运用极值搜索法模拟地震勘探中的二维随机溶洞介质

缝洞型储层是一种很重要的油气储层,但其非均质性很强,目前的随机介质理论已经无法描述缝洞型介质,需要进一步发展缝洞介质建模理论。首先给出了极值搜索法建立二维随机溶洞介质的基本理论;其次,以目前常用的4种随机介质为基础,运用极值搜索法构造了4种二维随机溶洞介质模型;最后,以高斯型随机介质为例,通过建立几种二维随机溶洞介质模型来讨论自相关长度、孔隙度、分区边长对模型的影响。模拟的结果表明,通过选择不同的参数,极值搜索法可以更加方便、灵活、完整地模拟复杂溶洞介质模型。针对渤海某地区浊积扇非均质性强的特点,利用极值搜索法建立了随机溶洞介质,对浊积扇的非均质性进行精细刻画。正演模拟结果表明,浊积扇地震剖面上的反射特征与物源的距离关系密切,从而为浊积扇的识别提供了一定的参考依据。

Simulation of 2-D random cavern medium in seismic prospecting using extreme search method

Fracture-cavern reservoir is a very important oil and gas reservoir, but its heterogeneity is very strong. Current random medium theory can not be used to describe cavern medium. Firstly, we give the basic theory of establishing 2-D random cave medium with extreme search method. Further more, we use extreme search method to construct four kinds of 2-D random cave medium model based on random medium in common use. Finally, we take Gaussian random medium for example to construct some 2-D random cave medium models to discuss the impact of autocorrelation length, porosity and section length on the simulation results, and find that simulating 2-D random fracture-cave medium upon extreme search method is convenient, flexible and accurate by choosing different parameters. The turbidite fan has very strong heterogeneity in some area of Bohai Sea, we establish random cave medium with extreme search method and describe the turbidite fan accurately. The result of seismic forward modeling shows that the reflectance signature of turbidite fan on the seismic profile has a intimate relationship with provenance distance, which can provide a reference for the identification of turbidite fan.