HOUSTON (Reuters) -Volatility across energy and equity markets spooked investors in the second quarter, slowing the pace of mergers and acquisitions in the U.S. upstream oil and gas sector, analytics firm Enverus said on Wednesday. 

   The slump in dealmaking follows a series of blockbuster takeovers by oil and gas majors in recent years, which culminated in a record $192 billion worth of deals done in 2023.

There were $13.5 billion worth of deals disclosed in the quarter ended June 30, marking a 21% drop quarter-over-quarter, Enverus said. The first half of 2025 saw a total of $30.5 billion change hands, which is a 60% decline compared with the same period of 2024.

"Volatility in commodity and equity markets raised a major yellow flag for M&A, slowing the pace of dealmaking," said Andrew Dittmar, principal analyst at Enverus Intelligence Research.  

Oil prices fell to multi-year lows last quarter after U.S. President Donald Trump unveiled an extensive list of trade tariffs in April, stoking concerns of a recession and a drop in fuel demand, and the Organization of the Petroleum Exporting Countries announced plans to unwind deep output cuts. Prices also jumped as conflict in the Middle East inflated traders' risk premium.

During the second quarter, U.S. crude futures hit a low of $57.13 a barrel on May 5, before swinging to a high of $75.14 on June 18, according to data from LSEG.

Houston-based exploration and production company EOG Resources bought Encino Acquisition Partners for $5.6 billion in May, taking the lion's share of deals done in the second quarter, according to Enverus. 

Viper Energy followed with its purchase of Sitio Royalties for $4.1 billion in June. 

Those two transactions accounted for over 75% of second-quarter deal value, Enverus said. 

"The engine of M&A over the last few years has sputtered and stalled, given there are just a few remaining targets," Dittmar said. 

Companies will eventually need to explore opportunities to buy assets abroad, in Canada or further afield in areas like Argentina's Vaca Muerta, he added.