Abstract: The results of the conventional and special experiment on the parameters such as porosity,permeability,capillary pressure,wettability,grain size of cores got from low-resistivity formations of A Oilfield were analyzed.The low-resistivity beds in this oilfield were mainly controlled by some factors including high cation exchange capacity of smectite or mixed illite-smectite,high irreducible water saturation in micro-porosity system,existence of trace pyrite.The porosities of conductive beds ranged from 15.0 percent to 28.2 percent,and the permeability values were less than 0.03μm².Although porosity exponent was only 0.530,the lithologic constanta was 6.363.The relationship between resistivity index and water saturation showed a non-liner pattern in dual-logarithm coordinate.The saturation exponent ranged from 1.01 to 1.10.The saturation exponents corrected by cation exchange capcity ranged from 1.56 to 1.65.The CT scanning technique and SEM are useful to determinate the microstructure of rocks and the distribution of pores and minerals.

Key words: low-resistivity formation, influencing factors, porosity, permeability, capillary pressure, scanning electron microscope, CT scanning

摘要： 对A油田低电阻率油层岩心常规和特殊的实验结果表明,该油田的低电阻率油层主要有3个影响因素:①储层中粘土矿物蒙脱石和伊蒙混层的高阳离子交换量直接导致了电阻率的降低;②储层中大量微孔隙的存在导致了高的束缚水饱和度,也影响了储层的电阻率;③微量黄铁矿的存在使储层电阻率降低.储层的孔隙度为15.0%～28.2%,但是渗透率较低,一般小于0.03μm².储层的阳离子交换量较高,孔隙度指数仅为0.530,而岩性系数a为6.363.电阻增大率与含水饱和度在双对数坐标中存在明显的非线性关系,且饱和度指数值仅为1.01～1.10.经阳离子交换量校正后的饱和度指数值明显增大为1.56～1.65.利用CT扫描和扫描电镜(SEM)分析有助于研究岩石内部的微观结构、孔隙以及矿物的分布.

关键词: 低电阻率油层, 影响因素, 孔隙度, 渗透率, 毛细管压力, 扫描电镜, 计算机层析扫描