Understanding flow through physical heterogeneities in the subsurface and particularly how heterogeneities lead to preferential flow is useful in diverse fields such as enhanced oil recovery, radioactive waste treatment and groundwater contaminant migration. Fractures are a principal factor controlling both the amount of gas that can be stored in shale and the risk associated with that storage. Sequestering CO2 in shale depends on the diffusion of CO2 into stagnant areas adjacent to the fractures into which the CO2 is injected. In the paper, silicon nano-particles with fluorescent polymer corona were prepared and dispersed in a supercritical CO2 fluid analogue. Together with an inert chemical tracer trifluorotoluene (TFT), they passed through a stainless cylindrical column with a central channel of large diameter sands surrounded by an annulus filled with smaller diameter ones. The chemical tracer showed a longer transit through the system to diffuse into the matrix than the nano-particle tracers. So the nanoparticle tracer arrived first and the chemical tracer later, and the separation measures the degree of preferential flow.

Nanoparticle tracers for measurement of degree of preferential flow in shale

249th National Meeting (2015)

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