徐家围子断陷营城组火山岩岩性、储层岩石物理弹性参数特征分析

本文通过测量岩样在干、饱含气和饱含水状态下的纵波速度v_P、横波速度v_S和密度ρ等参数，研究不同岩性含不同流体时纵波速度和横波速度的变化规律，得出适用于徐家围子地区火山岩横波速度的预测方法，即分岩性和含不同流体进行分层段模拟，为测井岩石物理分析提供精确的横波速度曲线；在难以区分具体火山岩岩性的现实条件下，测井岩石物理首次引入"岩性组"的概念，利用横波速度、密度、拉梅系数三个参数把营城组地层岩性划分为不同的岩性组；在岩性分组识别的基础上，分析同一岩性组的储层和气层的敏感参数，对比不同岩性组分析结果发现，储层具有低密度特征，气层都具有低泊松比特征，形成了一套完整的火山岩岩性区分、储层与气层识别的思路和方法，为火山岩储层高精度预测奠定了基础。

Volcanic lithology and reservoir identification based elastic wave characteristics analysis in Yingcheng Formation,Xujiaweizi Depression

Volcanics are characterized by different types of lithology and strong heterogeneity,therefore volcanic lithology and reservoir identification are very difficult.We propose in this paper an approach to predict volcanic lithology and reservoirs in Yingcheng Formation,Xujiaweizi Depression based on elastic wave characteristics analysis.First we analyze changes of P-and S-wave velocity in different lithologic rocks with different fluids to provide accurate S-wave curves.Then we introduce "lithology group" in rock physics study for complicated volcanic lithology.We use three parameters such as S-wave velocity,density,and lambda to divide Yingcheng Formation lithology into four rock groups,namely,mudstone,basalt (basalt,basaltic andesite),andesite (andesite,trachyte,dacite),and rhyolite (rhyolite,tuff,conglomerate,volcanic breccia).Finally we analyze reservoir and gas sensitive elastic parameters in different lithological groups.It is found that oil reservoirs show low-density characteristics while gas-bearing beds have low-Poisson's ratio characteristics.The proposed approach is successfully applied to identify volcanic lithology,oil reservoirs,and gas-bearing beds in Xujiaweizi Depression,which lays a solid foundation for the accurate volcanic reservoir prediction.