东营凹陷泥页岩孔隙结构特征及其演化规律

Structure characteristics and evolution characteristics of pores in mud shale in Dongying Sag

泥页岩物质组成多样且孔隙结构复杂,明确其孔隙结构特征及其演化规律对预测泥页岩油气富集层段具有重要意义。为此,以东营凹陷S井泥页岩为研究对象,采用氮气吸附-压汞联合测孔法,获取泥页岩完整的孔径分布特征及不同类型孔体积等定量参数。结果表明:泥质粉砂岩以大孔为主,粉砂质泥岩和泥岩以介孔和微孔为主。通过分析矿物组分、有机组分与孔隙结构的关系,探讨孔隙结构发育的影响因素,发现泥页岩中黏土矿物含量和类型对介孔和微孔发育影响较大,碳酸盐类矿物对孔隙结构发育的影响受其成因控制;有机质丰度、类型等对孔隙结构的发育影响更显著。分析孔隙结构、矿物组分和有机组分的剖面演化特征,发现在埋藏演化过程中,矿物转化、有机质生烃及埋藏压实作用共同导致孔隙演化的多阶段性。

Mud shale material composition is variable and its pore structure is complex,thus,clarifying the characteristics,the influence factors and the evolution of nano-pores in shale is of great significance to predict the oil/gas enrichment intervals.Shale from Well S in Dongying Sag was studied with the combination of N2 adsorption and mercury intrusion methods,to obtain the pore size distribution,the volume of different type of pore,and other quantitative parameters.The results show that the argillaceous siltstone is dominated of macropore,and the silty mudstone and mudstone are mainly characterized by mesopore and micropore.By analysing the relationships among mineral composition,organic composition and pore structure,it is found that clay content and clay mineral type in mud shale have the most strong effect on micropore and mesopore.And the influence of carbonate minerals on the pore structure is controlled by its genesis.Furthermore,the total organic carbon(TOC),and organic matter type affect more strongly the pore structure of mud shale.By analyzing the evolution characteristics of pore structure,mineral composition and organic composition,it is found that mineral transformation,hydrocarbon generation of organic matter and burial compaction together lead to the multiple stages pore evolution during burial evolution.