鄂尔多斯盆地西北部长9储层沉积特征及地质意义

Sedimentary characteristics and geological implication of Chang-9 reservoir in northwest of Ordos basin

综合分析岩心、测井与分析化验等测试结果,认为鄂尔多斯盆地西北部长9储层沉积期整体处于水上沼泽环境,主要发育辫状河三角洲平原亚相,沉积受西北和东北两个物源体系控制,以西北物源为主。岩石学研究表明,长9油层砂岩类型主要为长石砂岩和岩屑长石砂岩,成分成熟度较低,结构成熟度中等;受沉积影响,长9沉积砂体在纵向上结构表现为无粒序变化均一型和复合粒序型两种特征,分流河道微相为主要储集体,易于石油聚集成藏。

According to cores,logging and testing analysis,the sedimentary characteristics of Chang-9 reservoir in northwest region of Ordos basin were studied.The results indicated it wholly belonged to marsh environment and mainly developed braid-river delta plain subfacies.The sedimentation was controlled by two provenance systems in northwest and northeast,especially the northwest provenance.The petrographic study showed the sandstone in Chang-9 reservoir were mainly of arkose and lithicarkose with low compositional maturity and moderate structural maturity.Affected by the sedimentation,the sand body of Chang-9 reservoir was vertically characterized by uniform type without graded change and composite graded type.The main reservoir body was of distributary channel microfacies and it was good for oil accumulation.