Jan 28 (Reuters) - The U.S. upstream mergers and acquisitions market regained momentum after a mid-year slowdown in the fourth quarter of 2025 reaching $23.5 billion in announced deals and pushing full-year activity to $65 billion, analytics firm Enverus said ‌on Wednesday.

The rebound was driven by motivated buyers including refunded private equity teams, increased ​use of securitized financing and new international entrants competing for limited ‍assets, the Enverus report added.

International buying in U.S. ⁠upstream markets soared ⁠to a seven-year high of $7.4 billion in 2025 and accounted for about $6 billion ‌in the fourth-quarter, where buyers focused ​on Gulf of Mexico and Denver-Julesburg (DJ) Basin assets.

However, with Mitsubishi's recent $7.5 billion deal for the purchase of the ⁠U.S. shale production and infrastructure ‍assets of ​Aethon Energy, attention has returned to the core Haynesville region as international buyers continue to prioritize Gulf Coast gas, according ‍to the report.

The consultancy firm expects buyers to look at other options including Eagle Ford and Anadarko Basin options for gas exposure, with opportunities becoming sparse in Haynesville.

Deal flow in the fourth quarter highlighted stronger activity outside the Permian Basin, with Gulf ​Coast ‍gas pricing climbing and Appalachia remaining steady.

Enverus said that the largest deal in the fourth quarter was SM Energy's ​merger deal with Civitas Resources, that included significant holdings not only in the Permian Basin but also in the DJ Basin.

And another noteworthy merger in 2025 was that of Crescent Energy with Vital Energy.

Furthermore, Enverus expects 2026 to be marked by active upstream M&A, supported by private capital, ​ABS-backed buyers, and sustained international interest.

"With fewer top-tier Permian packages transacting, the market's center of gravity should continue to broaden toward gas-weighted plays and non-core regional opportunities," ‍said Andrew Dittmar, principal analyst at Enverus.

(Reporting by Pranav Mathur in Bengaluru)