A Model To Estimate Carbon Dioxide Injectivity and Storage Capacity for Geological Sequestration in Shale Gas Wells

Recent studies suggest the possibility of CO<inf>2</inf> sequestration in depleted shale gas formations, motivated by large storage capacity estimates in these formations. Questions remain regarding the dynamic response and practicality of injection of large amounts of CO<inf>2</inf> into shale gas wells. A two-component (CO<inf>2</inf> and CH<inf>4</inf>) model of gas flow in a shale gas formation including adsorption effects provides the basis to investigate the dynamics of CO<inf>2</inf> injection. History-matching of gas production data allows for formation parameter estimation. Application to three shale gas-producing regions shows that CO<inf>2</inf> can only be injected at low rates into individual wells and that individual well capacity is relatively small, despite significant capacity variation between shale plays. The estimated total capacity of an average Marcellus Shale well in Pennsylvania is 0.5 million metric tonnes (Mt) of CO<inf>2</inf>, compared with 0.15 Mt in an average Barnett Shale well. Applying the individual well estimates to the total number of existing and permitted planned wells (as of March, 2015) in each play yields a current estimated capacity of 7200-9600 Mt in the Marcellus Shale in Pennsylvania and 2100-3100 Mt in the Barnett Shale.