Southwestern Energy is putting a lot of energy into gas and oil exploration and production, and midstream activities -- natural gas gathering, transportation, and marketing -- primarily in the Southwest of the US. The company operates in Arkansas, Oklahoma, and Texas, but also in Pennsylvania, and New Brunswick, Canada. In 2015 the oil and gas company reported estimated proved reserves of more than 6.2 trillion cu. ft. of natural gas equivalent, all of which was natural gas. Southwestern's core properties include assets in the Fayetteville Shale play and the Marcellus Shale. SEECO, Inc. and Southwestern Energy Production Company (SEPCO) are the company's primary exploration and production units.