四川盆地震旦系灯影组丘滩体储层沉积模式与物性特征

Sedimentary Models and Physical Properties of Mound-Shoal Complex Reservoirs in Sinian Dengying Formation,Sichuan Basin

研究丘滩复合体沉积模式有助于预测四川盆地灯影组优质储层.基于钻井和露头资料,通过微观薄片鉴定,发现丘滩体主要的岩石结构为藻白云岩,并可进一步细分为5种微相:丘基、丘核、丘坪、丘盖和丘翼.识别出3种典型的微相组合类型,包括反映加积的"丘基-丘核-丘坪"序列,反映迁移的"丘基-丘核-丘翼"序列,反映终止的"丘基-丘核-丘盖"序列.结合沉积相带分布,将灯影组丘滩分为加积型台缘丘滩、迁移型台缘丘滩、台内丘滩、台内台坪4种类型.其中加积型台缘丘滩体主要沉积"丘基-丘核-丘坪"序列,旋回性明显,丘核多发育格架残留孔、洞,并在反映储集性能的储层总厚度、孔隙度、渗透率等方面均有优势,是四川盆地灯影组最有利的丘滩储集体.

Mound-shoal complex sedimentary models are important for the high-quality reservoir exploration of the Dengying Formation in the Sichuan basin.Based on core and outcrop profile and thin section observation,it is found that the main rock type of the mound-shoal complex is cyanobacteria dolostone.The mound-shoal complex consists of five microfacies including mound base,mound core,mound flat,mound cap and mound flank.There are three types of vertical combination rules of these microfacies,namely,the mound base-core-flat sequence reflecting aggradation,the mound base-core-flank sequence reflecting migration and the mound base-core-cap reflecting termination.According to the distribution of sedimentary facies,the mound-shoal complex of the Dengying Formation is divided into four types including aggradation platform margin mound-shoal complex,migration platform margin mound-shoal complex,platform interior mound-shoal complex and platform interior flat.The study shows that the aggradation platform margin mound-shoal complex mainly deposits the mound base-core-flat sequence,with obvious cyclicity.Its mound core develops a large number of framework residual pores and holes.Due to its advantages in total reservoir thickness,porosity and permeability,it is concluded that the aggradation platform margin mound-shoal complex is the high-quality reservoir of the Dengying Formation in the Sichuan basin.