Exploring residual CO2 trapping in Heletz sandstone using pore‐network modeling and a realistic pore‐space topology obtained from a micro‐CT scan

Geological storage of CO2 in deep saline aquifers mitigates atmospheric emissions. In situ storage is facilitated by several trapping mechanisms including residual trapping, which plays a major role in the containment of CO2. Understanding the underlying mechanisms of residual trapping is crucial for planning storage projects. Of special interest is the relationship between the initial and residual CO2 saturations—the so‐called IR curve, needed for predictive macroscopic‐scale simulations. This study aims to improve the understanding of residual trapping in sandstone from the Heletz site, where extensive field experiments have been performed, by using 3D‐image analysis on core sample CT‐data. This was done to gain knowledge on physical properties (such as radius, coordination number, aspect ratio, shape factor of pores, and pore connectivity) of importance to residual CO2 trapping. Pore‐network flow modeling on a network representation, with the extracted pore‐space topology, was employed to estimate the IR curve. The core sample exhibited pores with a large range of coordination numbers, a mean aspect ratio of 1.4, and shape factors mostly corresponding to triangular cross‐sections. The estimated IR curve was monotonic, fitting an Aissaoui‐type trapping model, displaying a lower sensitivity to the advancing contact angle than previously thought, and indicating a good ability to residually trap CO2. This study provides the first report of values for the three above mentioned properties for Heletz sandstone, and the first estimate of an IR curve for CO2/brine in Heletz sandstone based on pore‐network modeling on a network with a topology retrieved from a core‐sample CT‐scan. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.