Rock Strength of Caprock Seal Lithologies: Evidence for Past Seal Failure, Migration of Fluids and the Analysis of the Reservoir Seal Interface in Outcrop and the Subsurface

Scientists have proposed that in order to avoid damaging climate change further accumulations of anthropogenic atmospheric carbon dioxide (CO2) must be limited. One of several proposed techniques for reducing the amount CO2 reaching the atmosphere is carbon capture and storage (CCS). This emerging technology stores CO2 Emissions captured from large point sources (i.e. power plants or industrial facilities), in deep geologic formations, including depleted hydrocarbon reservoirs and saline aquifers. For successful CCS design, implementation and appropriate site selection and subsurface trapping mechanisms must be ensured over the 100\u27s to 1000\u27s of year timescale. A key component in trapping and storage of fluids or gas in the subsurface is caprock seal integrity. This dissertation research focuses on how variations in material properties, rock strength, and stress history of caprock seals affect sealing capacity. Compositional changes in rocks often concentrate near depositional interfaces and discontinuities, such as fractures and fault. these pre-existing structures can act as zones of weakness, which can be reactivated due to the injection and storage of fluids into the subsurface, and can result in increased permeability within the very fine-grained rocks that make up the sealing unit to subsurface fluid or gas. The results of this research show the important role variation in mechanical properties due to lithologic changes have on rock deformation and fracture formation and distribution. Project costs were largely funded by a DOE research grant # DE-FC26-OxNT4 FE 0001786 and DE-SC0004991 to Dr. J. P. Evans. Project costs were associated with travel to and from field sites with field assistants, sample preparation, geochemical and petrographic analysis of samples, as well as teaching assistantships, research assistantships, and a GDL Fellowship appointed to Elizabeth S. Petrie during the course of this research