Doctor of Philosophy

dissertationSupercritical carbon dioxide is injected into underground formations to enhance oil recovery and for subsurface sequestration to minimize the impact of CO2 emissions due to global warming. The complex phase behavior of CO2 with oil determines the effectiveness of the CO2 injection for enhanced oil recovery. The injection of CO2 into the subsurface is also affected by the large and small scale heterogeneities in the formations. These two aspects of CO2 injection are examined in this research. Development of multiple-contact miscibility is important in the success of a carbon dioxide enhanced oil recovery. CO2 displacements are often designed to operate above the minimum miscibility pressure (MMP) to ensure the development of multiple contact miscibility between the oil and CO2. Compositional histories in different parts of a two-dimensional domain are examined in this study in relation to displacement pressure employed. The second part of this dissertation deals with the effect of faults on the CO2 sequestration process and on the integrity of storage. Outcrop-based studies of faulted, aeolian Navajo sandstone provide detailed, quantitative insight regarding the range of fault characteristics that might be encountered as injected CO2 migrates through the faulted aquifer. Faults can act as barriers, conduits, or integrated barrier-conduit systems. Uncertainty in knowing whether a subsurface fault will act as a barrier or conduit leads to uncertainty in evaluating the likelihood for economically sequestering CO2 in sandstone aquifers. EclipseR black oil reservoir simulator is used to explore how different, 3-D, fault-related permeability/porosity structures might impact CO2 injection into, migration through, and leakage from a sequestration aquifer. Sandstone permeability values range from 10s to 1000s of mD. Simulator output shows how fault conduits and barriers can restrict migration of CO2 through the aquifer as a consequence of bypassing (conduits) or compartmentalization (barriers). In addition, the simulation results reveal how the geoscientists' ability to quantify and discriminate between high-permeability versus low-permeability faults in sandstone aquifers can play an important role in designing CO2 sequestration operations