Dealmaking in America's oil patch plunged in Q4 as corporations preserved cash in the face of falling crude prices and tight capital markets.
The U.S. energy sector announced 42 deals worth $50 million or more for a total of $31.6 billion in mergers and acquisitions in the closing months of 2015, according to PricewaterhouseCoopers.
For the full year, 179 deals worth a combined $196.1 billion were announced, down from 278 deals worth $304.4 billion in 2014.
The declines in energy M&A came as global dealmaking across industries surpassed $5 trillion in 2015 for the first time on record.
"As oil prices stay lower for longer, cash flow will stay constrained resulting in companies operating in survival mode with a focus on realigning their strategies and business models," Doug Meier, PwC's U.S. oil and gas sector deals leader, said in a statement.
The cost of crude fell to 12-year lows in December after OPEC announced it would continue its policy of maintaining high production rather than cut output, which would support prices.
U.S. crude futures have since fallen as low as $26.19 per barrel.
M&A remained muted throughout much of last year as drillers held out hope for a rebound in commodity prices rather than part with assets at fire sale prices.
Energy companies also extended their lifelines by binging on debt and equity issuances in the first half of the year.
But equity offerings were down 17 percent year over year last quarter, while high-yield and investment-grade debt issuance dropped 48 percent and 22 percent, respectively, according to PwC.
PwC sees energy sector dealmaking increasing this year as some companies are forced into bankruptcy and as both private equity firms and oil and gas corporations with strong balance sheets go bargain hunting.
"For M&A activity to resume at a reasonable pace, it will take buyers who are patient and have long-term perspective on the potential value of the assets while it will take some motivation from sellers who have few other liquidity options and are able to get reasonable value under the circumstances," said Seenu Akunuri, PwC's US oil and gas valuation practice leader.
The upstream segment, comprised of companies that explore for and produce oil and natural gas, accounted for the largest number and volume of deals worth $50 million or more, with 21 totaling $9.7 billion.
Dealmaking in the fourth quarter slowed to a trickle in U.S. shale oil plays, where drillers use a process called hydraulic fracturing to bombard shale rocks with water, chemicals and minerals at high pressure to free oil and gas.
OPEC's production policy is seen as directly targeting these high-cost producers.
Texas' prolific Permian Basin attracted five deals worth a total of $1.5 billion. Just one deal worth north of $50 million was struck in other areas, including North Dakota's Bakken, the Northeast's Marcellus Shale, and the western Niobrara formation.