Fluid saturation effects on dynamic elastic properties of sedimentary rocks. [Laboratory studies; for interpretation of sonic well logs and seismic field data]
The influence of saturation by water, oil, gas, and mixtures of these fluids on the densities, velocities, reflection coefficients, and elastic moduli of consolidated sedimentary rocks was determined in the laboratory by ultrasonic wave propagation methods. Twenty rock samples varying in age from Pliocene to early Devonian and in porosity from 4 to 41 percent were tested under uniform pressures equivalent to subsurface depths of 0 to 18,690 ft. Fluid saturation effects on compressional-wave velocity are much larger in low-porosity than in high-porosity rocks; this correlation is strengthened by elevated pressures but is absent at atmospheric pressure. At a frequency of 1 MHz, the shear-wave velocities do not always decrease when liquid pore saturants are added to rocks as theorized by Biot; agreement with theory is dependent upon pressure, porosity, fluid-mineral chemical interactions, and the presence of microcracks in the cementing material. Experimental results support the belief that lower compressional-wave velocities and higher reflection coefficients are obtained in sedimentary rocks that contain gas. Replacing pore liquids with gas markedly reduces the elastic moduli of rocks, and the effect is enhanced by decreasing pressure. As a rule, the moduli decrease as the porosity increases; Poisson's ratio is an exception to the rule. Liquid and gas saturation in consolidated rocks can also be distinguished by the ratio of compressional and shear wave velocities (V/sub p//V/sub s/). The potential diagnostic value of elastic moduli in seismic exploration may stimulate interest in the use of shear-wave reflection methods in the field.
- Research Organization:
- Univ. of Texas, Austin
- OSTI ID:
- 7332250
- Journal Information:
- Geophysics; (United States), Vol. 41:5; Conference: 45. annual intertional SEG meeting, Denver, Colorado, USA, 16 Oct 1975
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
47 OTHER INSTRUMENTATION
SEDIMENTARY ROCKS
PHYSICAL PROPERTIES
WAVE PROPAGATION
SEISMIC SURVEYS
DATA ANALYSIS
SONIC LOGGING
ELASTICITY
NATURAL GAS
OILS
POISSON RATIO
POROSITY
PRESSURE DEPENDENCE
REFLECTION
SATURATION
SEISMIC WAVES
ULTRASONIC WAVES
VELOCITY
WATER
YOUNG MODULUS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOPHYSICAL SURVEYS
HYDROGEN COMPOUNDS
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
ROCKS
SOUND WAVES
TENSILE PROPERTIES
WELL LOGGING
580201* - Geophysics- Seismology & Tectonics- (1980-1989)
440400 - Well Logging Instrumentation
580203 - Geophysics- Geophysical Survey Methods- (1980-1989)