Ray Tracing and Illumination Ray tracing and illumination tools to validate complex velocity models Ray Tracing and Illumination (RTI) enables interactive illumination studies through velocity models using advanced ray tracing in both isotropic and anisotropic (VTI and TTI) models. The combination of interactive ray tracing and illumination studies gives interpreters and geophysicists the ability to interrogate and validate complex velocity models for imaging and acquisition-related issues. Complex ray signatures involving reflections, transmissions, and wave-type conversions can be specified. Features ■■ ■■ ■■ ■■ ■■ ■■ ■■ Ray shooting—Shoot a single ray, a fan of rays, or a cone of rays from any defined source locations in any direction. The shooting direction can be specified according to source point, suitable for normal incidence ray-tracing of a target horizon, for example. Two-point ray tracing—Find rays shot between source and receiver points. This is the classic application used for simulating surface and downhole acquisition geometries. Rays can be selected as first arrival, maximum energy, or shortest path. Two-point checkshot ray tracing for model validation. Offset ray—Find a pair of specular rays satisfying a required relative surface offset and azimuth of the two ray endpoints. This is an extension to normal incidence ray tracing, and the method used in common image point tomography. Checkshot model validation—Test whether the Volcan velocity model is in agreement with observed checkshot data. This is achieved by comparing direct P-wave ray-traced travel times with the observed times. Illumination spectrum—Use for a target analysis point to determine the range of target dips and azimuths that can be illuminated for a given narrow azimuth (NAZ) or wide azimuth (WAZ) acquisition geometry. This allows the user to assess whether coherent energy observed in the seismic data is potentially primary reflected energy, or indicates the range of dips and azimuths that cannot be illuminated, excluding them as viable candidates for interpretation. Fold of coverage analysis—Create binned hit count and attribute (minimum offset, for example) maps of midpoints and ray reflection points. Allows offset and azimuth binning in addition to standard spatial binning, creating a series of maps that can be displayed individually or in any summed combination. Basic acquisition geometry modeling—Enable the creation of pointsets for basic geometry constructs (points, lines, grids, circles, spirals, and well trajectories), the import of P190 and DIO files, and the replication of pointsets based on a seed pointset. Ray tracing through a velocity model. Prerequisites Petrel* 2012 WesternGeco Seismic Velocity Modeling Plug-in for Petrel For more information, please contact [email protected]. Applications ■■ ■■ ■■ ■■ Provision of essential imaging information for target zones for improved understanding of complex geologic areas Generation of survey designs to achieve required illumination of target zones within a velocity model Model validation using checkshot information by comparing with measured data Migration aperture validation and other seismic processing parameter analysis by relating surface acquisition to imaging points within the model *Mark of Schlumberger Copyright © 2012 Schlumberger. All rights reserved. 12-WGS-0019 www.slb.com/westerngeco