断陷湖盆深水重力流水道的识别标志及沉积模式——以歧口凹陷歧南斜坡沙一段为例

以歧口凹陷歧南斜坡沙一段的深水厚层砂岩为研究对象,运用地震沉积学基本理论和方法,通过古地貌分析约束物源方向,结合岩心观测描述确定沉积相类型,应用地层切片、反演与三维可视化技术确定空间形态。结果表明:该区广泛发育的深水厚层砂岩为重力流水道沉积,包括滑塌岩、砂质碎屑流砂体与浊积岩3种类型重力流沉积的组合;顺北东向展布的断槽内呈大型条带状展布,可划分为水道中心微相、水道边缘微相和水下漫溢微相;岩心中可识别出7种岩相类型。在沉积特征分析的基础上,建立了发育于斜坡且由顺源断层控制的重力流沉积模式,分析了歧南斜坡重力流水道的成因及其油气成藏特征。研究认为重力流水道是该区一类重要的储集体,具有良好的成藏条件,该成果扩大了歧口凹陷油气勘探领域。

Identification Marks and Depositional Model of Gravity Flow Channel in Continental Rifted Lake Basin:A Case of the First Member of Shahejie Formation in Qinan Slope,Qikou Sag

Case study on the thick layer sandstone of the First Member of Shahejie Formation in Qinan slope, the authors analyzed the distribution characteristics of gravity flow channel in the continental rifted lake basin by the ideas and methods of seismic sedimentology.Combined with the regional geological setting,restaint provenance source,and core observation the types of sedimentary facies,stratal slice,seismic inversion and 3D visualization are determined.According to the study,the sand body should be the gravity flow channel sediments which could be the combination of slump rock, sandy debris flow,and turbidity flow.The gravity current sediment bands distribute along the half graben like faulted trough.In terms of the depositonal regime of gravity flow channel,the turbidity channel is subdivided into three types of microfacies:central channel,channel margin,and subaqueous overflow.A depositional model is established based on the integrated studies.Six lithological facies are recognized in the rock core.The authors discussed the genesis of gravity flow channel and analyzed its pool-formed characteristics.It is revealed that the gravity channel is an important reservoir with a good pool-formation combination and exploration potential in this area.This study indicates a new oil & gas exploring realm in Qikou sag.