EQT Corp., the largest natural gas producer in the United States, agreed Monday to buy former entity Equitrans Midstream Corp., bringing back together Appalachian-based giants in what executives said was a game-changing opportunity.

The all-stock transaction, estimated Monday at around $5.5 billion, would hold 27.6 Tcfe of proved reserves across nearly two million net acres. Net production would be around 6.3 Bcfe/d net, with 8 Bcfe/d-plus of gathering throughput across 3,000-plus miles of pipeline.

EQT in 2018 had spun off Equitrans to focus on exploration and production. The all-stock merger on Monday was valued at around $5.5 billion, and it carries an enterprise value estimated at $35 billion.

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