This article was written by Oilprice.com, the leading provider of energy news in the world. Check out these other articles.

Investors in oil stocks are finding out lately just how painful an oil supply glut can be. At a time like this though, one key for investors is to look at the companies that are buckling down and running their businesses efficiently. The companies that will thrive in today's environment are those that run productive wells at a low cost. And one of the best places to find these firms is in the Eagle Ford Shale area.

The list of operators in the Eagle Ford Shale area is long, but one firm that stands out is Devon Energy (DVN -1.44%). Devon is an upstream oil and gas producer with some assets in Canada and the Rockies, but most of its operations are in Texas.

Devon has an attractive valuation, a significant growth profile, and much of the restructuring work that other energy companies are going through right now has already been done by Devon. The company started restructuring in 2010, including divesting the bulk of its offshore and international assets. The company then used the improved balance sheet to focus on the North American markets just as the shale revolution was taking off. It now has major holdings in Eagle Ford, the Permian Basin, and the Anadarko Basin.

Roughly half of the company's 2015 production is hedged at $91 a barrel, and as such, the company's fortunes are less pegged to oil prices right now than many of its peers.

Devon has highly productive acreage with dirt cheap production costs, especially in the Eagle Ford. Analysts are enthused about the stock, but while the price has moved up somewhat in the last few weeks, there is still plenty of room to run from here.

Another top choice in the Eagle Ford is Marathon Oil (MRO -2.21%). The stock has started to see upgrades from analysts in the last month or so but the stock price has actually come back down in recent weeks, offering a good entry point for investors. Marathon's assets in Eagle Ford, Bakken, and other areas are low cost, with inventory up to potentially twenty years. As a result, while investors were not thrilled with the most recent earnings report, this stock would be more of a long-term play. Management is prudently reducing costs and cutting capex, all while improving the efficiency of drilling. From an earnings standpoint, the next couple of years may be still tough, but for the long-term investor, Marathon offers a lot of upside.

Finally, Carrizo Oil & Gas (CRZO) has also started getting more positive attention from the Street, due to its diverse production and acreage portfolio. The company has solid proven assets in the Utica Shale region of Ohio, the Niobrara Formation in Colorado, the Marcellus Shale, and the Eagle Ford Shale. Carrizo has excellent scale, low costs, and plenty of liquidity on the balance sheet. This last point is especially important, as it may allow Carrizo to make some targeted acquisitions in certain areas at today's rock-bottom prices.

There has not been as much M&A activity as one might have expected so far in E&P, probably as a result of a wide gap on asset valuations between buyers and sellers, but sooner or later that will change.

Now these companies are not the only good investments in Eagle Ford – in fact per barrel production costs are coming down across the region and this appears likely to continue. However, for serious E&P investors, these three stocks are definitely worth some consideration.