Séminaire de Matthew Becker (California State University)



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Le jeudi 11 juin 2015 à 11:00, en salle de conf de l'OSUR (campus de Beaulieu, bât.

Le jeudi 11 juin 2015 à 11:00, en salle de conf de l'OSUR (campus de Beaulieu, bât. 14B, RDC), Matthew Becker propose un séminaire intitulé

Confirmation of Hydraulic, Tracer, and Heat Transfer Characterization of a Fractured Bedrock using Ground Penetrating Radar

Présentation :
Over the past five years multiple characterization techniques have been applied to an experimental field site to elucidate flow channeling in bedrock and its influence on contaminant transport and geothermal heat transfer. The field site consists of a 10 x 10 meter five-spot borehole pattern isolated in a single bedding plane fracture in sandstone. The Altona Flat Rock site was developed as a unique field laboratory for testing characterization methods applicable to flow and transport in fractures. The Potsdam Sandstone is exposed at this locale, allowing access to shallow groundwater in bedding plane fractures. Periodic hydraulic tests have shown evidence of preferential flow connections among the wells. This connection was confirmed with multiple ionic tracers which showed different sweep efficiency among well pairs. Heated water tracer studies demonstrated that heat exchange was more efficient in the wells that exhibited greater sweep between well pairs. Finally, surface ground penetrating radar (GPR) was used to map flow in the plane of the fracture by using saline solution to trace flow paths. The implications of the GPR imaging is the focus of this contribution. Reflected radar energy showed a marked change in both amplitude and phase in the presence of saline tracer, allowing flow paths to be imaged. The path followed by the saline tracer was highly anisotropic, presumably following aperture fabrics related to the sandstone depositional environment. Fluid flow, solute migration, and heat transport are all strongly influenced by this anisotropy. These findings highlight the importance of characterizing hydraulic connectivity to predict engineered circulation systems for groundwater remediation, enhanced oil recovery, and geothermal heat extraction. .

Contact :
Matthew Becker (California State University)

Contact OSUR :
Olivier Bour (Géosciences Rennes)