Source: Pioneer Natural Resources; Sands Weems, photographer.

Before oil prices plunged last year, America was in the midst of a real oil production boom. It had been a remarkable renaissance as U.S. oil companies reversed decades of oil production declines, which pushed the country's production over the top, leading the U.S. to claim the crown as the world's No. 1 oil producer. The most surprising thing about the boom was that big oil was late to the party as production growth was largely fueled by smaller exploration and production companies.

The early leaders of this boom are, in my opinion, the best exploration and production stocks to buy. However, there are five emerging exploration and production companies worth watching, as each has compelling upside. My only concern right now is how well these companies can handle low oil prices, which is why these are watchlist-worthy, but not at the top of my buy list at the moment.

1. Pioneer Natural Resources (NYSE:PXD)
With its positions in Texas' Permian Basin and Eagle Ford Shale, Pioneer Natural Resources is sitting on an enormous amount of oil and gas. The company estimates that its proved reserves plus its net resource potential totals 11 billion barrels of oil equivalent, or BOE. For perspective, that's enough oil equivalent to meet America's entire oil consumption for over a year. That large resource base is expected to drive 15% compound annual production growth for Pioneer Natural Resources at the current projected oil price. That said, lower oil prices have slowed Pioneer down, so the company needs to get its costs even lower so that it can drive profitable growth should oil prices remain weak.  

2. Concho Resources (NYSE:CXO)
Like Pioneer, Concho Resources has a premier position in the Permian Basin. The company estimates that it is sitting on 3.7 billion BOE of total resource potential. Despite the steep drop in oil prices, Concho is expected to grow its production by 18%-22% this year largely due to a 20% savings in well costs from just last year. That said, the company still has some work to do on costs, which would enable the company to create even more value out of its acreage position as oil prices improve.

3. Whiting Petroleum (NYSE:WLL)
Whiting Petroleum's future is built upon oil production growth outside of Texas, as the company is the leading producer in North Dakota's Williston Basin. In addition, the company has an emerging position in the Niobrara shale of the Rockies. The company sees tremendous future value creation from both plays, as it has 7,500 future well locations in North Dakota, which at a $6.5 million well cost will earn the company a 54% internal rate of return at $60 oil. Meanwhile, it has another 6,700 locations in the Rockies, which can be drilled for $4.5 million apiece and drive a 40% internal rate of return at $60 oil. That said, Whiting will really benefit as oil prices rise and its costs continue to drop as that combination would really boost its returns.

4. Continental Resources (NYSE:CLR)
Like Whiting, Continental Resources is a very large Williston Basin producer and it has massive acreage position totaling nearly 1.2 million net acres that will keep it busy for years. At the company's current $7.7 million well cost, it can earn a 42% rate of return at $65 oil. For perspective, that's actually better than the returns it was earning at $80 oil as its previous well costs of $9.6 million resulted in just a 38% rate of return. In addition to its high return acreage in North Dakota, the company has an emerging position in several compelling oil and liquids plays in Oklahoma, as it controls 134,000 net acres in the STACK, 31,000 net acres in the Cana, and 480,000 net acres in the SCOOP. Combined, these plays are expected to deliver 16%-20% production growth in 2015, with the potential to deliver strong double-digit growth for years to come even at current oil prices.

5. Oasis Petroleum (NYSE:OAS)
A third Williston Basin producer, Oasis Petroleum controls more than a half-million net acres in that premier oil play. However, unlike the rest of the companies on this list, its plan is to keep production roughly flat in 2015 as it waits for costs to come down and oil prices to improve. As that happens, the company should be able to return to high-growth mode, which previously saw the company grow its proved reserves by a 62% compound annual growth rate from 2011 to 2014.

Investor takeaway
Shale-focused exploration and production companies have noticeably slowed their growth rate over the past year due to weaker oil prices. While prices have started to improve, these companies really would benefit from a further boost in the oil price in order to drive much more meaningful growth in the years ahead. The best stocks for that scenario are Pioneer Natural Resources, Concho Resources, Whiting Petroleum, Continental Resources, and Oasis Petroleum, as all have prime positions in the premier shale plays to go along with improving well returns in the current oil-price environment. As a result, all have the potential to deliver really robust returns as oil prices improve.