Southwestern Energy Co. has completed its takeover of GEP Haynesville, fortifying the Houston independent’s natural gas portfolio.

The company in November agreed to pay $1.85 billion for GEP, the third-largest private explorer in the Haynesville and Middle Bossier formations. The transaction boosts Southwestern’s Haynesville scale by 700 MMcf/d, giving it total estimated output of 4.7 Bcfe/d.

The deal, management said, “expands exposure” to the Gulf Coast, where liquefied natural gas export and industrial demand is surging

“The transaction builds further scale in the Haynesville,” management said. GEP “deepens the company’s inventory, improves key financial metrics, including margins, returns and per-share ratios, fortifies Southwestern’s financial strength...