--> Abstract: Shear Properties of Oil Shales, by Michael L. Batzle, Jyoti Behura, and Ronny Hofmann; #90078 (2008)
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Shear Properties of Oil Shales

Previous HitMichaelNext Hit L. Previous HitBatzleTop1, Jyoti Behura1, and Ronny Hofmann2
1Geophysics, Colorado School of Mines, Golden, CO
2Shell International Exploration and Production, Houston, TX

In-situ recovery from organic-rich shales involves thermal cracking, steamflooding, or other processes involving high temperatures. These processes change the rock physical properties, and shear properties in particular. We have measured, within the seismic band, the complex shear modulus (and thus also the attenuation) of oil shale samples, both rich in organic content as well as for ‘lean’ or low in organic content.

Both the kerogen-rich and the lean shale show a weak dependence of modulus and Q on frequency. Their properties can be effectively considered frequency independent within the seismic band. These shales, however, show a dramatic change in shear-wave velocity and attenuation with temperature. Their shear moduli and Q decrease with melting of the kerogen, but with the subsequent loss of some of the kerogen, both shear moduli and Q increase. The magnitudes of these changes along the direction of the bedding and perpendicular to the bedding direction, which makes velocity anisotropy and attenuation anisotropy potentially valuable attributes. The velocity anisotropy and attenuation anisotropy of the shales can change significantly with temperature, in some cases by more than an order of magnitude. The amount of kerogen content in a shale also influences the velocity and attenuation. The more the organic content, the lower is the shear modulus and the higher is the attenuation.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas