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有机储集空间是页岩的重要储集类型,但对处于生油窗内的湖相页岩是否发育有机储集空间却缺少研究.系统采集处于生油窗范围内不同演化程度的湖相页岩样品,利用氩离子抛光样品制备技术,分别使用Quanta200扫描电镜及EDAX能谱仪联机和JSM-6700f冷场发射扫描电子显微镜对湖相页岩进行微观特征观察和岩石组分分析,背散射图像和二次电子图像均显示,页岩内大量发育呈暗色条带状的有机质-粘土-碳酸盐和有机质-粘土-硫酸盐混合体.该混合体内极易发育孔隙,从2 500~4 000m,该类孔隙连续分布,当埋深小于3 600m时,这类孔隙的尺度一般为微米级,但随着演化程度增高纳米孔隙增加,并且呈密集分布.混合体内孔隙的发育分别与页岩含油饱和度迅速增高及游离有机酸含量的增加同步,该类孔隙的发育不仅仅取决于生烃作用,它的形成是生烃转化和有机酸溶蚀共同作用的结果.上述结果表明,在生油窗范围内湖相页岩中,有机质与无机矿物作为整体共同演化且相互作用,在生烃与溶蚀叠合作用下形成了丰富的有机质-矿物混合体内储集空间,该储集类型对陆相页岩油气赋存具有重要意义.
Organic reservoir space is an important reservoir type of shale, but there is a lack of research on whether or not organic lacustrine reservoirs are developed in lacustrine shale within the oil window.The system collects lacustrine pages with different evolutionary stages within the oil window The rock samples were prepared by argon ion polishing. The microscopic observation and rock composition analysis of lacustrine shale were carried out using Quanta200 scanning electron microscope, EDAX EDS and JSM-6700f cold field emission scanning electron microscope respectively. The backscatter images and Secondary electron images show that there are a large number of dark-banded organic matter-clay-carbonate and organic matter-clay-sulphate mixed in the shale, and the porosity is very easy to develop in this mixture, ranging from 2 500 to 4 000 m When the depth is less than 3 600 m, the size of these pores is generally in the order of micrometers, but with the evolution of the pores increasing, the pores are densely distributed.The development of the pores in the mixture is related to the oil saturation of shale Rapid increase and the increase of free organic acid content simultaneously. The development of such pores does not depend solely on the hydrocarbon generation, but its formation is the result of the interaction between hydrocarbon generation and organic acid dissolution. The above results show that organic matter and inorganic minerals co-evolve and interact with each other in the lacustrine shale within the oil window, and abundant organic-mineral mixed reservoir space is formed under the superimposition of hydrocarbon generation and dissolution. This type of reservoir is of great significance for the occurrence of continental shale hydrocarbon.