Analysis of Vertical Permeability and Its Influence on CO2 Enhanced Oil Recovery and Storage in a Carbonate Reservoir

Summary The objective of this study is to improve understanding the geostatistics vertical (bed-normal) permeability (kz) and its influence on reservoir performance during CO2 enhanced oil recovery (EOR) storage. kz scrutinized far less often than horizontal (kx, ky) in most geological modeling. However, our work indicates that it equally important understand characteristics better evaluate their EOR storage prediction. We conducted approximately 9,000 whole-core triaxial ky, kz) measurements from 42 wells a San Andres carbonate reservoir. analyzed data, including heterogeneity, correlation, sample sufficiency measures. with largest smallest fractions points > kmax = max(kx, explore factors coincided large kz. quantified these effects through conditional probabilities potential barriers (e.g., stylolites). Every well had at least some whole cores where kmax. This statistically justifiable result; only Prob(kz kmax) different 1/3 are core samples nonisotropic. In conventional data interpretation, however, modelers usually assume For fraction (11%) >kmax, cumulative distribution functions (CDFs) differ coincide presence stylolites. found twice as variable kx many wells. makes more difficult interpret because was (and is) heavily undersampled. To heterogeneity flow, we built series flow simulation models captured geostatistical permeability, while considering realizations, regimes buoyant flow), injection strategies, heterogeneity. simulations showed that, for viscous assuming similar along constant kz/kx 0.1 yields close (within 0.5%) production case both uncorrelated variables. differs by 10% [at 2.0 hydrocarbon pore volume (HCPV) injected] between two cases. Such flows could occur small rates long times, interwell regions, and/or vertically permeable conduits. Our characterization demonstrates controls how interpretation practices. can help operators refine development programs, particularly reservoirs exists. More broadly, findings potentially apply other subsurface buoyancy-driven displacements, hydrogen storage, geothermal production, aquifer sequestration.