Observations of the Impact of MM-Cm Scale Lamination on the Migration and Trapping of CO <sub>2</sub> in Reservoir Rocks

Abstract

Small scale (mm-cm scale) capillary heterogeneity can result in capillary induced flows and trapping. This can have significant impact on the migration of the injected CO2. In this research, we have measured and characterized the impact of small scale lamination on multiphase-flow parameters and residual trapping of CO2 by combining experimental, numerical, and analytical methods. Experimental CO2/water core-flood tests were performed at reservoir conditions on a laminated reservoir rock core. A medical X-ray CT scanner was used for visualization. Effective drainage and imbibition relative permeability, effective drainage capillary pressure, and residually trapped CO2 were measured. The experimental results were used to obtain a model of the rock core using the method described in. The layers of the rock core are tilted and truncated at the inlet, outlet, and radial outer boundary of the core. To correct for this, the layers were shifted, such that the layers became parallel to the flow direction and extended in the lateral direction. The model of the rock core was used to simulate the drainage core-flood test for a range of flow-rates and flow-rate dependent effective relative permeability and capillary pressure were derived. In addition, simplified analytical models were used to obtain these drainage parameters, as well as capillary limit imbibition effective relative permeability and capillary pressure. The results indicate that simplified analytical models can give a good approximation of these effective multi-phase flow parameters. Furthermore, they show that to correctly derive effective multi-phase flow parameters for layered systems, the geology of the system has to be taken into account. Experimental measurements on rock cores with artificially truncated layers can lead to the incorrect inclusion of the impact small scale heterogeneity.