低频次叠加的同生溶蚀作用对滩相储层发育的控制——以川中栖霞组为例

The control of syngenetic dissolution of low-frequency superposition on the development of shoal facies reservoir:a case study of Qixia Formation in central Sichuan

川中地区栖霞组油气勘探已获得突破,但栖霞组优质储层类型及其形成机理尚不明确。文中综合利用川中高石梯-磨溪地区的岩心、录井、测井等资料及各类白云岩样品的地球化学测试数据,结合构造背景和沉积演化特征,对该地区栖霞组储层特征及其形成机理进行了研究。结果表明:该地区栖霞组储层发育晶粒白云岩、颗粒白云岩、斑状白云岩、砂屑灰岩、微亮晶球粒灰岩。储集空间以晶间孔、晶间溶孔和溶洞为主。储层类型包括溶洞型、溶孔-溶洞型和溶孔型。溶洞发育的白云岩、亮晶砂屑灰岩和微亮晶球粒灰岩储层对产能贡献明显,为该地区的优质储层。栖霞组优质储层发育于开阔台地的颗粒滩微相,主要受到古地貌缓坡部位的低频次叠加的同生溶蚀作用控制。根据储层演化过程建立了川中地区栖霞组优质储层发育模式。研究成果对于下一步分析川中地区储层分布规律提供了地质依据。

A breakthrough has been made in the exploration of the Qixia Formation in the central Sichuan Basin,but the type and formation mechanism of the Qixia formation reservoir with high quality are not clear yet.In this paper,the reservoir characteristics and formation mechanism of the Qixia Formation in Gaoshiti-Moxi area of central Sichuan basin are studied by using core,logging data and geochemical test data of various dolomite samples,combined with tectonic background and sedimentary evolution characteristics.The results show that the lithologies of the Qixia Formation in this area include crystalline dolostone,grain dolostone,dolomitic limestone,intraclastic limestone,bioclastic limestone and microsparite pelletoid limestone.The void spaces are mainly composed of intercrystalline pore,intercrystalline dissolved pore and karst cave.The reservoir types include cave,dissolved pore-cave and pore.Dolomite,intraclastic limestone and microsparry pelletoid limestone reservoirs with karst caves contribute significantly to productivity and are the high-quality reservoirs in this area.The high quality reservoir of Qixia Formation was developed in the shoal microfacies of the open platform,which was mainly controlled by syngenetic dissolution of low-frequency superposition of the shoal located on the high position of paleogeomorphology.Based on the reservoir evolution process,the development model of Qixia Formation reservoir in central Sichuan Basin was established.This study provides geological basis for further study of reservoir distribution in central Sichuan Basin.