InterPore2026

4D X-ray particle tracking velocimetry of multiphase flow through rough fractures: quantifying the influence of roughness on flow dynamics

20 May 2026, 15:05

15m

Oral Presentation (MS03) Flow, transport and mechanics in fractured porous media MS03

Speaker

Sojwal Manoorkar (Ghent University)

Description

Geological storage of anthropogenic CO₂ and underground hydrogen energy storage rely not only on transport processes within porous formations, but also critically on the hydraulic behaviour of natural and induced fractures. Leakage through interconnected fracture and fault networks of the caprock remains one of the major risks for long-term containment. Accurate assessment of storage performance therefore requires a mechanistic understanding of multiphase flow physics in natural rough fractures, both within storage formations and overlying caprocks.

Previous studies, including our own, have shown that fracture roughness at the microscale strongly influences multiphase displacement and generally reduces gas relative permeability [1, 2]. Roughness promotes capillary heterogeneity, which has been suggested to lead to formation of non-wetting phase ganglia and disconnected invasion patterns during drainage. However, the exact mechanisms that promote this behavior have not been observed directly, and direct evidence of this is thus still missing. This is a crucial step to understand under which conditions such phenomena may inhibit multiphase flow at larger scale

In this work, we directly quantify the effect of fracture roughness on micrometer-scale flow and velocity fields by comparing multiphase displacement in a smooth-walled fracture and a natural rough fracture. We conduct a series of 4D particle-tracking velocimetry experiments based on state-of-the-art micro-CT imaging on two samples: one smoothed-walled fracture (Belgian Blue limestone) and one retaining natural roughness from Carmel Formation, USA. Samples are saturated with KI-doped brine for X-ray contrast, after which silicon oil seeded with silver-coated hollow glass tracer particles (5-22 μm) is injected. Time-resolved X-ray micro-CT scans are acquired every 30s at 12 μm voxel size, enabling simultaneous visualization of phase distributions and Lagrangian velocity fields, by adapting the imaging methodology outlined in Bultreys et al. 2024 [3].

The smooth fracture exhibits very stable displacement, whereas the rough fracture shows strongly disconnected, fingering invasion with extensive ganglion breakup. The measured velocity fields demonstrate that constrictions associated with heterogeneous aperture distributions control flow organization, producing locally elevated velocities at advancing gas fronts and frequent breakup near narrow throats. This study hence provides direct experimental evidence linking fracture roughness, aperture variability, and disconnected invasion dynamics. By combining time-resolved imaging with particle-tracking velocimetry, we advance the quantitative understanding of roughness-controlled multiphase flow mechanisms that govern injectivity, trapping, and leakage risks in subsurface storage systems.