Natalia Bratslavsky/iStockphoto/Thinkstock

The U.S. oil and gas industry witnessed an uptick in merger and acquisition (M&A) activity in 2013, with a particularly dynamic last quarter of the year, according to a new report by PricewaterhouseCoopers (PwC).

Between October and December there were 182 M&A deals closed, worth a total of $115.9 billion. Of these, there were 51 deals with values exceeding $50 million each, totalling $41.7 billion. This was a 154-percent increase from the total deal value registered in the third quarter of 2013, when it reached $16.4 billion from 43 deals. There were eight "mega deals," worth $26.4 billion, compared to three deals of a similar size, worth $6.4 billion, in the previous quarter.

RELATED: TransCanada ponders rail shipments if Keystone XL pipeline gets rejected

However, compared to the final quarter of 2012 the total deal volume fell 36 percent, while deal value went down 29 percent. Overall, last year's deal volume dropped from the 212 deals worth $152.8 billion in 2012, PwC found.

The outlook for 2014 remains positive, with predictions for a sustained interest in oil and gas M&A activity, the report said. Doug Meier, PwC's U.S. energy sector deals leader, commented that U.S. oil and gas industry M&A activity has maintained a relatively robust level thanks to the rapid development of the sector. Lately, companies have been concentrating on portfolio optimization, moving away from sectors that bring low returns and focusing extra efforts on more profitable segments, he added.