When you think about energy stocks, companies like ExxonMobil (XOM 0.23%) probably come to mind. While there are good reasons to invest in the U.S.-based energy giants, international competitors may have more to offer. That's because some of the best-performing energy companies happen to operate outside the United States. It's possible these businesses may have brighter futures, while their U.S.-based peers struggle.

Two such companies are Statoil (EQNR 2.77%) and Repsol (REPYY 0.37%), which, thanks to several promising discoveries and stronger portfolios, may have brighter futures among all the global energy supermajors.

Resilience in a tough environment for integrated majors
Due to narrowing spreads between domestic crude and international benchmarks, oil refining is a tough business right now. Business conditions are so tough that refining alone is bringing down earnings from big oil to an alarming degree.

ExxonMobil's earnings dropped 18% in the third quarter and 31% over the first nine months of the year, as opposed to the same periods last year. This is due almost entirely to Exxon's refining troubles. Exxon's downstream business, which includes refining activities, generated $592 million in earnings during the third quarter. That compares to $3.2 billion in earnings from the downstream segment in the same quarter last year, representing a $2.6 billion drop in downstream profitability year over year.

By contrast, Statoil and Repsol are holding up much better, even amid such a poor operating environment for refiners. Statoil's adjusted earnings actually increased in the third quarter versus the same period last year. Repsol's operating income fell 12% through the first nine months of the year, which certainly isn't a strong performance, but one that stands measurably better than ExxonMobil's.

Industry research supports bullish thesis
An extensive research report from Morgan Stanley analysts highlights many of the disparities between ExxonMobil and its smaller, better performing international peers. ExxonMobil is not only struggling with poor refining results, but its future is dim because its upstream portfolio has few promising start-ups. According to the research report, ExxonMobil is expected to produce just 2.6% annual growth in its upstream operations, below the 3.4% growth expected of the sector as a whole.

Meanwhile, analysts are much more bullish on Statoil and Repsol. Statoil is set to reap the rewards of having the largest upstream start-up pipeline among the global majors. Between 2013 and 2016, growth in upstream operating cash flows is projected to clock in at 3.8% through 2016, compared to 3.4% for the sector.

In addition, Statoil points investors to the fact that the company's recent discovery in offshore Canada represents the world's largest oil discovery this year. An additional discovery in the Norwegian Sea, which will result in Statoil drilling 20 to 25 exploration wells, means great results in 2014 and beyond.

For its part, Repsol is expected to benefit from having an upstream portfolio that contains the lowest portion of fields in decline in the industry. Moreover, Repsol has several projects just starting up, meaning future production and profits are likely to outperform those of the industry. Repsol's projected upstream production is pegged at 9% through 2016, which indicates the strength of its portfolio.

Stronger portfolios make international energy majors appealing
You may be tempted to automatically choose the largest and most visible companies when considering an investment in the energy sector. But for those willing to consider lesser-known international competitors, the rewards may be worth the effort. In particular, Statoil and Repsol are largely avoiding the pitfalls of crushing downstream operations that have severely affected ExxonMobil's results throughout the year.

In addition, Statoil and Repsol hold younger, more promising portfolios and have announced considerable discoveries that are likely to fuel outperformance in the years ahead. As a result, savvy investors may want to give preference to Statoil and Respol among the global oil supermajors, at least until ExxonMobil's underlying results improve.