Battelle researchers presented a new geomechanical study of sub-Knox formations at the Geological Society of America (GSA) Northeastern/North-Central annual meeting in Pittsburgh on March 21. The study, Geomechanical Assessment of Sub-Knox Formations for Safe CO2 Injection Study in the Midwest U.S., examined suitability of the formations for carbon dioxide (CO2) injection and storage.
Recent advances in research on carbon sequestration have raised questions regarding the integrity of subsurface storage reservoirs in terms of interplay among poro-elastic properties, CO2 injection rate and potential subsurface deformation. This study presented the results from integrated rock property characterization and coupled flow-geomechanical simulations for CO2 injection in the Sub-Knox formations at three sites in the Midwest U.S. The main objectives of this work was to investigate the vertical variation of poro-elastic properties to better define the injection unit and understand the fate of CO2 upon long-term injection into the site.
Researchers used various petrophysical and geomechanical measurements from core samples and advanced well logs (such as multi-component sonic, resistivity image, and nuclear magnetic resonance) to analyze porosity, permeability, Young’s modulus, Poisson’s ratio, principal stresses and others. All these parameters were integrated to subdivide the Sub-Knox formations into various geomechanical units, which are comparable to certain flow-zone units. Next, these parameters were chosen as inputs to coupled flow-geomechanical simulations at various rates of CO2 injection to analyze corresponding stress-field response in the reservoir and caprock.
Preliminary results show that the Basal Sandstone Formation may be considered as a favorable reservoir for CO2 injection, where it has combination of suitable geomechanical properties, porosity, permeability and required overburden. The Basal Sandstone Formation consists of seven poro-elastic units, out of which four units have higher rigidity compared to three others. Detailed characterization of sedimentary formations in terms of poro-elastic properties is critical to delineate suitable CO2-injection units for storage and to allow researchers to use these units as a guide for geologically meaningful reservoir simulation.