基于Born/Rytov近似的联合叠前深度偏移方法

The prestack depth migration method based on Born/Rytov approximations

1. 中国科学院研究生院,北京100039;2. 石油大学地球资源与信息学院,山东东营257061

1. Graduate Institute, Chinese Academy of Sciences, Beijing 100039, China;2. College of Earth Resources and Information, University of Petroleum, Dongying 257061, China

波动方程法叠前深度偏移是实现复杂构造和岩性精确成像以及保幅处理的关键技术之一。目前常用的这类方法有分步傅里叶法 (SSF)、傅里叶有限差分法 (FFD)、频率空间域有限差分法 (FXFD)和广义屏法(GS)。其中, GS法是近几年发展起来的一种新方法, 具有成像精度较高、计算效率一般和条件稳定的特点。依据GS法, 考虑到效率、效果和稳定性, 提出了基于Born/Rytov近似的联合叠前深度偏移方法。当延拓层的速度横向变化较小时, 采用Born近似法; 当延拓层的速度横向变化较大时, 采用Rytov近似法。

Wave equation prestack depth migration is one of the key techniques to accurate imaging of complex structures as well as lithologies and preservation of amplitude information. The commonly used migration methods include split step Fourier (SSF), Fourier finite difference (FFD), frequency space domain finite difference (FXFD), and generalized screen (GS). GS is a new method developed in recent years, which is of high imaging precision, average computing efficiency, and conditional stability. In accordance with GS and taking into account the efficiency, accuracy, and stability, we put forward a prestack depth migration method based on Born/Rytov approximations. When the lateral velocity variation of the continuation layer is small, Born approximation was used, otherwise Rytov approximation was used. Tests on Marmousi model and real data proved the effectiveness and adaptability of this method to complex geological bodies.