松辽盆地南部低阻储层特征及其形成机理

通过30块岩心样品的测试，对常规储层与低阻储层的岩性组成、物性、电性、微观孔隙结构及流体特征进行对比分析，剖析了低阻储层的形成机理。认为松辽盆地南部四方台和海坨子地区低电阻率储层形成的共同原因是：①均形成于三角洲（或扇三角洲）前缘的河口坝、远砂坝、席状砂等沉积微相中；②岩石颗粒细（粒度中值一般小于0.07 mm），泥质成分多（泥质含量普遍大于15%），岩性组合为粉砂岩、泥质粉砂岩、粉砂质泥岩，岩石孔隙结构较复杂；③粘土矿物含量较高，粘土矿物中高含伊/蒙混层、伊利石等矿物（相对含量一般大于70%）；④储层束缚水含量高（普遍大于20%）。此外，还有一些特殊原因。

Characteristics and Formation Mechanism of Low-resistivity Reservoirs in the Southern Songliao Basin

In order to study the formation mechanism of low resistivity reservoirs, 30 core samples are tested. The lithologic composition, physical properties, electrical properties, microscopic pore structure and fluid features of conventional reservoirs and low resistivity reservoirs are compared and the geologic settings for the formation of low resistivity reservoirs are discussed. The common causes of the low resistivity reservoirs in Sifangtai and Haituozi areas in the southern Songliao Basin are the followings: ① They are all formed in sedimentary microfacies, such as mouth bar, distal bar and sand sheet, in delta (or fan delta) front; ② The grain size is small, with a median grain diameter generally lower than 0.07 mm, the shale content is high, generally over 15%, the lithologic compositions are siltstone, argillaceous siltstone and silty mudstone, and the pore structures are relatively complex; ③ The content of clay is relatively high and the clay is rich in illite and mixed illite/smectite, with relative contents generally over 70%; ④ The irreducible water saturation is high, generally over 20%. In addition, there are also some specific causes.