Analogue modeling of non-reactive gas transport through porous media utilizing a microfluidic cell, in the context of He/H2 migration

Helium, like hydrogen, are critical resources essential to the energy transition. Despite different end uses for helium (e.g., coolant for fission and fusion reactors) and hydrogen (e.g., energy – storage, fuel), the two gases share key similarities, while also having some notable differences. It has been established that they have overlapping source mechanisms (e.g., radioactive decay within basement rocks, radiolysis associated with shales, etc.) resulting in the two gases being co-located in a number of exploration wells globally. Likewise, due to a similarity in the kinetic diameters of the molecules although not the reactive nature of them, physical traps that work for hydrogen, should in principle also work for helium. However, transport and trapping of these molecules are affected by a number of competing factors. Therefore, the transport mechanisms and rates at both a basin and pore-scale remain poorly understood.

Here we explore the nature of helium and hydrogen transport within porous media utilizing a microfluidic cell, representative of typical upper-crustal siliciclastics found in the subsurface, in combination with time-lapsed geometrical image analysis. At the pore scale, concentration of both elements (i.e. He, H2) within the pore space are dependent on a number of factors, including (1) the number of ejection pulses from a given source migrating through the same pore space, (2) the rate of arrival from the source, and (3) the impact of local hydrological currents on the pore space.

The laboratory experiments are combined with numerical modeling of multiphase fluid flow in porous media using a continuum approach. These models allow pore-scale observations from the microfluidic experiments to be upscaled, providing insight into the influence of flow rate, injection cyclicity, and permeability heterogeneity on gas migration and plume stability at the reservoir scale.