Warren Resources, Inc., an independent energy company, engages in the exploration, development, and production of domestic onshore crude oil and gas reserves. It primarily focuses on the exploration and development of waterflood oil recovery projects in the Wilmington field within the Los Angeles Basin of California; and coalbed methane natural gas properties located in Wyoming. The company also has contiguous acreage position in the Marcellus shale located in Wyoming County, Pennsylvania. As of December 31, 2015, it owned natural gas and oil leasehold interests in approximately 106,335 gross. The company was founded in 1990 and is based in Denver, Colorado. On June 2, 2016, Warren Resources, Inc., along with its five affiliates, filed a voluntary petition for reorganization under Chapter 11 in the US Bankruptcy Court for the Southern District of Texas.