Geology and the Effects on Filling Pattern in CO2 Storage Sites

The filling of a reservoir with CO is a dynamic process influenced by heterogeneities at a range of different scales. If parts of the reservoir are by-passed during this process it will result in lowered filling efficiency and therefore smaller capacity than if assuming homogeneity. This study attempts to illustrate that even small-scale heterogeneity has implications for how the CO is distributed and trapped in sedimentary sequences, and outlines a workflow for the study of these effects. In certain reservoirs the distribution of the injected CO into partly or fully separated layers might mean efficient use of the pore space in the reservoir. However, the mobility may also cause CO to bypass some of the pore space, depending on the heterogeneity and anisotropy of the permeability. After injection has stopped, the heterogeneity will influence the imbibition process when brine displaces the CO, which might cause additional trapping beyond that prescribed by the endpoints for the saturation functions.