基于改进Xu-White模型的富有机质页岩横波预测方法研究

Shear wave prediction method of organic-rich shale based on improved Xu-White model

横波速度是储层表征描述、AVO分析和流体识别的重要信息。干酪根是富有机质页岩的重要成分且具有非固体非流体的特殊弹性性质,常规处理方法是将其等效为流体。这里提出了一种基于变化孔隙纵横比Xu-White模型的富有机质页岩横波预测方法,首先将干酪根同时等效为基质矿物和孔隙流体引入模型中,然后利用模拟退火粒子群算法,在约束条件下,反演出变化孔隙纵横比,并以变化孔隙纵横比初始化,模型构建富有机质变化孔隙纵横比Xu-White模型,最后结合测井信息与岩石物理模型预测横波速度。将该方法应用于中国西南部四川盆地东南焦石坝地区某井位,通过对比固定孔隙纵横比Xu-White模型方法与干酪根流体等效的变化孔隙纵横比Xu-White模型预测结果,验证了该方法的适用性和准确性。本方法将为富有机质页岩的研究提供更准确的横波速度资料。

Shear wave velocity is essential information for reservoir characterization,AVO analysis,and fluid identification.Kerogen is a crucial component of organic-rich shale and has special elastic properties of non-solid and non-fluid.The conventional prediction method is equivalent to fluid.This paper proposes a shear wave prediction method for organic-rich shale based on the Xu-White model with variable aspect ratio.Firstly,kerogen is equivalent to the model's matrix minerals and pore fluid.Then,a simulated annealing particle swarm optimization algorithm is used to inverse the variable aspect ratio under constraint conditions.Thirdly,the Xu-White model with variable aspect ratio is constructed by initializing the variable aspect ratio model.Finally,the shear wave velocity is predicted by combining logging information and the rock physics model.The method is applied to a sound site in Jiaoshiba area of southeast Sichuan Basin in southwestern China.The prediction results of Xu-White model with fixed aspect ratio and Xu-White model with variable aspect ratio equivalent to kerogen fluid are compared to verify the applicability and accuracy of the method.This method will provide more accurate shear wave velocity data for studying organic-rich shale.