Encana Oil & Gas has agreed to sell a portion of its Piceance natural gas midstream assets in Colorado, US, to a private midstream firm for $590m.

The Piceance basin midstream assets serve Encana’s Mamm Creek, Orchard and South Parachute production in Rifle, Colorado.

The facilities gather and transport 500 million cubic feet of gas per day and include 260 miles of pipeline and 90,000hp of compression facilities.

Encana’s executive vice-president midstream, marketing & fundamentals Renee Zemljak said the firm has entered competitive, long-term gathering and processing fee agreements with top-tier midstream firms on terms that provide cost stability for its ongoing natural gas developments.

The transaction is subject to regulatory approvals and is expected to close in the fourth quarter of 2011.