Sometimes the hottest new play in oil and gas is the old one that someone just purchased.

That appeared to be the case as 2012 spiraled to a close. A flurry of deals in the second half of the year promised to manifest as E&P momentum in 2013—and beyond.

But the deals were also a signal that the industry appears to be restructuring in subtle ways. If tight-formation oil and gas is the future of the American oil patch, the economic tailwinds favor operators with deeper pockets.

This trend is ...