The Eagle Ford is big. How big? Well, according to United States Geological Survey, the field could contain between 7 billion to 10 billion barrels of recoverable oil. If accurate, that would make the formation the largest onshore oil field ever discovered in the continental United States. Yet there could be a bigger play, even larger than the Eagle Ford, just a five hour drive north. 

Could this oil field dwarf the Eagle Ford?
Rumblings in the industry suggest that the Cline Shale, a small section of the West Texas Permian Basin, could dwarf even the mighty Eagle Ford. There're two reasons why investors should keep this play on their watch list.

First, it has huge potential. Based on early estimates provided by Devon Energy (DVN 0.78%), the Cline could hold as much as 30 billion barrels of recoverable oil. That's three times larger than the most optimistic estimates for the Eagle Ford. 

Second, the Cline is surrounded by several oil-rich formations. In other shale plays, operators can target only one or two hydrocarbon producing fields. In the Eagle Ford for example, the hydrocarbon-producing layer is about 150 to 300 feet thick.

In contrast, the Cline, and many other areas in the Permian Basin, feature two or more producing formations that are stacked vertically on top of each other. This allows operators to exploit oil from various depths with a single vertical well. The Wolfcamp and Cline layers alone span 1,300 to 1,800 feet in thickness. When you imagine four to six Eagle Fords mounted on top of one another, you start to understand why the industry is excited.

Source: Devon Energy Investor Presentation

Additionally, the Cline is practically in the energy industry's backyard. The surrounding region is dotted with pipelines and processing facilities, which should keep development costs down. Occidental Petroleum (OXY 0.89%) is stepping up to be the lead shipper in the area with the company planing to reactivate and expand its existing pipeline system. This should bring on an additional 75,000 bpd of takeaway capacity by the end of this year.

The smart money is moving in
While the play is highly speculative, a lot of smart money is moving into the Cline. Last year, Chevron (CVX 1.54%) bought over 700,000 acres in the Permian Basin from Chesapeake Energy for $7 billion. More than 150,000 acres of this purchase was in the Cline shale.

Apache Energy (APA 0.56%) is the largest landowner in the Cline with 520,000 net acres. The company has an estimated 642 million barrels of oil equivalent in reserves and is on track to drill 28 pilot wells this year.

Devon Energy has 389,000 net acres in the Cline, and the company is on track to drill 30 pilot wells this year. To fund this program, Devon sold a 30% interest in its Cline and nearby Wolfcamp shale assets to Japanese energy giant Sumitomo for $1.4 billion.

Other companies betting big on the Cline include Pioneer Natural Resources, Range Resources, and Firewheel Energy. Many of these companies are just ramping up their exploration programs. As the results from these efforts are released later this year, investors will have a better sense of the play's potential. 

Foolish bottom line
Let me be clear: the Cline is still a highly speculative play. Much of the formation has not been de-risked beyond a handful of core areas. Productivity can vary widely across the formation, and new shale plays often exhibit wildly optimistic projections early in development. Investors should be rightly skeptical of bold claims. 

But if the field can live up to anything close to the hype, then the Cline could yet rival the Bakken or the Eagle Ford. This is definitely a play investors should keep an eye on.