一般TI介质中多震相旅行时层析成像——以井间成像为例

传统的各向异性介质中的正、反演研究大多基于弱各向异性假设下的VTI介质,且主要是有关初至波的射线追踪和相应的旅行时反演。然而,随着勘探精度要求的不断提高,一般普适的(含强)TI介质中的多震相射线正、反演方法,则成为急需解决的问题。鉴于此,本文将基于各向同性介质多震相分区多步最短路径射线追踪算法推广到一般各向异性TI介质,结合相、群速度导数的一阶旅行时扰动方程,采用共轭梯度求解带约束的阻尼最小二乘问题,进而提出了一种利用多震相旅行时进行一般TI介质弹性参数反演的方法。井间地震数值实验结果表明,多震相旅行时联合反演可有效提高成像分辨率,验证了方法的有效性和正确性。

Multi-phase traveltime tomography in general anisotropic TI media: an example of crosshole tomography

Conventional ray tracing and traveltime tomography are almost based on a weak anisotropic media assumption, and only direct arrivals and their corresponding inversion are considered in a simple VTI media. With increasing requirements for high accurate exploration, it is instructive to solve the general (including strong) anisotropic TI media for both multi-phase ray tracing and inversion. For this reason, we put forward in this paper an algorithm for multiple arrival tracking in the general anisotropic media, which is incorporated with the first-order traveltime perturbation equation for phase and group velocity derivatives and an inversion solver (damping minimum norm, and constrained least square problem with the conjugate gradient approach) to form a traveltime inversion method using multi-phase arrival times for the general anisotropic media. Finally we show an example for crosshole traveltime tomography to verify the efficiency and accuracy of the proposed inversion method. Tomographic results indicate that the proposed algorithm can improve the imaging resolution with later arrival time information included in the elastic parameter reconstruction.