3-D AVO processing and application

Lee, Sheng-Shyong; Wu, Steve Shui Chih; Hsu, Ching-Hsiang; Lin, Jen‐Yang; Yang, Yu-Liang; Huang, Changsheng; Jeng, Lina-De

doi:10.1190/1.1438041

Cited by 3 publications

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“…The theoretical background to AVO is based on the work of Zoeppritz (1919), who derived expressions for the reflection coefficient as a function of angle of incidence, and this method was used by Ostrander (1984), who introduced the variation with offset of reflection coefficients as a direct hydrocarbon indicator. Since then, AVO has been successfully used in different environments including 3D seismic measurements (Castagna 1993; Lee et al 1998).…”

Section: Introductionmentioning

confidence: 99%

AVO investigations of shallow marine sediments

Riedel¹,

Theilen

2001

Geophysical Prospecting

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AVO/AVA (Amplitude Versus Offset/Angle) analysis has been used to determine the physical characteristics o f shallow marine sedi ments. The parameter that can be constrained, are P-and S-wave velocity, bulk density and acoustic attenuation. Shear modulus and other geotechnical properties such as grain size can be inferred from these parameters. The theory o f AVO investigations is given by the Zoeppritz equations (Zoeppritz, 1919), which allow the com putation o f the reflection and transmission coefficients as a function o f angle o f incidence. AVO has been w idely used in the petroleum industry, usually for frequencies o f 20-100 Hz. High frequency shallow sediment AVO studies require special analysis including careful geometry and source and receiver directivity corrections. In the past, marine sediments have been m odeled as elastic materi als. However, viscoelastic models with absorption are more realis tic. At large angle o f incidence, AVA-fimctions derived from vis coelastic models differ significantly from those with purely elastic properties. The influence o f S-wave velocity on the reflection coef ficient is rather small (especially for the low S-wave velocities encountered at the seafloor). On the other hand, P-wave velocity and density show a considerably stronger effect (Fig. 1). Thus, it will be difficult, or nearly impossible, to extract the S-wave param eter from AVA trends, especially when the signal-to-noise ratio is low.In order to measure the reflection coefficient in a seismogram, the peak amplitudes o f the direct wave and the seafloor reflection in a CMP (Common Mid Point) gather are determined and corrected for spherical divergence, and source and receiver directivity (Fig. 2). At CMP locations showing different AVA characteristics, the sedi ment parameters P-and S-wave velocity, density and absorption are determined by using a Sequential Quadratic Programming (SQP) inversion technique. The use o f the viscoelastic model within the inversion gives better results in fitting the data than the elastic model without absorption.The introduction o f constraints, e.g. empirical relationships given by core investigations, can improve and stabilize the inversion results.In Fig. 2, a soft mud layer, with a typical low P-wave velocity close to w ater velocity, forms the seafloor at CM P-Bin 570 whereas at CMP-Bin 4000 the seafloor contains boulder clay, a mixture of sand and gravel with a higher P-wave velocity and density. In both cases the inversion gives reasonable results for the first three sediment parameters. Note that the value o f the S-wave veloc ities have an uncertainty o f more than 100% due to the insensitivi ty o f the reflection coefficient to this parameter.The investigation o f deeper sediment layers by AVA requires a good estimate of the absorption (described by the Q-factor) within the first sediment layer.The influence of Q on the reflection coefficient is enhanced in the wide-angle domain. However, our measurements were restricted to a maximum angle of incidence of 60°, which...

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Section: Introductionmentioning

confidence: 99%

AVO investigations of shallow marine sediments

Riedel¹,

Theilen

2001

Geophysical Prospecting

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Application of 3D AVO interpretation technique to lithological reservoir in the Hongze Area

Zhan-an

2005

Appl. Geophys.

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In the Hongze Area, the reservoirs vary rapidly laterally and are controlled by many factors, such as structure, lithology, oil source, and so on. S-wave well log curves are calculated from an equation derived from multiple-attribute regression analysis of RT, DT, GR, and DEN logs. Representative P-and S-wave velocities and Poisson's ratio are statistically computed for oil and water bearing reservoir rock, shale, and calcareous shale in each well. The averaged values are used for AVO forward modeling. Comparing the modeling results with actual seismic data limit the possible AVO interpretations. Well and seismic data are used to calibrate inverted P-wave, S-wave, Poisson's ratio, and AVO gradient attribute data sets. AVO gradient data is used for lithofacies interpretation, Pwave data is used for acoustic impedance inversion, S-wave data is used for elastic impedance, and Poisson's ratio data is used for detecting oil and gas. The reservoir and hydrocarbon detections are carried out sequentially. We demonstrate that the AVO attributes method can efficiently predict reservoir and hydrocarbon potential.

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2014

Avo

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3-D AVO processing and application

Cited by 3 publications

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AVO investigations of shallow marine sediments

AVO investigations of shallow marine sediments

Application of 3D AVO interpretation technique to lithological reservoir in the Hongze Area

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