Effects Of Fractured Reservoir Elastic Properties On Azimuthal Avo
Name
1997.7 Shen et al.pdf
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557.05 KB
Format
Adobe PDF
Checksum (MD5)
1719f0d1ce3145f08ddf3570341a8389
Author(s)
Shen, Feng
Zhu, Xiang
Toksoz, M. Nafi
Date Issued
1997
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1997-07
Abstract
Aligned vertical fractures introduce velocity anisotropy which is directly related to
parameters, such as fracture density, fracture shape and fracture contents. Effective
medium models allow us to study qP- and qS-wave velocity anisotropy in rocks with
aligned vertical fractures, intersecting fracture sets and aligned fractures with smallscale porosity. Spatially varying fracture density distributions result in velocity spatial variations. Stochastic modeling is used to quantify velocity heterogeneity in a fractured reservoir, where the fracture density field is modeled as a stationary Gaussian random field specified by a covariance function describing the amplitude, orientation, characteristic wavenumbers, and roughness of a fracture density field. The goal of the modeling is to relate the stochastic forward model to the statistics of the velocity and seismic reflectivity fields.
Three-dimensional finite difference modeling has been used to investigate the seismic
response of fractured reservoirs in P-wave seismic data, and the effects of background
Vs/Vp contrasts and anisotropic overburden. The numerical results indicate that background Vs/Vp contrasts across the reflecting boundary, and the presence of anisotropy
above the reservoir, have significant effects on azimuthal AVO response at the top of
fractured reservoirs. Although a larger Vs/Vp contrast gives rise to a strong AVO response in isotropic media, it is not necessary to give rise to a strong azimuth AVO
response. Our numerical modeling shows that the smaller Vs/Vp contrast model gives
rise to a strong azimuthal AVO response. Anisotropic overburden always modifies the
azimuthal AVO response.
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