Fracturing in low-permeability soils for remediation of contaminated ground

This paper presents a field study on hydraulic fracturing for in situ remediation of contaminated ground. Sand-propped hydraulic fractures were placed from vertical and horizontal wells at a test facility. Field excavations were conducted to expose the fractures and inspect their distribution and geometry. Fractures that were mapped by field excavation were found to be near horizontal, implying that the soil formation is overconsolidated. It was also observed that the sand "proppant" was thicker at locations where the soil layers were relatively weak or contained weak fissures. Electrical resistivity tomography (ERT) was also conducted in an attempt to map the fractures. There was no indication that fractures were being mapped by this geophysical technique. Fracture mapping based on tiltmeter data analyses conformed closely with the actual fracture placement in the vertical well but did not properly predict the actual fracture placement in the horizontal well.Key words: hydraulic fracturing, field test, low-permeability soil, electrical resistivity tomography, tiltmeters, horizontal well, vertical well.