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Laboratory hydraulic fracturing experiments in intact and pre-fractured rock

January 1, 1977

Laboratory hydraulic fracturing experiments were conducted to investigate two factors which could influence the use of the hydrofrac technique for in-situ stress determinations; the possible dependence of the breakdown pressure upon the rate of borehole pressurization, and the influence of pre-existing cracks on the orientation of generated fractures. The experiments have shown that while the rate of borehole pressurization has a marked effect on breakdown pressures, the pressure at which hydraulic fractures initiate (and thus tensile strength) is independent of the rate of borehole pressurization when the effect of fluid penetration is negligible. Thus, the experiments indicate that use of breakdown pressures rather than fracture initiation pressures may lead to an erroneous estimate of tectonic stresses. A conceptual model is proposed to explain anomalously high breakdown pressures observed when fracturing with high viscosity fluids. In this model, initial fracture propagation is presumed to be stable due to large differences between the borehole pressure and that within the fracture. In samples which contained pre-existing fractures which were 'leaky' to water, we found it possible to generate hydraulic fractures oriented parallel to the direction of maximum compression if high viscosity drilling mud was used as the fracturing fluid. ?? 1977.

Publication Year 1977
Title Laboratory hydraulic fracturing experiments in intact and pre-fractured rock
DOI 10.1016/0148-9062(77)90196-6
Authors M.D. Zoback, F. Rummel, R. Jung, C.B. Raleigh
Publication Type Article
Publication Subtype Journal Article
Series Title International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts
Index ID 70011115
Record Source USGS Publications Warehouse