Almost every financial market decline creates some kind of buying opportunity. And now that opportunity consists of oil stocks, says MarketWatch columnist Jeff Reeves.

"With crude oil prices in a funk, you may not get such an opportunity in years," he writes. U.S. oil prices fell to a three-year low Tuesday. Sluggish demand, thanks to stagnant economies overseas, and buoyant supply have sent prices down 28 percent from their June highs.

The stocks of oil-related companies have slumped as a result. The S&P Global Oil Index, which includes shares of 120 of the largest oil & gas producers in the world, has dropped 8 percent so far this year.

"What investors should ask themselves is whether the outlook is going to change, and whether now may be a good time to snap up oil stocks on the cheap," Reeves writes.

Goldman Sachs rates oil service companies Schlumberger, Halliburton and Baker Hughes as "buys," he notes. They are seen benefiting from their operations outside the United States, where drilling costs are lower and oil prices are higher.

"Be patient as oil prices are low and wait for stocks to bottom out," Reeves proclaims.

"There's no way to know for sure if this is the bottom, but in the long run, investors can have confidence in geographically diverse service stocks that have staying power."

Morningstar lists five other energy stocks to consider, CNNMoney reports.

• Chevron, the second biggest U.S. energy company after ExxonMobil. It sports a 3.7 percent dividend yield.
• Royal Dutch Shell, Europe's biggest oil company. It has a dividend yield of 5.5 percent.
• Magellan Midstream Partners, a pipeline owner. Its dividend yield is 3 percent.
• Spectra Energy Partners, another pipeline owner. It offers a 4.2 percent dividend yield.
• AmeriGas Partners, the country's largest retail propane marketer. It has a 7.7 percent dividend yield.

Related Stories:

• IHS' Yergin: 'We Have Entered a New Era' of Lower Oil Prices
• JPMorgan's Kelly: 'Falling Oil Prices Positive for US Economy'