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Anisotropic Azimuthal (HTI) Processing
In order to compensate for VTI (Vertical Transverse Isotropy) effect, easily identified in CDP gathers with a behavior commonly known as hockey sticks, anisotropic parameter ETA is identified using semblance analysis.
Once ETA volume is ready, a 4th order NMO (Normal Moveout) correction is applied to the CDP gathers in order to compensate for the VTI effect.
It is known that identifying the fracture pattern of shale plays helps to reduce risk in the drilling process. For that reason an HTI (Horizontal Transverse Isotropy) correction is applied using the workflow shown in the next section.
Image a. shows PSTM gathers sorted by azimuth where the HTI effect can be observed. Image b. shows the same PSTM gathers after the Azimuthal Processing workflow is applied. It can be observed how the gathers are corrected, improving the image and the quality of the gathers to be used in following steps.
- Vermeer, G. J. O., 2012, 3D Seismic Survey Design – Second Edition: Geophysical Reference Series No. 12, Society of Exploration Geophysicists.
- Thomsen, L., 1986, Weak Elastic Anisotropy: Geophysics, 51, 1954-1966.
- Alkhalifah, T., and Tsvankin, I., 1995, Velocity analysis for transversely isotropic media: Geophysics, 60, 1550-1566.
- Sublette, V., Sicking, C., and Treadgold, G., 2008, Estimating HTI in the presence of strong VTI: SEG Las Vegas 2008 Annual Meeting.