胡自多^1,,
吕庆达^2,3,,,
韩令贺¹,
刘威¹,
黄建平²,
杨继东²,
李振春²
1. 中国石油勘探开发研究院西北分院, 兰州 730020
2. 中国石油大学(华东)地球物理系, 青岛 266555
3. 中国石油化工股份有限公司石油物探技术研究院, 南京 211003

基金项目: 国家重点研发计划项目"面向E级计算的能源勘探高性能应用软件系统与示范"（2017YFB0202905）资助


详细信息

作者简介: 胡自多, 男, 1971年生, 高级工程师, 主要从事波动方程数值模拟与成像方法研究.E-mail:huzd@petrochina.com.cn

通讯作者: 吕庆达, 男, 1995年生, 硕士研究生, 主要从事地震波束成像研究.E-mail:chander_0721@sina.com

中图分类号: P631

收稿日期:2018-09-05
修回日期:2019-01-25
上线日期:2020-02-05

Elastic space-time Gaussian beam method for seismic depth imaging

HU ZiDuo^1,,
Lü QingDa^2,3,,,
HAN LingHe¹,
LIU Wei¹,
HUANG JianPing²,
YANG JiDong²,
LI ZhenChun²
1. Research Institute of Petroleum Exploration and Development-Northwest PetroChina, Lanzhou 730020, China
2. Department of Geophysics China University of Petroleum(East China), Qingdao 266555, China
3. Sinopec Geophysical Research Institute, Nanjing 211103, China


More Information

Corresponding author: Lü QingDa,E-mail:chander_0721@sina.com

MSC: P631

--> Received Date: 05 September 2018
Revised Date: 25 January 2019
Available Online: 05 February 2020


摘要
摘要:随着我国勘探开发难度逐步增大，勘探目标开始向裂缝油气藏、岩性油气藏等复杂探区转移，研究高精度、适应性强的多波多分量深度偏移算法在后续的地震解释、属性分析及储层预测中具有重要意义.针对多波多分量地震数据，本文提出了一种二维弹性波时空域高斯束偏移方法.时空域高斯束沿中心射线传播时能够面向成像目标描述局部波场，且对振幅和频率可调制的Gabor基函数有天然的适应性，因而将基于Gabor分解的子波重构方法应用于震源波场构建，从而得到任意点源函数产生的时空域高斯束波场.该方法由于直接在时间域进行计算，可以避开频率域中出现的假频和边缘截断效应等问题.基于各向同性弹性波动方程的Kirchhoff-Helmholtz积分解，利用矢量时空域高斯束传播算子构建格林函数和格林位移张量，并结合上行射线追踪策略，实现了检波点波场的反向延拓.针对矢量波成像问题，本文借鉴弹性波逆时偏移方法从矢量延拓波场中分离出纯纵波分量和纯横波分量，进而采用修改后的内积成像条件产生具有明确物理意义的PP、PS成像结果，避免了转换波成像的极性反转问题.最后利用简单两层模型和不含盐体构造的部分Sigsbee2a模型的成像结果，并将其与应用近似纵横波成像条件、标量和矢量势成像条件的偏移剖面进行对比，验证了本文方法的正确性和有效性.
关键词: 弹性时空域高斯束/
多分量偏移/
格林函数/
上行射线追踪/
内积成像条件

Abstract:As the difficulty of exploration and development in China gradually increases the exploration target begins to transfer to complex exploration areas such as fractured reservoirs and lithologic reservoirs. And it is of vital significance for subsequent seismic interpretation, seismic attribute analysis, and reservoir prediction to develop a multi-wave, multi-component depth migration algorithm which is highly accurate and strongly robust. In order to process common-shot multi-wave and multi-component seismic data, we develop a 2D elastic imaging method using vector space-time Gaussian beam propagation operators. The space-time Gaussian beam can describe the local wave-field of target-oriented areas over the whole central ray path and naturally adapt to the Gabor basis function which is modulated in terms of amplitude and frequency. Therefore, the source wavelet refactored method based on Gabor decomposition is applied to forward wavefield construction and then we can obtain a space-time Gaussian beam wave-field generated by an arbitrary point source function. This method can avoid problems such as aliasing and edge truncation effects occurring in the frequency domain due to its direct calculation in the time domain. Adhering to the framework of the acoustic space-time Gaussian beam method, we perform the up-going ray tracing from subsurface imaging points to the receiver surface for the construction of the backward wavefield. The P-and S-wave-fields are simultaneously extrapolated based on the Kirchhoff-Helmholtz integral solution of the isotropic elastodynamic equation. The Green's functions and Green's displacement tensors are represented with vector space-time Gaussian beam summation. We separate the extrapolated wavefields into compressional and shear modes using the Helmholtz decomposition, and then implement a modified dot-product imaging. This approach permits to produce clear PP images and avoid polarity reversal problems for PS images. Numerical experiments on a simple two-layer model and a partial Sigsbee2a model without salt structure have verified the accuracy and validity of the proposed method.
Key words:Elastic space-time Gaussian beam/
Multi-component migration/
Green function/
Up-going ray tracing/
Dot-product imaging condition



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