Major U.S. pipeline operator Energy Transfer LP said Wednesday it would pay $2.6 billion in an all-stock deal to acquire Enable Midstream Partners LP. Including debt, the transaction is valued at $7.2 billion.

Energy Transfer, whose plan to expand the controversial Dakota Access crude oil pipeline has been met with repeated court challenges and setbacks, would pick up natural gas gathering and processing assets across parts of Oklahoma, Arkansas, Texas and Louisiana, while also combining Enable’s assets with its own existing gas operations on the U.S. Gulf Coast.

The deal is a bid to bolster its natural gas transportation operations and offset the legal and political woes that threaten to imperil the Dakota Access Pipeline. The Standing Rock Sioux Tribe, the Cheyenne River...