As of December 31, 2012, our Michigan operations comprised approximately 35% of our total estimated proved reserves. As of December 31, 2012, approximatley 89% of our Michigan total estimated proved reserves were natural gas. For the year ended December 31, 2012, our average production was 9.2 MBoe/d or 55.2 MMcfe/d. Estimated proved reserves attributable to our Michigan properties as of December 31, 2012 were 51.7 MMBoe. Our integrated midstream assets enhance the value of our Michigan properties as gas is sold at MichCon prices, and we have no significant reliance on third party transportation. We have interests in 3,677 productive wells in Michigan. Our capital spending in Michigan for the year ended December 31, 2012 was approximately $12 million.
The Antrim Shale underlies a large percentage of our Michigan acreage; wells tend to produce relatively predictable amounts of natural gas in this reservoir. On average, Antrim Shale wells have a proved reserve life of more than 20 years. Since reserve quantities and production levels over a large number of wells are fairly predictable, maximizing per well recoveries and minimizing per unit production costs through a sizeable well-engineered drilling program are the keys to profitable Antrim development. Growth opportunities include infill drilling and recompletions, horizontal drilling and bolt-on acquisitions.
Our non-Antrim interests are located in several reservoirs including the Prairie du Chien (“PdC”), Richfield (“RCFD”), Detroit River Zone III (“DRRV”) and Niagaran (“NGRN”) pinnacle reefs.