SPE 139034 Characterization and Simulation of ECBM: History Matching of Forecasting CO2 Sequestration in Marshal County, West Virginia

Uncertainties of CO2 injection-sequestration in a CBM is driven by the complex process of gas desorptioncontrolled mechanism attributed to the natural characteristics of CBM and to the impact of the wells engaged in the reservoir. This work presents the reservoir characterization and simulation process focused on natural gas production and subsequent CO2 injection into an unmineable coal seam in the Marshall Country West Virginia. Two coal seams (Pittsburgh and Upper Freeport) are the subject of this pilot CO2 sequestration project. Methane is produced from both coal seams; however CO2 is injected only in the Upper Freeport which includes four wells. The shallower Pittsburgh coal is used to observe and detect any possible leakage. The objective is to build a reservoir simulation model that is capable of matching the methane production history and forecast field potential capacity for CO2 injection and sequestration. Although injection has taken place in two reasonably close wells, these wells exhibit different production and injection behavior. A commercial simulator is used for modeling. Three realizations of the reservoir were built and history matched base on different Langmuir isotherms. The model which leads to a better approximation of the actual injection profile is selected for further analysis. Upper Freeport formation characteristics, its CO2 storage capacity and CO2 distribution in the reservoir are presented in this article. The model can be used to define safety margins for the maximum bottom-hole pressure during injection. Introduction Sustain economic growth by providing sufficient energy and controlling the CO2 emissions as byproduct of producing Energy from fossil fuels is one of the most challenging tasks for engineers. The dilemma of burning hydrocarbons to produce energy or to stop producing energy from burning the fossil fuels to avoid environmental harm can be solved by sequestering the CO2 emissions into the ground. CBM formations besides producing CH4, they have the capacity of storing CO2 because of the absorptive properties of coal. The process of injecting CO2 and sequester it not only helps to reduce green house effect it also helps the improvement of gas recovery. The process of estimulating the CBM by injecting CO2 to produce more CH4 is called enhanced coalbed methane or