摘要： 综合利用岩心、铸体薄片、扫描电镜等多种资料,对鄂尔多斯盆地正宁地区三叠系延长组长9油层组储集层的岩石类型、成岩作用类型、成岩相分布特征及主控因素进行了系统研究。延长组长9油层组储集层的岩石类型为细—中粒岩屑质长石砂岩和长石质岩屑砂岩,成岩作用类型主要为压实作用,同时还有绿泥石、方解石、铁方解石及硅质胶结作用,方解石交代作用和少量的溶蚀作用,储集层目前处于中成岩A期。根据层理频率和塑性颗粒含量将岩石划分为高频层理富片状塑性颗粒粉—细砂岩岩石相和低频层理富刚性矿物细—中砂岩岩石相,前者分布于水下分流河道边部,发育压实致密成岩相;后者形成于水下分流河道主河道和河口坝。根据砂体结构可划分为厚层单砂体和厚层多砂体。厚层单砂体为单期形成的河道或河口坝砂体,上部以方解石充填胶结成岩相为特征,下部以绿泥石衬边胶结成岩相为特征;厚层多砂体为多期砂体冲刷叠置形成,发育方解石绿泥石充填胶结成岩相。塑性颗粒含量对压实作用强度影响最大,叠加碳酸盐胶结致使储集层质量变差,而早期绿泥石环边胶结抑制压实作用,是有利储集层发育的重要条件。综合评价表明,延长组长9油层组有利储集层发育于绿泥石衬边胶结相,其次为绿泥石和方解石充填胶结相,最差储集层为方解石充填胶结相和压实致密相。

关键词: 延长组, 储集层, 成岩作用, 成岩相, 正宁地区, 鄂尔多斯盆地

Abstract: Based on the description of the core,casting thin sections,scanning electron microscopy and other data,the rock types,diagenesis types,distribution characteristics and main controlling factors of diagenetic facies were systematically studied for the Member 9 oil-bearing interval of Triassic Yanchang Formation in the Zhengning area of the Ordos Basin. The rock types of the Member 9 oil-bearing interval are mainly composed of fine-to medium-grained lithic arkose and feldspathic lithic sandstone. The diagenesis types mainly include compaction,chlorite cementation,calcite cementation,ankerite cementation,siliceous cementation,calcite replacement and dissolution. The Member 9 oil-bearing interval in the study area is currently in the middle diagenesis stage A. According to the stratification frequency and plastic mineral content,the rock type can be divided into high-frequency stratification flake-like plastic-mineral rich silt-to fine-grained sandstone rock facies and low-frequency stratification rigid-mineral rich fine-medium-grained sandstone rock facies. The former distributed at the edge of underwater distributary channel with the densely compacted diagenetic facies are developed,while the latter formed in the main channel of underwater distributary channel and mouth bar. The thick single sand-body and the thick multi-storey sand-body can be divided according to the sand-body structure. The thick single sand body is a single channel or mouth bar sand-body,which is characterized by calcite-filling cementation phase in the upper part and chlorite-lining cementation phase in the lower part. The thick multi-storey sand-body is formed by multi-stage channel sand-body scour and superposition,which develops calcite-chlorite-filling cementation phase. The ductile grain content is the most important factor influencing compaction strength,resulting in a poor reservoir quality superposed carbonate cementation and the inhibition of the compaction by the early chlorite-lining cementation is an critical condition for the favorable reservoir development. The comprehensive evaluation shows that the favorable reservoir of Member 9 oil-bearing interval of Yanchang Formation developed with the chlorite-lining cementation facies. The next is the chlorite-calcite-cementation filling phase. The reservoirs with the lowest quality are developed at the calcite-filling cementation phase and compacted dense phase.

Key words: Yanchang Formation, reservoir, diagenesis, diagenetic facies, Zhengning area, Ordos Basin

中图分类号: 

• TE122.2+4