Penn West Petroleum Ltd. (Penn West) is a Canada-based senior exploration and production company. The Company operates to explore for, develop and hold interests in oil and natural gas properties and related production infrastructure in the Western Canada sedimentary basin directly and through investments in securities of subsidiaries holding such interests. The Company's portfolio of properties includes both unitized and non-unitized oil and natural gas production. The properties contain long-life, low-decline-rate reserves and include interests in several oil and gas fields. The majority of its proved plus probable reserves are located in Canada in Alberta, British Columbia, Saskatchewan, Manitoba and the Northwest Territories. It also has minor proved plus probable reserves interests in the United States in Wyoming. Penn West operates under the trade names of Penn West and Penn West Exploration.