Consol Energy agreed to buy US rival Dominion Resources’ Appalachian natural gas properties for $3.48bn (£2.31bn) in cash, giving Consol a leading position in the growing Marcellus Shale field.
Consol said it plans to issue $4bn in debt and equity to fund the purchase.
The deal is the latest sign that energy companies are targeting faster development of natural gas resources as the fuel wins an increasing share of the global energy market.
In December, Exxon Mobil said it would buy XTO Energy for about $30bn in stock to expand its natural gas portfolio in North America.
Consol said the purchase would boost its proved reserves of gas by more than 50 per cent to about 3 trillion cubic feet.