THE OHIO RIVER VALLEY CO2 STORAGE PROJECT: A GEOMECHANICAL ANALYSIS

In this study, we report a geomechanical analysis of possible injection zones and their adjacent formations in order to assess the suitability of this site for long-term storage of anthropogenic CO2. This work is part of the Ohio River Valley CO2 Storage Project, an ongoing characterization of a deep saline aquifer as a potential site for CO2 sequestration. This characterization is largely based on data gathered from a 2802 m vertical well drilled on the site of the Mountaineer Power Plant in New Haven, WV. We determined the orientation and magnitude of the principal stresses using well log data, rock strength tests, and mini-fracture tests to develop a geomechanical model of the location. The study site is in a strike-slip stress regime, such that the vertical stress (Sv) is the intermediate principal stress. The orientation of the maximum horizontal stress is approximately N46°E. We then use the geomechanical model to characterize fractures picked from Formation Micro Imager (FMI) log to determine the distribution and orientation of hydraulically conductive fractures within the injection zones and adjacent layers. Based on this characterization, we assess the fracture-enhanced permeability in the injection zones and the effectiveness of adjacent layers to act as seals against the vertical migration of the injected CO2. We also use the magnitude of the minimum horizontal stress (Shmin) to determine the injection pressures that would result in hydraulic fracturing of the surrounding formations; and we determine the direction of fracture propagation from the orientation of Shmin. Due to the low porosity and permeability in the possible injection zones, it is likely that a combination of horizontal wells and hydraulic fracturing of the injection zones will be necessary to increase injectivity, which would allow for more effective sequestration. Characterizing the state of stress in the injection zones is essential in the optimization of well location and hydraulic fracture propagation. Finally, we will determine the maximum fluid pressures that can be maintained in the formations (i.e., their dynamic capacity) without resulting in frictional failure and leakage through hydraulically active fractures in the overlying caprock.