基于走时约束的分频分步零偏VSP波动方程多参数反演

在地震勘探中,描述复杂介质的正演和反演问题通常包含许多反映介质不同特性的参数.同时获得这些参数对进行更准确的岩性描述和油藏预测具有重要的理论和现实意义.为了提高频率域黏弹性波动方程的零偏VSP多参数反演的精度,本文对多参数反演的可行性进行分析,明确了目标函数的敏感程度及参数之间的耦合情况,提出了一种基于走时约束的分频分步多参数反演策略.首先利用零偏VSP资料构建先验信息,然后分别利用高、低频数据进行两步反演,也就是"三个参数反演+五个参数反演"的过程,以提高反演的稳健性和精度.利用此方法可同时得到零偏VSP数据可靠的弹性波速度、密度和品质因子,为精确的时-深关系及含油气的解释和预测奠定基础,同时也可以为地面地震叠前反演提供可靠有效的约束,增强地面地震反演精度.

Multi-parameter inversion of frequency-divided zero-offset VSP wave equation based on traveltime constraint

In seismic exploration, forward modeling and inverse problems of describing complex media usually contains many parameters which reflect the different properties. In order to improve the accuracy of zero offset VSP multi-parameter inversion in the frequency domain, the feasibility of such inversion is analyzed. The sensitivity of the objective function and the coupling between the parameters are clarified, and a strategy for frequency-divided wave equation multi-parameter inversion based on traveltime constraint is proposed. First, the prior information is constructed by using the zero offset VSP data, then a two-step inversion is carried out on low-and high-frequency data, which is a process of "three parameter inversion + five parameters inversion", in order to improve the robustness and accuracy of the inversion. By using this method, the reliable elastic wave velocities, density and quality factors of the zero offset VSP data can be obtained simultaneously. It lays a foundation for accurate time depth relationship and interpretation and prediction of oil and gas. It can also provide a reliable constraint for the ground seismic pre-stack inversion and enhance accuracy of ground seismic inversion.