Shear Wave Splitting Analysis to Estimate Fracture Orientation and Frequency Dependent Anisotropy

Shear wave splitting is a well-known method for indication of orientation, radius, and length of fractures in subsurface layers. In this paper, a three component near offset VSP data acquired from a fractured sandstone reservoir in southern part of Iran was used to analyse shear wave splitting and frequency-dependent anisotropy assessment. Polarization angle obtained by performing rotation on radial and transverse components of VSP data was used to determine the direction of polarization of fast shear wave which corresponds to direction of fractures. It was shown that correct implementation of shear wave splitting analysis can be used for determination of fracture direction. During frequency- dependent anisotropy analysis, it was found that the time delays in shear- waves decrease as the frequency increases. It was clearly demonstrated throughout this study that anisotropy may have an inverse relationship with frequency. The analysis presented in this paper complements the studied conducted by other researchers in this field of research

Shear wave velocity prediction using seismic attributes and well log data

Formation’s properties can be estimated indirectly using joint analysis of compressional and shear wave velocities. Shear wave data isnot usually acquired during well logging, which is most likely for costsaving purposes. Even if shear data is available, the logging programs provide only sparsely sampled one-dimensional measurements: this informationis inadequate to estimate reservoir rock properties. Thus, if the shear wave data can be obtained using seismic methods, the results can be used across the field to estimate reservoir properties. The aim of this paper is to use seismic attributes for prediction of shear wave velocity in a field located in southern part of Iran. Independent component analysis(ICA) was used to select the most relevant attributes to shear velocity data. Considering the nonlinear relationship between seismic attributes and shear wave velocity, multi-layer feed forward neural network was used for prediction of shear wave velocity and promising results were presented

Microfacies, sedimentary environment and diagenesis of the upper part of Dalan and Kangan Formations in the Kuh-e Surmeh area, Folded Zagros

The upper part of Dallan and Kangan formations (Permian-Triassic), are located in the Kuh-e Surmeh area in folded Zagros Basin with a thickness of 325 m overlying by Nar evaporite member and underlying by Dashtak Formation. Dominant lithology of these formations are limestone and dolomite. Our purpose in this study is to identify microfacieses, sedimentary environment and diagenetic proceses. To overcome this aim, thin sections petrographic studies, leaded to identify 12 microfacieses related to 4 facieses belt: tidal flat, lagoon, shoal and open marine. The observed microfacies patterns indicate a ramp carbonate platform as depositional environment. Based on petrographic studies, the important diagenetic processes in these formations consist of: micritization, dolomitization, cementation, stilolitization and chemical and physical compactions. Burial diagenesis is dominated diagenetic event. The observed porosities in this section are primary and secondary such as fenestral, vuggy, fracture, moldic, interparticle, intraparticle and channe