东海西湖凹陷平湖主断裂下盘砂砾岩储层特征及主控因素

Characteristics and Controlling Factors of Glutenite Reservoir in the Footwall of Major Pinghu Fault in Xihu Sag,East China Sea

利用岩心、薄片、扫描电镜等资料,运用岩石学、沉积学等方法对东海平湖地区平湖主断裂下盘砂砾岩储层进行了分析,认为储层以砂质砾岩和砾质砂岩为主,结构成熟度和成分成熟度都不高;孔隙类型以粒间孔为主,其次为粒间溶孔和粒内溶孔;储层储集性能总体上是中孔中渗到低孔低渗。该区砂砾岩沉积相为近岸水下扇,可进一步分为扇根、扇中和扇缘亚相,其中以扇中亚相辫状水道微相储层物性最好,可提供最有利的油气储集空间。经过对研究区成岩机理研究认为,影响研究区砂砾岩储层的主要成岩作用为压实作用、胶结作用和溶解作用。压实作用和胶结作用为破坏性的成岩作用,溶蚀作用为建设性的成岩作用。岩石结构及岩石颗粒成分均降低砂砾岩的孔隙空间。

Based on the data of cores,thin sections,scanning electron microscopy,petrology and sedimentology,the author analyzed the characteristics of glutenite reservoirs in the footwall of Pinghu major fault in Xihu Sag,East China Sea,and thinks that the reservoirs are mainly composed of sandy gravels and gravelly sandstones,with middling maturity of texture and composition;the pore types are dominated by intergranular pore,followed by intergranular dissolved pore and intragranular dissolved pore;reservoir performance is generally in the scope of medium porosity and permeability to low porosity and permeability.The sedimentary facies of glutenite in the area belongs to the coastal subaqueous fan,and can be further divided into root fan,middle fan and marginal fan,of which the reservoirs of braided channel microfacies in the middle fan are the best in physical properties,and can supply the favorable reservoir space for oil and gas.The study of diagenesis mechanism in the study area shows that compaction,cementation and dissolution are the main diageneses that affect the reservoir property.Compaction and cementation are destructive diagenesis,and dissolution is constructive.The texture and composition of rock particles reduce the pore space of glutenite.