Effects of pressure, temperature, and pore water on velocities in Westerly granite

Journal Article · Mon Feb 09 23:00:00 EST 1976 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB081i005p00899· OSTI ID:7175775

Spencer, Jr, J W; Nur, A M

Compressional and shear wave velocities have been measured in Westerly granite under conditions of high temperature to 500/sup 0/C, high confining pressure to 5 kbar, and independently controlled pore water pressure. Measurements in a dry sample show that at a given temperature, confining pressure has a larger accelerating effect on compressional wave velocity (V/sub p/), while at a given confining pressure, temperature has a larger retarding effect on shear wave velocity (V/sub s/). The combined effects of temperature and pressure act to increase Poisson's ratio in a dry rock. Increasing the temperature of a sample that contains pore water at low pressure causes a continuous decrease in the bulk modulus (k) and V/sub p/, while the shear modulus (..mu..) and V/sub s/ are affected only by the temperature of the crystalline matrix. The low V/sub p/ and nearly unchanged V/sub s/ cause a decrease in Poisson's ratio. Under otherwise identical conditions of pressure and temperature, high pore fluid pressure causes a decrease in ..mu.. and V/sub s/, while V/sub p/ is less affected, and Poisson's ratio increases. This trend continues until at high temperatures the bulk modulus of the pore water decreases and results in a decrease in V/sub p/. Gassmann's theory is found to predict closely the compressional and shear wave velocities of saturated porous samples from the elasticity of their dry crystalline matrix and the known properties of water. Finally, time-dependent compressional velocities may be caused in laboratory samples by solution of quartz in supercritical pore water.

• Research Organization: Stanford Univ., CA
• OSTI ID: 7175775
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 81:5; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ACOUSTIC MEASUREMENTS
CHALCOGENIDES
COMPRESSION
FLUIDS
GEOPHYSICAL SURVEYS
GRANITES
HIGH PRESSURE
HIGH TEMPERATURE
IGNEOUS ROCKS
INCLUSIONS
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POROSITY
QUARTZ
ROCKS
SATURATION
SEISMIC SURVEYS
SEISMIC WAVES
SHEAR PROPERTIES
SILICON COMPOUNDS
SILICON OXIDES
TEMPERATURE EFFECTS
VELOCITY