MODELING CO2 INJECTION IN THE LAMOTTE FORMATION, SOUTHWEST MISSOURI

The Lamotte formation in Southwest Missouri is being characterized for potential shallow CO₂ sequestration, through a research effort led by City Utilities, Springfield, Missouri. The research effort includes drilling, coring and petrophysical analysis, geomechanical measurements of formation strength, geological description of the setting, geophysical characterization, and laboratory analysis of the formation waters and sequestration geochemistry. This paper details the preliminary reservoir modeling.

A baseline model has been created for CO₂ injection into a closed reservoir unit using published data for the Lamotte sandstone. CMG-GEM 2008.12 software has been employed for modeling of injection rate, injection pressure, residual gas trapping, CO₂ solubility, and mineralization reactions. In the preliminary model, CO₂ is injected for 20 years and the fate of the CO₂ is modeled for the next 100 years.

Preliminary results indicate that CO₂ moves upward and mainly spreads in the upper layers, resulting in a headstand cone shape in the reservoir. The migration distance of CO₂ depends strongly on the reservoir properties, such as size, porosity, permeability and maximum sustainable injection pressure.

The injection model is being used to assess overall storage capacity, maximum sustainable pressure, the type, rate and extent of CO₂ trapping, and to investigate an optimum injection strategy. Work conducted thus far indicates the optimum injection strategy is using a horizontal well. Placement of the horizontal well within the reservoir depends on reservoir heterogeneity. However the exact orientation has only a minor effect on the total CO₂ injected over the time period studied.

This paper provides details regarding injection cases examined, and resulting CO₂ migration and pressure profile for each case. The effect of simultaneous withdrawal, and its effect on injection pressure with time, is also given.