HR: 1330h
AN: H42F-1131    [PDF]
TI: Experiments on Hydraulic Fracturing in Weakly Cemented Sediments
AU: * Dijk, P E
EM: peter.dijk@ce.gatech.edu
AF: Georgia Institute of Technology, School of Civil and Environmental Engineering, Atlanta, GA 30332-0355 United States
AU: Chang, H
EM: gtg004k@prism.gatech.edu
AF: Georgia Institute of Technology, School of Civil and Environmental Engineering, Atlanta, GA 30332-0355 United States
AU: Germanovich, L N
EM: leonid@ce.gatech.edu
AF: Georgia Institute of Technology, School of Civil and Environmental Engineering, Atlanta, GA 30332-0355 United States
AU: Santamarina, J C
EM: carlos@ce.gatech.edu
AF: Georgia Institute of Technology, School of Civil and Environmental Engineering, Atlanta, GA 30332-0355 United States
AB: Hydraulic fracturing in weakly cemented sediments was studied in the laboratory. Viscous liquids were injected into dry sediments at a constant flow rate while the injection pressure was monitored. The injected liquid solidified after the experiment, and was extracted from the particulate sample. The liquid flow appears to be localized in thin conduits. Often, these channels resemble cracks; by analogy we call them hydraulic fractures. Also, non-fracture phenomena (e.g. cavity expansion, leak off) occur under certain conditions. Different transition stages (i.e., from bulb to thin fracture) can exist. The appearance of the fractures depends on (i) the density, (ii) the particle size distribution and (iii) the stress state (both stress ratio and magnitude) of the particulate materials, and (iv) the viscosity and (v) the flow rate of the injection fluid. The properties of the particulate media (i to iii) and the injection liquid (iv to v) affect the shape and thickness of the fractures. In contrast, the initial stress ratio in the sediment (iii) controls the orientation of the fractures. The injection pressure is affected by all five parameters. Since all the tested materials exhibit strain-softening behaviour, the obtained results suggest that the mechanism of fracture propagation may be due to localized shear bands originating from the fracture tip. The slip of the shear band sides is inclined with respect to the main fracture plane. This results in the normal (mode I) fracture opening, which creates space for continued fluid flow at the fracture tip during its propagation.
UR: http://www.ce.gatech.edu/~leonid/rockmechgroup/research.html
DE: 1719 Hydrology
DE: 5104 Fracture and flow
SC: Hydrology [H]
MN: 2003 Fall Meeting