to the top was oil and natural gas developer Halcon Resources Corp (NYSE:HK), whose focus is on the Woodbine, Eagle Ford, and Bakken shale regions. With substantial proven reserves that will support a program of growth, it posted a loss of a penny per share in profits, compared with a $0.10-per-share loss in the year-ago period. With analysts anticipating earnings growth 32% annually for the next five years and with a $2.0 billion market cap, it comfortably makes it into our range for potential investment candidates.

Of course, don't jump on a stock just for those reasons. It should just be a starting point for more research, as we need to look more closely to see whether analysts' faith in them is well-founded.

It's all wet On the back of strategic acquisitions such as the recently completed purchase of properties in the Williston Basin from Petro-Hunt and Pillar Energy, Halcon is moving to exploit those resources through a drilling program focusing on oil and natural gas liquids. It's an area where many exploration and production firms are finding profits these days as natural gas prices remain depressed.

The movement away from dry natural gas and toward liquids and oil started as a trickle but has quickly become a torrent. SandRidge Energy Inc. (NYSE:SD) was one of the industry's early movers, seeing the coming shift as early as 2008 and hedging all of its natural gas production for two years as it set the stage for the switch to oil. It subsequently acquired oil-focused Arena Resources but was soon joined by EOG Resources, Inc. (NYSE:EOG), which sold off non-core natural gas assets, and Chesapeake Energy Corporation (NYSE:CHK) in turning its attention to the more profitable liquids market.

Similarly, BHP Billiton Limited (ADR) (NYSE:BHP) just reported that its onshore NGL assets are growing, contributing to the 4% increase in volumes it saw at the end of the fourth quarter, while Range Resources Corp. (NYSE:RRC) reported a 41% spike in NGL production.

The stampede, in turn, is spurring additional investments by storage and transportation specialists that are investing in facilities to handle the increased production. Oneok Partners LP (NYSE:OKS) , for example, announced plans to invest approximately $465 million to $500 million between now and 2015 in the Williston on a new 95-mile pipeline and a new 100 million cubic-foot-per-day storage facility.