马岭地区长81优质储层控制因素及分布规律

Control factors and distribution regularity of Chang 81 high quality reservoir in Maling area,Ordos Basin

马岭地区上三叠统延长组长81储层整体为低孔、特低渗储层,局部发育相对高孔高渗的优质储层,为了弄清优质储层的成因机理及分布规律,通过钻井资料,铸体薄片、扫描电镜及高压压汞等分析方法,对长81沉积相与砂体展布、储层岩石学、孔隙结构及成岩作用等进行了研究。结果表明,马岭长81期浅水三角洲前缘水下分流河道微相发育,多期水下分流河道叠加沉积形成了连片分布的有利储集砂体;压实作用和碳酸盐、伊利石胶结作用形成了长81储层的低孔低渗背景,长石溶蚀作用、绿泥石膜胶结作用使低渗背景上发育了相对高孔高渗储层。将长81储层分为Ⅰ,Ⅱ,Ⅲ,Ⅳ类,其中Ⅰ,Ⅱ类储层为相对高孔高渗的优质储层,约占储集砂岩的45%,主要分布于主水下分流河道沉积微相,同时长石溶蚀或绿泥石膜胶结成岩作用发育的地区。有利沉积、成岩作用共同控制了优质储层的形成与展布,为长81下步勘探部署指明了方向。

The Chang 81 interval of the Upper Triassic Yangchang Formation is a typical low-porosity,low-permeability reservoir in Maling area,Ordos Basin.The Chang 81 interval in the local region is a high quality reservoir with higher porosity and permeability,and the high quality reservoir is often the oil enrichment region.The drilling data,casting thin section,scanning electron microscopy and high pressure Hg injection are applied to analyze the sedimentary facies,sand body distribution,reservoir lithology,physical property,pore structure and diagenesis,in order to explore the formation mechanism and distribution of Chang 81 high quality reservoir.The article suggests that the underwater distributary channel microfacies of shallow water delta front was developed in Chang 81 period,and a continuous distribution of favorable reservoir was formed by multiple periods of underwater distributary channel deposits.The compaction,carbonate and illite cementation formed a low-permeability condition of Chang 81 reservoir,and the feldspar dissolution and chlorite cementation formed a reservoir with relatively higher porosity and permeability in the low-permeability background.The Chang 81 reservoir in Maling area can be divided intoⅠ,Ⅱ,Ⅲ,Ⅳclasses.ⅠandⅡclasses of reservoir with higher porosity and permeability account for about 45%of the reservoir sandstone,belonging to the high quality reservoir.The high quality reservoir is mainly distributed in the sedimentary microfacies of main underwater distributary channel,and the feldspar dissolution and chlorite cementation diagenesis was also developed in the sandstone formed by the main underwater distributary channel.The formation and distribution of the high quality reservoir are mainly controlled by favorable sedimentation and diagenesis,and the research results has provided a dependable clue for the next Chang 81 exploration in this area.