基于双约束的流体和岩性因子的叠前直接提取方法

Direct extraction of fluid and lithology factors based on double constraints using pre-stack seismic inversion

叠前反演是从叠前数据中提取岩性和流体信息的重要途径,而反射系数近似方程是叠前反演的基础。本文重新推导了纵波、转换波的反射系数近似方程,得到了由流体因子F和岩性因子μρ构成的反射系数近似方程,通过对方程的精度分析,验证了新方程的可靠性;在求解过程中,结合贝叶斯理论引入了多变量柯西约束做为模型参数的先验信息,稳定了反演结果,提高了反演的分辨率;为了得到可靠的低频信息,在目标函数中构建了低频约束项,进一步提高了反演结果的精度。模型测试和实际应用结果均表明,新提出的反演方法可以从地震数据中同时直接提取高精度的F和μρ信息,为储层识别和流体检测提供了一种新的计算思路。

Pre-stack inversion is a significant method for extracting lithology and fluid information from pre-stack seismic data. And the reflection coefficient approximation equation is important for pre-stack inversion. In this paper, the approximation equations of the P-wave and S-wave reflection coefficients are re-derived. The new equations consist of the fluid factor F and the lithology factor μρ. An accuracy analysis of the novel equations is carried out to verify the reliability of the proposed equations. In the process of inversion, combined with Bayesian theory, the trivariate Cauchy distribution constraint is introduced as the a priori information of the model parameters, which can stabilize the inversion results and improve their resolution. In order to obtain reliable low-frequency information, the low-frequency constraint term is constructed and added in the objective function to further improve the accuracy of the inversion results. Both the model and the field data tests show that the proposed inversion method can directly extract high-precision parameters of F and μρ from the seismic data, which provides a new calculation concept for reservoir characterization and fluid discrimination.