Abstract
Numerical simulators are essential tools to develop a better understanding of the geologic characteristics of brine reservoirs and to build support for future CO2 storage projects. Modeling CO2 injection requires the implementation of multiphase flow and an equation of state to compute the dissolution of CO2 in brine and vice versa. Capillary pressure and relative permeability need to be consistent with permeability/porosity variations. It is, therefore, crucial to gain confidence in the results of numerical simulators by validating the models and numerical accuracies using lab and field pilot scale results. A published steady state core scale CO2/brine displacement results was selected for our numerical study. The experimental results accompanied by fluid properties, relative permeability and capillary pressure curves, and medical X-ray CT images of subcore porosity, CO2 saturation CT images, and gas saturation histogram. Published saturation measurements provided insight into the role of heterogeneity in final CO2 distribution where slight variation in porosity gives rise to large variation in CO2 saturation distribution.
High resolution compositional simulations of brine displacement with supercritical CO2 are presented using IPARS (parallel compositional reservoir simulator). 3D numerical model of the Berea core was constructed using geostatistical based permeability and porosity distributions. Grid cells were on the order of 1 mm x 1 mm x 6 mm with a total of 32000 cells. The core was initially saturated with brine before the injection of supercritical CO2.Fluid properties were calibrated against the measured data. Capillary pressure and relative permeability curves were based on the measurement with capillary pressure scaling based on Leverett J-function for permeability, porosity, and interfacial tension for every grid element. Simulation results indicated that accurate representation of capillary pressure at small scales was critical. Water drying and the shift in relative permeability had significant impact on final CO2 distribution along the core.