Warren Resources, Inc. (Warren) is an independent energy company engaged in the exploration, development and production of domestic onshore crude oil and gas reserves. The Company focuses primarily on the exploration and development of its waterflood oil recovery properties in the Wilmington field within the Los Angeles Basin of California, and its coalbed methane (CBM) natural gas properties located in the Rocky Mountain region. The Company's properties are primarily located in California, Wyoming, New Mexico, North Dakota and Texas. As of December 31, 2012, it owned natural gas and oil leasehold interests in approximately 124,587 gross (94,140 net) acres, approximately 85% of which are undeveloped. On October 9, 2012 (effective August 1, 2012), the Company acquired certain additional natural gas and midstream assets from subsidiaries of Anadarko Petroleum Corporation (Anadarko) in the Atlantic Rim Project in the Washakie Basin.