Impacts of relative permeability hysteresis on the reservoir performance in CO2 storage in the Ordos Basin

The CO2 storage reservoir for the Shenhua Carbon Capture and Storage (SHCCS) Demonstration Project in the Ordos Basin in China is known for its low-permeability and low-porosity characteristics. However, injectivity was shown by the in situ monitoring data to be substantially increasing over the years. Previous numerical analyses suggest that such reservoir behavior might be mainly attributed to the permeability heterogeneity of the injection layers. As an intermittent injection procedure was actually practiced in this project, the hysteretic behaviors in relative permeability and capillary pressure in the reservoir could be significant. In this study, the hysteretic processes are investigated for a better understanding of the reservoir performance. History-match is achieved with one order of magnitude lower in the overall permeability of the principal injection layer than the previous simulation. Current calibrated permeability is much closer to seismic measurement and well-log results. Therefore, we believe that the hysteresis effects accompanying the alternation between injection and injection pause might be another important factor accounting for the observed reservoir performance. It is indicated in this study that, by considering the hysteresis effects in the injection-pause sequence, an optimally-designed intermittent injection procedure could greatly improve the injection performance in a saline aquifer with low permeability and low porosity that may seem unfavorable to CO2 storage. (C) 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.