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| Prestack inversion of anisotropic coefficients and its application in fracture prediction |
XIE Rui( ), YAN Jian-Guo(), CHEN Qi |
| Geophysical College,Chengdu University of Technology,Chengdu 610059, China |
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Abstract The forward modeling of wave field response characteristics of wide-azimuth seismic data shows that the reflection coefficient has apparent azimuth anisotropy when the P-waves propagate in underground geologic bodies.It has become a research hotspot at home and abroad to make a fracture prediction using azimuth anisotropy.This study analyzed the response characteristics of the changes in seismic P-waves with azimuth using forward modeling.Based on the analytical results combined with the relationship between the anisotropy parameters of fluid-bearing fractures proposed by Bakulin et al.,this study approximately simplified the Ruger formula,deduced the equation between anisotropic parameter γ that can be used to characterize fracture development and reflection coefficient,and proposed a fracture prediction method based on anisotropic parameter inversion.The validity and applicability of the method have been proven using theoretical models and practical data application.Therefore,this study provides a feasible method and technology for fracture prediction using wide-azimuth prestack seismic data.
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Received: 21 August 2021
Published: 17 August 2022
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Corresponding Authors:
YAN Jian-Guo
E-mail: 2429259471@qq.com;yanjianguo@cdut.edu.cn
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Variation of P-wave reflection coefficient with azimuth in isotropic and HTI media models
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Variation of P-wave reflection coefficient of HTI medium model with anisotropic parameters
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| 参数 | vp/(m·s-1) | vs/(m·s-1) | ρ | φ | θ | | Layer 1 | 2000 | 1253 | 2.2 | 45 | 30 | | Layer 2 | 2337 | 1437 | 2.3 | 45 | 30 |
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Variation of P-wave reflection coefficient of HTI medium with anisotropic parameters
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Flow chart of anisotropic coefficient inversion
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| vp/(m·s-1) | vs/(m·s-1) | ρ/(g·cm-3) | ξ | δ | γ | θ | φ | | 4000 | 2300 | 2.8 | 0 | 0 | 0 | 0~60 | 0~180 | | 5500 | 3100 | 2.65 | 0.05 | 0.25 | 0.2 | | |
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According to the data of the study area, the model parameters are established
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Comparison of isotropic calculation results of different equations with incident angle
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Comparison of anisotropic terms of different equations with incident angle(a) and azimuth(b)
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Prestack gathers are synthesized at different azimuth angles at the target layer of the corresponding well in the study area
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Anisotropic parameter curve inversion results theoretical results and inversion results at well BZ-B based on least square method
a—longitudinal wave impedance reflection coefficient;b—transverse wave impedance reflection coefficient;c—anisotropic parameter γ
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Seismic well connection profile in the study area
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AVAZ prestack fracture prediction well connection profile
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Prestack anisotropic parameter inversion fracture prediction well connection profile
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| 数据体编号 | 入射角范围/(°) | 中心入射角/(°) | 方位角范围/(°) | 中心方位角/(°) | | 1 | 10~30 | 15 | 30~60 | 45 | | 2 | 20~30 | 25 | 90~120 | 105 | | 3 | 20~40 | 30 | 120~150 | 135 | | 4 | 30~40 | 35 | 150~180 | 165 |
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Division of incident angle and azimuth selected for actual data inversion
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