U.S. energy production is higher than it has been in decades, and as a result America's pipelines and processing centers are booming as well. Giant midstream companies such as Enbridge and TransCanada get a lot of press, but across the country there are many smaller, unheralded midstream outfits that may make great investments as well.

These companies may be potential buyout targets, destined for incredible growth, or about to go bust -- and they are worth a little research. With that in mind, today we look at two under-the-radar pipeline companies.

Smooth sailing ahead?
Atlas Pipeline Partners (NYSE:APL) was one of the best performing midstream stocks of 2011, but it was also one of the worst performing midstream stocks of 2012. Investors may be slightly more willing to tolerate erratic periods of unit price performance if Atlas was willing to increase its distribution. And it is.

Atlas announced that it's increasing its distribution to $0.58 per unit, marking the ninth increase in the past 10 quarters. As fellow Fool Matt DiLallo pointed out last week, a pattern of increasing distributions bodes well for share price over time.

Of course, the underlying fundamentals are what drive that distribution growth, and that's where investor focus should be this year. Atlas is taking steps to mitigate its year-to-year volatility by increasing its fee-based revenue.

At the end of last year, Atlas announced its plan to acquire Cardinal Midstream. More than 80% of Cardinal's gross margin is attributed to fixed-fee contracts. Absorbing those assets will go a long way toward smoothing out Atlas' performance.

Steady as she goes
Holly Energy Partners (NYSE:HEP) missed analyst expectations on EPS by $0.01 but beat revenue estimates by close to $10 million. The stock is up nearly 30% over the past 12 months, gaining 15.3% year to date.

Holly Energy has the sort of stable revenue that most midstream outfits are striving for: 100% of all revenues are fee-based, and it has zero exposure to commodity risk. The company benefits from a close relationship with HollyFrontier (NYSE:HFC). The Midwest refiner has a 42% stake in the midstream company and has signed long term pipeline and terminal agreements that guarantee stable cash flows for Holly Energy.

Holly Energy's assets include 2,900 miles of pipelines, 13 product terminals, and 11.8 million barrels of liquids storage. Great assets are only as good as their location, which in Holly's case is excellent. Spread from West Texas through the Midwest, Idaho and up through to Washington state, the company is poised to profit from growing energy production and shifting market dynamics.

Finally, Holly Energy Partners had its IPO in 2004. It has increased its distribution every quarter since, and its annualized payout now stands at $1.88 per unit, good for a yield 4.9% yield.

Foolish takeaway
These two stocks don't capture the headlines the way the midstream giants do, but they may be a great fit for your portfolio. Using Internet tools like My Watchlist can help you stay informed and figure out which one is best for you.

Fool contributor Aimee Duffy owns shares of HollyFrontier. Click here to see her holdings and a short bio. If you have the energy, follow her on Twitter, where she goes by @TMFDuffy.

The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.