Potential buyers are looking for companies with positive cash flow and eyeing books of undervalued assets, the firm BDO USA consulting firm concluded following a survey to chief financial officers.

The consolidation seen in 2011 and 2012 is expected to extend into 2013, according to Charles Dewhurst, a practice leader for the firm's natural resources industry group.

"Overall market conditions have created an environment conducive to M&A activity," Dewhurst said, driven by factors including the continued growth of the unconventionals sector.

But