Effect of Pressure and Stress on Water Transport in Intact and Fractured Gabbro and Granite

Journal Article · Wed Dec 10 04:00:00 EST 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB085iB12p07059· OSTI ID:7064049

Trimmer, D; Bonner, B; Heard, H C; Duba, A

New laboratory data are reported on the effect of confining pressure (to 60 MPa), pore-water pressure (to 30 MPa), and stress difference (to 0.88 of the fracture stress) on permeability of intact and fractured White Lake gneissic granite. Westerly granite, and Creighton gabbro. Permeabilities as low as 10/sup -24/ m/sup 2/ (10/sup -2/ darcy) have been measured using a transient technique. Fracture displacement, electrical conductance, compressional velocity, and pulse amplitude are determined simultaneously. The loads applied to the 0.15-m-diameter by 0.28-m-length test sample are controlled automatically, and most data are taken by microprocessor. Tests on the intact gneissic granite indicated permeabilities of 10/sup -22/ to 10/sup -24/ m/sup 2/ that appeared to be unaffected either by effective pressure or by stress. The granite yielded permeabilities of 4 +- 10/sup -20/ m/sup 2/ that decreased by a factor of 2 as effective pressure increased to 25 MPa and varied by a factor of 2 as stress was increased to 0.5 of the fracture stress. Permeability of the gabbro linearly decreased from 2 x 10/sup -22/ to 8 x 10/sup -24/ m/sup 2/ with effective pressures to 25 MPa. Loading of the gabbro up to 0.88 of the fracture stress increased permeability by a factor of 7. The introduction of a throughgoing fracture increased the apparent permeability by 10/sup 6/ to 10/sup 9/ over the intact values in both granite and gabbro. When compared to the initial value, compressional velocities increased by 5% with pressure to 30 MPa in the gneissic granite. For granite, pressurization from 2 to 25 MPa increased the velocity and pulse amplitude by 5 and 30%, and decreased the conductance by 50%. Velocity, amplitude, and conductance were weakly dependent on pressure in gabbro. The addition of stress decreased velocity and amplitude while increasing conductance markedly on both granite and gabbro.

• Research Organization: Lawrence Livermore National Laboratory, Livermore, California 94550
• OSTI ID: 7064049
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 85:B13; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
COMMINUTION
COMPRESSION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
FAILURES
FRACTURES
FRACTURING
HYDRAULIC FRACTURING
IGNEOUS ROCKS
PERMEABILITY
PHYSICAL PROPERTIES
POROSITY
PRESSURE DEPENDENCE
ROCKS
STRESSES
VERY HIGH PRESSURE