塔中地区碳酸盐岩与碎屑岩储层物性差异及主控因素

通过对塔里木盆地塔中地区55口探井的岩心观察及200多张铸体薄片的鉴定,分析了92口探井的孔渗、岩石压汞及测井解释成果,及其石炭系—志留系碎屑岩储层与奥陶系碳酸盐岩储层之间物性特征的差异,结合地质背景讨论了造成这些差异的主控因素。结果表明研究区碎屑岩储层总体为低孔低渗—中孔中渗,碳酸盐岩储层总体为低孔低渗—特低孔特低渗,两类储层的孔隙度、渗透率和孔喉半径三个物性特征参数之间的相关性完全不同。原始沉积作用是两类储层物性差异形成的基础,宏观上体现在储层沉积相带的不同,微观上体现在储层矿物组分、结构的差异;后期成岩作用,包括压实、溶蚀、胶结及构造裂缝改造是两类储层物性差异形成的关键,相对于碎屑岩储层物性参数大小的改变,碳酸盐岩储层物性受溶蚀、胶结、构造裂缝改造的影响较大,相对而言受压实作用的影响较小。两类储层物性差异主控因素的对比研究表明碎屑岩储层应侧重于优质沉积相带中原生孔隙油气勘探;碳酸盐岩储层应侧重于次生孔隙油气勘探。

Physical Properties Differences and Key Controlling Factors of the Clasolite Reservoirs and Carbonate Reservoirs in Tazhong Area

This paper reports data from observation of 55 wells and identification of more than 200 casting thin sections, mercury injection data analysis and logging interpretation of 92 wells and analyzed physical properties differences between the Silurian- Carboniferous clasolite reservoirs and the Ordovician carbonate reservoirs in the Tazhong area. Key controlling factors for the physical properties differences were discussed based on geological setting. The results showed that the clasolite reservoirs have medium-low porosity and medium-low permeability, and the carbonate reservoirs have lowto ultra-low porosity and lowto ultra-low permeability. The correlations among porosity, permeability and pore-throat radius are totally different for the two different types of reservoirs. The physical properties differences were controlled by sedimentation, which embodies sedimentary facies difference from macroscopic view and minerals composition difference and grain size from microscopic perspective. Besides sedimentation, physical properties differences are mainly controlled by compaction, dissolution, cementation and fracture rebuilding effect. Compared with the variation of physical properties of clasolite reservoirs, the carbonate reservoirs are more likely affected by dissolution, cementation and fracture rebuilding effect, and are more difficultly affected by compaction. Comparative studies of key controlling factors of the physical properties show that clasolite reservoirs should focus on primary pore for petroleum exploration, while carbonate reservoir should on secondary pore.