Our US natural gas production is primarily from our Marcellus shale gas interests. The Marcellus shale gas play is the largest unconventional natural gas play in North America, according to a 2009 report prepared by the U.S. Department of Energy. The Marcellus shale gas play covers an area of approximately 95,000 square miles over six states in the northeastern United States. With its proximity to the large northeast US natural gas market and expanding pipeline take-away capacity, Marcellus gas receives a premium price and has one of the lowest breakeven production costs in North America. Natural gas in the Marcellus is accessed through the application of horizontal drilling technology and multi-stage hydraulic fracturing.
To learn more about hydraulic fracturing safety, please read this study by the Energy Institute at the University of Texas
We have an interest in approximately 96,000 net acres of land in the Marcellus. Approximately 44,000 net acres are non-operated and are located in northeastern Pennsylvania where we are partnered with two experienced shale players – EXCO Resources Inc. and Chief Oil and Gas. This region has some of the best prospectivity for natural gas across the entire play. Our operated interests at December 31, 2012 include approximately 52,000 net acres located in central Pennsylvania, West Virginia and Maryland. Our operated acreage in West Virginia and Maryland is expected to be reduced by 26,000 net acres as we have no plans to further develop these leases which are set to expire in 2013.
Our US natural gas produciton in 2012 averaged 53.4 MMcf/day, representing approximately 21% of our total natural gas production. The majority of the production was from non-operated leases in Bradford, Lycoming, Sullivan and Susquehanna counties in Pennsylvania. Our US natural gas proved plus probable reserves were 296 Bcf, or 14% of our total proved plus probable reserves as at December 31, 2012, an increase of 45% from 2011.
We plan to spend approximately $80 million on non-operated drilling projects in our Marcellus properties in the northeast region of Pennsylvania in 2013. This drilling program is expected to result in the majority of our core non-operated acreage to be held by production by the end of 2013. Our Marcellus production is expected to grow to close to 75 MMcf/day exiting 2013, which would represent approximately 30% of our anticipated natural gas production.
We have approximately 1.3 trillion cubic feet of best estimate contingent resources associated with our acreage position in the Marcellus at December 31, 2012.