Aethon III, a unit of Dallas private investment firm Aethon Energy Management LLC, agreed to buy Haynesville-Cotton Valley natural gas assets from QEP Resources Inc. of Denver.

QEP Pres. and Chief Executive Officer Chuck Stanley said the pending $735-million sale is “an important next step in our process of becoming a Permian pure-play company.”

Proceeds will finance development of QEP’s core Permian assets and reduce debt. The transaction includes producing properties, undeveloped acreage, and associated gas gathering and treating systems.