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Orthorhombic Extension to HTI Velocity Analysis - Theory and Application to a High Density AquisitionNormal access

Authors: C.M. Davison, M.J. Grimshaw, E.M. Murray, M. Kowalczyk-Kedzierska, S. Angio and A. Ourabah
Event name: 76th EAGE Conference and Exhibition 2014
Session: Anisotropic Parameter Estimation - Theory
Publication date: 16 June 2014
DOI: 10.3997/2214-4609.20140781
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.65Mb )
Price: € 20

Summary:
Azimuthal velocity models are now widely used for land seismic exploration. In particular, Horizontal Transverse Isotropy (HTI) models have often been applied as the anisotropic velocity model of choice, to extract velocity information from situations where the earth consists of horizontally fractured media. The velocities extracted can be used both to perform azimuthally dependent move-out to flatten the CMP gathers, providing a sharper and clearer stack, and also to generate the interval velocity models via generalized Dix inversion, which are a powerful tool for interpreters when dealing with fractured earth models. However, HTI velocity models are known to be insufficient as a modelling tool in certain circumstances, particularly in surveys where large offsets are present, resulting in incidence angles of over 30 degrees where higher order terms in the move-out equation start to become significant. This study therefore implements an orthorhombic velocity model as an extension to the standard HTI model, where azimuthally dependent higher order move-out is present in the move-out equation. The method of solution of the orthorhombic model is described, together with an application to a Full-Azimuth high density Independent Simultaneous Shooting (ISSĀ®) survey as an illustration.


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