鄂尔多斯盆地陇东地区延长组纵向储层质量差异及主控因素分析

综合应用多种岩心分析资料对陇东地区上三叠统延长组主力勘探目的层长8和长6油层组的岩石组构、岩石组分与储层质量差异进行了对比分析,探讨了岩石组构与岩石组分对储层质量差异的控制作用。长8末期一次显著的构造事件导致长8与长6油层组储层岩石组分和组构特征发生了明显的变化。相较于长8油层组,长6油层组粒度较细、杂基含量较高,使得原始渗透率较低,并导致更强的压实作用,使得其最终储层质量较差;塑性组分含量高,经历了较强的压实作用,原生粒间孔保存较少,并不利于后期溶蚀作用对储层进行改造;喷发岩岩屑含量低使储层早期绿泥石膜胶结相对不发育;富含白云岩岩屑为晚期含铁碳酸盐胶结物的形成提供了物质基础,使得长6油层组储层进一步致密化;长石含量高使得自生伊利石含量高,其形成的大量微孔隙导致了渗透率的大幅度降低。

Reservoir quality and its controlling factors of Chang 8 and Chang 6 members in Longdong Area, Ordos Basin

With the integrated application of multiple data of core analysis,the rock fabrics,rock compositions and reservoir quality of the Chang 8 and Chang 6 oil-bearing formation of Longdong area,which deposited as the main exploration layers of upper Triassic,was analyzed to understand the control of the rock fabrics and rock compositions on reservoir quality.The results show that an intense tectonic event happened at the end of sedimental phase of Chang 8 strata in Odors Basin made a great difference on rock fabrics and compositions of Chang 6 and Chang 8 reservoir.Compared with Chang 8,Chang 6 has finer grains and higher contents of matrix,which make its low original permeability and more intensive compaction;the higher content of plastic components and rarely preserved primary intergranular pores are both of disadvantage to the improvement of reservoir quality by later dissolution;the low contents of eruptive rock debris lead to relatively poor development of early chlorite film cement in reservoir;while the high contents of dolostone debris result in the formation of later ferri-carbonate cements and further densification of Chang 6 reservoir;a large number of micro-pore caused by authigenic illite cementation owing to the high contents of feldspar results in a significant reduction in permeability of Chang 6 reservoir.