砂砾岩沉积特征分析及有利储集相带确定——以玛北斜坡区百口泉组为例

Sedimentary Characteristics of Glutenite and Its Favourable Accumulation Facies: A case study from T_1b,Mabei Slope,Junggar Basin

为明确砂砾岩复杂储层的沉积特征及有利储集相带分布,通过岩心、测井、地震、实验分析等资料综合研究,认为玛北斜坡区百口泉组属近源快速堆积的扇三角洲沉积体系,主要发育扇三角洲平原辫状河道、扇三角洲平原/前缘砂质碎屑流、扇三角洲前缘近岸水下分流河道、远岸水下分流河道、河口坝五种主要沉积微相类型。发育牵引流、重力流两种搬运机制。主要发育夏子街扇、黄羊泉扇二大主扇体,夏子街扇细分为风南10、夏72、玛7三条支扇,西部的风南10支扇、东部的玛7支扇发育重力流(砂质碎屑流)沉积。夏72支扇位于玛北鼻状凸起上,鼻状凸起背景下发育的低缓沟槽控制着牵引流水系的展布。储层的成岩作用(压实、胶结)强度与沉积作用(泥杂基含量、粒度)关系密切,泥杂基含量、粒度为储层储集性能的主控因素。有利储集相带受沉积机制、沉积微相双重控制,重力流(砂质碎屑流)沉积整体物性最差;牵引流沉积视不同沉积相带,扇三角洲平原辫状河道、扇三角洲前缘远岸水下分流河道物性较差;扇三角洲前缘近岸水下分流河道、河口坝物性最优,优质储层主要分布在扇三角洲前缘近岸水下分流河道相带内。

To clear the sedimentary characteristics of glutenite and the distribution of favourable accumulation facies,With the integrated study of core,logging,seismic and experimental analysis,this paper draw conclusions that the sedimentation in T1 b,Mabei Slope subordinate to fan delta deposition,including five sedimentary microfacies as follows： braided-stream channel in fan delta plain,sandy-debris flow in fan delta plain or fan delta front,nearshore underwater-distributary channel,offshore underwater-distributary channel,and estuary dam in fan delta front. There developed two mechanism named tractive current and gravity current,and mainly developed Xiazijie fan and Huangyangquan fan. Xiazijie fan is divided into three branch-fans named FN10,XIA72,MA7. FN10 branch-fan and MA7branch-fan are mainly developed sandy-debris flow. XIA72 branch-fan locate in Mabei heave. The slow grooves developed in Mabei heave controlled the distribution of tractive current. The intensity of reservoir diagenesis（ compaction and cementation） is closely related to deposition（ matrix content and granularity）. Matrix content and granularity are main controlling factor of accumulation property. Transportation mechanism and sedimentary microfacies controlled the distribution of favourable accumulation facies. Sandy-debris flow deposition is poor reservoir. The different sedimentary facies belt in tractive current have different accumulation property. Braided-stream channel in fan delta plain and offshore underwater-distributary channel are sub-poor reservoir. Nearshore underwater-distributary channel and estuary dam in fan delta front are the best reservoirs. High-quality reservoir are mainly located in nearshore underwater-distributary channel,and fan delta front.