Sanchez Production Partners LLC, formerly Constellation Energy Partners LLC (CEP), is engaged on the acquisition, development and production of onshore oils and natural gas properties in the United States. All of the Company's proved reserves are located in the Black Warrior Basin in Alabama, the Cherokee Basin in Kansas and Oklahoma, the Woodford Shale in the Arkoma Basin in Oklahoma and the Central Kansas Uplift in Kansas and Nebraska. The Company operates its oil and natural gases properties as one business segment: the exploration, development and production of oil and natural gas. As of December 31, 2011, the Company's total estimated proved reserves were approximately 201.3 billions of cubic feet equivalent (Bcfe), approximately 76% of which were classified as proved developed, and 97% of which are natural gas and 3% of which are oil. In March 2013, it announced sale of its Robinson's Bend Field assets, located in Tuscaloosa County, Alabama.