Ultrasonic velocities and dynamic elastic moduli of Mesaverde rocks
Ultrasonic P-wave and S-wave velocities were measured in Mesaverde sandstones and shales as function of confining pressure to 650 MPa, in six directions concurrently. The samples came from five wells in Colorado and Wyoming. The Mesaverde sandstones are quite isotropic; the shales are transversely isotropic with the direction perpendicular to bedding being the slow direction for wave propagation. The anisotropy of the shale is up to 13% for P-waves and 17% for S-waves. The velocity-pressure behavior of these rocks reveals microscopic structural differences between the sandstones and shales. The sandstones contain microcracks that are closed at moderate pressures (less than 100 MPa). The shales do not have the obvious discontinuity in the pressure/velocity record that can be attributed to the microcrack closing. In situ velocities obtained from the well logs of four of the five wells are compatible with the laboratory determined velocities. Dynamic elastic moduli of the rocks at the overburden pressures (8 to 98 MPa) were calculated from the wave velocities and bulk density. They are greater than the static elastic moduli by 50 to as much as 600%. The dynamic Poisson's ratios are much smaller than the static ones. Some of the calculated dynamic Poisson's ratios have small negative values. 19 references, 25 figures, 5 tables.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6345767
- Report Number(s):
- UCID-20273; ON: DE85004408
- Country of Publication:
- United States
- Language:
- English
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ANISOTROPY
DATA
ELASTICITY
EXPERIMENTAL DATA
INFORMATION
MECHANICAL PROPERTIES
NUMERICAL DATA
PRESSURE DEPENDENCE
RESERVOIR ROCK
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SEISMIC WAVES
SHALES
SOUND WAVES
TENSILE PROPERTIES
ULTRASONIC WAVES
VELOCITY
WAVE PROPAGATION