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Seismic Critical Reflection Analysis - Constraining Thomsen Anisotropy Parameters in the τ-p DomainNormal access

Authors: M.A.A.M. Jelani, D.A. Angus and A.D. Booth
Event name: 79th EAGE Conference and Exhibition 2017
Session: Seismic Anisotropy in Fractured Reservoirs - The Anisotropic Signatures
Publication date: 12 June 2017
DOI: 10.3997/2214-4609.201701405
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 3.34Mb )
Price: € 20

Summary:
The evaluation of anisotropy parameters is demonstrated in the τ-p (intercept time – horizontal slowness) domain, using pre-stack seismic data. It allows critical slowness, of reflected energy to be identified, from which anisotropic parameters in a target layer can be extracted. However, geometric effects (e.g., horizon dip) can damage the accurate evaluation of the critical slowness, thereby impeding the accuracy of the anisotropy parameters. We simulate pre-stack seismic data from a basin province, featuring “seaward dipping reflector” (SDR) geometries. SDRS are formed by stacked volcanic layers; given the strong velocity contrast between volcanic and host rock, a strongly anisotropic fabric can be introduced. Our simulation delivers synthetic responses through an SDR package, with data in both shot and common-midpoint (CMP) domain supplied to the τ-p transform, include varying anisotropic strengths and dip angle of the uppermost SDR interface. Thus, we consider the accuracy of recovered anisotropy estimates. Our results show that models with similar induced anisotropic fabric but varying interface of uppermost SDR yield different critical slowness and hence, affecting the accuracy of extracting anisotropic parameter values. We propose that anisotropic parameters can be successfully recovered from pre-stack CMP data in the τ-p domain, with accuracy typically better than ±10%.


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