Influence of small scale heterogeneity on CO2 trapping processes in deep saline aquifers

TL;DR

This paper explores how small-scale heterogeneity in deep saline aquifers influences CO2 trapping mechanisms, emphasizing the importance of multi-scale geological features for accurate modeling of CO2 sequestration.

Contribution

It introduces a new perspective on the significance of hierarchical small-scale heterogeneity in CO2 trapping processes within deep saline reservoirs.

Findings

Small-scale features critically impact CO2 trapping efficiency.

Hierarchical geological structures influence CO2 plume dynamics.

Understanding heterogeneity improves reservoir performance predictions.

Abstract

The physical mechanism of CO2 trapping in porous media by capillary trapping (pore scale) incorporates a number of related processes, i.e. residual trapping, trapping due to hysteresis of the relative permeability, and trapping due to hysteresis of the capillary pressure. Additionally CO2 may be trapped in heterogeneous media due to difference in capillary pressure entry points for different materials (facies scale). The amount of CO2 trapped by these processes depends upon a complex system of non-linear and hysteretic relationships including how relative permeability and capillary pressure vary with brine and CO2 saturation, and upon the spatial variation in these relationships as caused by geologic heterogeneity. Geological heterogeneities affect the dynamics of CO2 plumes in subsurface environments. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to the performance of some deep saline reservoirs. We investigated how the dynamics of a CO2 plume, during and after injection, is influenced by the hierarchical and multi-scale stratal architecture in such reservoirs. The results strongly suggest that representing small scales features (decimeter to meter), including their organization within a hierarchy of larger-scale features, is critical to understanding trapping processes.