Warren Resources is a company engaged in the acquisition, exploration, development, and production of domestic onshore crude oil and gas reserves. The company focusses its efforts primarily on the development of its waterflood oil recovery properties in the Wilmington field within the Los Angeles Basin of California, its position in the Marcellus Shale in northeastern Pennsylvania and its coalbed methane, or CBM, natural gas properties located in the Washakie Basin in southwestern Wyoming.