Warren Resources, Inc. is an energy company engaged in the exploration, development and production of domestic onshore crude oil and gas reserves. The Company focuses on the exploration and development of its waterflood oil recovery properties in the Wilmington field within the Los Angeles Basin of California, the Marcellus Shale in northeastern Pennsylvania and its coalbed methane (CBM), natural gas properties located in the Rocky Mountain region. The Company owns an approximate 98.9% undivided working interest in the Wilmington Townlot Unit, located in the Wilmington field within the Los Angeles Basin of California. The Company owns a 100% working interest and an approximate 84.7% net revenue interest in the North Wilmington Unit, located in the Wilmington oil field. It holds an approximate 75% working interest and an approximate 60% net revenue interest in the Marcellus Shale assets.