Sept 6 (Reuters) - Top U.S. natural gas producer EQT Corp said on Tuesday it would buy Quantum Energy-backed THQ Appalachia I LLC and associated pipeline infrastructure for $5.2 billion, as it looks to take advantage of strong commodity prices.

A surge in global natural gas prices following Russia's invasion of Ukraine has benefited U.S. natural gas producers and encouraged deals in the industry as companies try to scale up.

EQT will pay $2.6 billion in cash and about $2.6 billion in stock to THQ Appalachia, which is owned by privately held natural gas producer Tug Hill and has net production of around 760 million cubic feet per day.

The deal will add an estimated 800 million cubic feet per day of gas equivalent production, EQT said, adding it will also acquire assets of XcL Midstream, a pipeline operator that moves THQ Appalachia's gas to market, as part of the transaction.

Shares of EQT were marginally up in extended trading after the company doubled its share repurchase authorization to $2 billion and raised its 2023 debt reduction target to $4 billion. They have more than doubled this year.

Reuters on Monday reported that EQT was in advanced discussions to buy THQ Appalachia I.

RBC Capital Markets served as the financial adviser to EQT for the deal, while J.P. Morgan Securities and Wells Fargo Securities advised THQ.

Upon the closing of the deal, expected in the fourth quarter, Wil VanLoh, founder and chief executive officer of Quantum Energy Partners that backs THQ, will join EQT's board.

Last year, EQT acquired another privately owned natural gas producer, Alta Resources, for $2.9 billion, including debt.

(Reporting by Shariq Khan and Rithika Krishna; Editing by Shinjini Ganguli)