Warren Resources is engaged in the exploration, development and production of domestic onshore crude oil and gas reserves. Co. focuses 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 natural gas properties located in the Rocky Mountain region. Co.'s drilling, completion, production, re-entry and land operations are conducted, managed and supervised through Warren E&P, Inc., its wholly owned subsidiary. As of Dec 31 2014, Co. had estimated net proved reserves of 71.3 million barrels of oil equivalent.