粒度概率曲线特征及岩相组合分析在沉积环境研究中的应用

Application of Probability Cumulative Grain Size Curves and Lithofacies Association to Sedimentology

锦州油田馆陶组砂岩属于辫状河沉积,储层发育并表现为大套砂岩特征。经岩心观察可知,纵向上粒度差异明显,揭示了沉积过程中沉积环境和水动力条件的变化,但自然伽马、自然电位以及电阻率曲线多为光滑箱型,可见常规测井曲线在沉积环境分析中存在局限性。通过岩心观察识别出5种岩相、3种组合类型及3种沉积微相,系统总结了利用丰富的岩心、壁心粒度分析资料绘制的大量概率累积曲线特征,借助岩相将粒度概率曲线类型标定、划分为3种类型,建立了不同沉积条件下的粒度概率曲线图版,用于辅助研究区沉积微相的划分。

Guantao Formation in Jinzhou oilfield,which its sedimentation belongs to braided-river facies,mainly consists of massive sandstones.Core observation displays an obvious difference among grain size in longitudinal direction,also re-vealing some variations of both depositional environment and hydrodynamic condition.However,smooth box-like natural GR,SP,and resistivity curves demonstrate that conventional logging curves have some disadvantages in depositional envi-ronment analysis.Through core analysis,we at first identified five lithofacies,three lithofacies associations,and three micro-facies,and then systematically summarized certain characteris-tics of probability cumulative grain size curves on the basis of plenty of core and sidewall core data,thirdly classified these curves into three types with the help of lithofacies,final-ly established probability grain size curve plates under vari-ous depositional environments in order to assist microfacies classification.