The oil and gas industry is usually divided into three major sectors: upstream (or exploration and production - E&P), midstream and downstream. The upstream sector includes searching for potential underground or underwater crude oil and natural gas fields, drilling exploratory wells, and subsequently operating the wells that recover and bring the crude oil or raw natural gas to the surface.

The upstream industry has traditionally experienced the highest number of Mergers, Acquisitions (M&A) and Divestitures. M&A activity for upstream oil and gas deals in 2012 totaled $254 billion in 679 deals. A large chunk of this M&A, 33% in 2012, was driven by the unconventional/shale boom especially in the US followed by Russia and then Canada.

The aggregate value of Upstream E&P assets available for sale (Deals in Play) reached a record-high of $135 billion in Q3 2013. The value of Deals in Play doubled from $46 billion in 2009 to $90 billion in 2010. With ongoing M&A activity, the level remained almost the same, reaching $85 billion in December 2012. However, the first half of 2013 saw approximately $48 billion of net new assets coming on the market. Remarkably, the total value of Deals in Play in Q3 2013 nearly tripled over 2009 to $46 billion, in less than four years.