Experimental Investigations on Flow and Mass Transport in Stressed Rough Fractures

Abstract

The study of flow and transport in rough, fractured media is essential in the development of new energy technologies including enhanced geothermal systems, EGS, and CO2 sequestration. This is a complex problem, mostly due to the number of interacting physical processes in the fractured environment.

In this thesis I introduce a novel pressure-controlled Hele-Shaw cell to investigate different physical processes in rough fractures using 3D-printed rock analogs. This system can measure high-resolution fracture aperture and tracer concentration maps under relevant field stress conditions. Using a series of hydraulic and visual measurements, combined with numerical simulations, I investigate the evolving fracture geometry characteristics, pressure-dependent hydraulic transmissivity, and the nature of mass transport as a function of normal stress.

The experimental results show that as the fracture closes and deforms under increasing normal loading: (1) the contact areas grow in number and size; (2) the flow paths become more focused and tortuous; and (3) the transport dynamics of conservative tracers evolve towards a higher dispersive regime. Moreover, under the applied experimental conditions, I observed excellent agreement between the simulated- and the experimentally measured- hydraulic behavior.