A Novel Grain-Contact Modelling Approach for Enhanced Petro-Elastic Simulations in Digital Rock Physics Applications

The characterization of structural and stratigraphic trapping of CO2 at a given storage site dependsprimarily on the CO2 migration in the field. With increased focus on migration-assisted CO2 sequestrationin saline aquifers, CO2 solubility, residual CO2 trapping, and process monitoring during CO2 plumemigration are areas of growing research and business interest. CO2 solubility trapping, a primary drainageprocess influenced by pressure, temperature, and brine salinity, leads to pH reduction, and promotes reactivegeochemical processes. Residual CO2 trapping, a secondary process as water re-imbibes storage volumes,is equally critical. Both mechanisms are vital for safe storage and form the foundation for cost-efficientmonitoring and prediction techniques, leveraging pore-scale rock physics experiments, simulations, andfield-upscaling workflows. On the pore scale, computational methods such as pore-network modeling andmorphological methods simulate capillary pressure, relative permeability saturation functions, and reactivetransport to model CO2 trapping functions and their evolution over time. This research advances an efficientmethodology to characterize rock properties across pore-to-log-to-seismic scales, enabling computation ofspecific rock physical properties – especially seismic velocities (Vp and Vs) – for dry, variably saturated,and reactive transport-exposed samples. Enhanced grain mineral configuration identification via a watershedsegmentation method is central to this approach. By modeling stiffness reduction at grain-grain contactzones and adjusting for contact area, grain size, and surface area, the algorithm overcomes typicaloverestimations of effective stiffness in standard µ-CT analysis. The presented software developmentsoptimize the need for laboratory measurements, enabling simulation of mixed water-CO2 saturated storagerocks and their acoustic properties under various conditions. These advancements improve theimplementation of seismic 4D monitoring programs, which are often legally required, by facilitating betteranalysis of physical changes in rock types with time. Furthermore, they enhance understanding ofgeochemical changes in storage rocks through geomechanical-petrophysical properties, contributing to riskreduction and bolstering social acceptance of CCS projects. By digitally performing necessarymeasurements and limiting laboratory work to calibration purposes, the environmental compatibility of CCSstorage development improves. This study demonstrates the workflow using OMV data, and laboratorymeasurements on reference and in-situ rock samples from potential CO2 storage sites.