东营凹陷古近系沙四上亚段滩坝储层特征及次生孔隙展布模式

东营凹陷沙四上亚段滩坝砂体广泛发育,平面上呈带状分布。滩坝砂体储层中次生孔隙是形成有效储层的重要条件,研究区存在的次生孔隙主要包括碳酸盐溶蚀孔隙和石英溶蚀孔隙两种类型,分属于两种不同流体成因。根据对不同滩坝沉积区储层次生孔隙和成岩作用的研究发现东营凹陷不同构造位置次生孔隙的成因类型不同,这是由于滩坝砂体中储层的固体和流体性质存在差异。固体性质的差异一般是由于沉积体距离物源的远近和沉积环境的不同造成的,而流体性质的差异主要是沉积体附近断层的连通性和活动性造成的。因此滩坝砂体的次生孔隙成因在横向上也相应地呈现出带状分布的特征:砾质滩坝主要为酸性成岩作用主导次生孔隙发育带,近岸滩坝主要属于酸碱共同作用次生孔隙发育带,远岸滩坝和中央共振带滩坝主要是碱性成岩作用次生孔隙发育带。

Reservoir characters and secondary pore distribution of beach-bar of the upper part of the fourth member of Shahejie Formation of Paleogene in Dongying Depression

The beach-bar sand bodies in the upper fourth member of the Eocene Shahejie Formation(the upper Es4)in Dongying Depression exhibit zonal distribution in a plane.The secondary pore developed in beach-bar sand bodies in the study area is an important factor to form favorable reservoir.The secondary pores can be mainly divided into carbonate dissolution pores and quartz dissolution pores,which were respectively formed in two different fluid environments.Based on the study of the secondary pore and the diagenesis in different beach-bar sedimentary areas,it is considered that the genetic types of the secondary pore vary in different structural locations in Dongying Depression,as the solid and fluid properties are highly different in the reservoir of beach-bar sand bodies.The differences of solid properties are caused by the distance from the sedimentary body to the provenance and the variation of sedimentary environments,while the differences of fluid properties result from the connectivity and activity of faults near the sedimentary body.Therefore,the secondary pore of beach-bar sand bodies shows corresponding zonal distribution laterally:the secondary pore zone developed in the gravel beach-bar was mainly controlled by acid diagenesis;the secondary pore zone existed in the coastal beach-bar was affected by interaction of acid and alkaline diagenesis;and the secondary pores in the offshore and the central resonance zone beach-bar reservoir were mainly affected by alkaline diagenesis.