川东建南地区须家河组储层特征及其差异演化过程

Reservoir Characteristics and Differential Evolution Process of Xujiahe Formation in Jiannan Area,East Sichuan

川东建南地区须家河组储层非均质性极强,致密化程度极高,为了查明储层差异演化过程,剖析储层差异演化控制因素,运用岩石学和岩石地球化学的多种实验方法,在详细刻画储层岩石学特征的基础上,划分了储层成岩相类型,查明了不同类型砂岩的物性特征和孔隙结构特征,分析了储层的差异性演化过程.研究区砂岩可以划分为4种成岩相类型,即强压实相、溶蚀相、硅质胶结相和强钙质胶结相.溶蚀相砂岩物性最好,强压实相砂岩次之,硅质胶结相和钙质胶结相砂岩物性最差.碎屑组分的差异是造成储层非均质性强和差异性演化的重要原因.塑性岩屑含量的差异,导致早成岩时期压实减孔程度的不同;长石含量的差异,影响了砂岩中溶蚀强度和方解石胶结程度;石英含量的差异,控制了砂岩中硅质胶结作用的强弱;最终,使得储层演化有先有后,空间分布非均质.

The reservoir of Xujiahe Formation in the Jiannan area of East Sichuan basin is highly heterogeneous and the densification is extremely high.To clarify the process and the controlling factors of reservoir differential evolution,a variety of experimental methods of petrology and petrogeochemistry are used in this study.Based on the detailed description for petrology characteristics of the reservoir,the diagenetic facies are classified;then the rock properties and pore structures are characterized,and finally the reservoir differential evolution process is investigated.Sandstones in study area can be divided into four diagenetic facies,namely,tight compaction facies,dissolution facies,siliceous cementation facies and tight calcite cementation facies.Sandstones from dissolution facies have the best rock properties,followed by the tight compaction sandstone.Siliceous cementation sandstone and calcite cementation sandstone are highly densified with the poorest rock properties.The variations of detrital component are the key factors controlling the heterogeneity and differential evolution of the reservoir.The various contents of ductile rock fragments result in the different degrees of compaction and pore reduction in the early diagenetic period,while feldspar and quartz contents affect the dissolution and calcite cementation degree,and the siliceous cementation degree,respectively.Finally,the detrital component controls the evolution process of reservoir in a different time order,and results in the spatial heterogeneity for the distribution.