Characterization and Quantification of Pneumatic Fracturing Effects at a Clay Till Site
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Environmental fracturing offers assistance to remediation efforts at contaminated, low-permeability sites via creation of active fracture networks, and hence, reduction of mass transport limitations set by diffusion in low-permeability matrices. A pilot study of pneumatic fracturing, focusing on direct documentation of fracture propagation patterns and spacing, was performed at a typical basal clay till site. The study applied a novel package of documentation methods, including injection of five tracers with different characteristics (bromide, uvitex, fluorescein, rhodamine WT, and brilliant blue), subsequent tracer-filled fracture documentation via direct and indirect methods, and geological characterization of the fractured site. The direct documentation methods consisted of Geoprobe coring, augering, and excavation. A mass balance and conceptual model have been established for the distribution of the injected tracers in the subsurface. They reveal that tracer was distributed within 2 m of the fracturing well, mainly in existing fractures above the redox boundary (2 to 4 m.b.s.; 5 to 10 cm spacing). Spacing of observed tracer-filled fractures was large (>1 m) at greater depths. The number of fractures induced/activated could possibly be increased via adjustments to the fracturing equipment design.
Christiansen, C. M., Riis, C., Christensen, S. B., Broholm, M. M., Christensen, A. G., Klint, K. E. S., Wood, J. S. A., Bauer-Gottwein, P., & Bjerg, P. L. (2008). Characterization and Quantification of Pneumatic Fracturing Effects at a Clay Till Site. Environmental Science & Technology (Washington), 42(2), 570-576. https://doi.org/10.1021/es071294s