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Anisotropic elastic moduli of carbonates and evaporites from the Weyburn‐Midale reservoir and seal rocks
Author(s) -
Martínez Jaime Meléndez,
Schmitt Douglas R.
Publication year - 2013
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12032
Subject(s) - anisotropy , geology , isotropy , evaporite , transverse isotropy , sedimentary rock , elastic modulus , mineralogy , overburden pressure , geophysics , geotechnical engineering , materials science , geochemistry , optics , physics , composite material
Assuming Vertical Transverse Isotropy (VTI) symmetry the elastic anisotropy as a function of confining pressure of four carbonates and one evaporite from the Williston sedimentary basin in Saskatchewan, Canada is investigated using the ultrasonic pulse transmission method. Ultrasonic P‐ and S‐ wave velocities are obtained from cylindrical plugs cut from a main sample along horizontal, vertical and 45° orientations with respect to the sample's presumed vertical axis of symmetry. The elastic constants were then calculated from the measured velocities and densities. Anisotropy was quantified by estimating Thomsen parameters (Thomsen 1986) from elastic constants. The results show that the samples are at the best weakly anisotropic. The presence of microcracks and pores as well as the heterogeneity of the samples play an important role in defining the P‐ and S‐ wave velocities. The weak anisotropy found in these samples suggests that ‘intrinsic’ properties of these rocks negligibly contribute to the anisotropy observed at the seismic scale.