摘要
本文综述了润湿性对岩石电阻率和阿尔奇饱和度指数以及地层因素的影响，这些参数是利用电测井资料评价含油饱和度的重要参数．润湿性影响流体在孔隙中的微观分布，因而影响岩石的电阻率．阿尔奇饱和度指数ｎ在水湿地层和清洗过的岩心中，一般大约为２，在保持为原始状态、非水湿的岩心及地层中，通常大于２，在低含水饱和度的均匀油湿岩心中，ｎ可以达到１０或更大．由于在油湿岩心中，当含水饱和度低时，一部分水被不导电的油圈闭起来或被分离成树枝状，使其对电的传导没有贡献，因此，在油湿岩心中，ｎ值较高．含水饱和度指数ｎ是润湿性的函数，对一给定岩石，润湿性指数与饱和度指数存在一线性关系，直线的斜率与岩石特性有关．若测量ｎ时用清洗过的水湿岩心，而在储层中实际上是油湿的，那么测井求出的含水饱和度将偏小．目前，关于润湿性对地层因素的影响还无一致的认识．
This paper reviews the effects of wettability on rock electrical resistivity and Archie saturation exponent,as well as the formation factor. These parameters are important in estimation of the oil saturation of a formation by use of resistivity data obtained from well logging. Because wettability affects the microscopic distribution of fluids in pores, it affects electrical resistivity of a rock. Generally,the Archie saturation exponent n has a value of about 2 in water-wet formations and cleaned cores. In native state,non-water-wet formations and cores,n is generally larger than 2. It can reach a value of 10 or more with low water saturation in uniformly oil-wet cores. The exponent is higher in oil-wet cores at low saturations because some of the brine is trapped by oil or isolated in dendritic fingers where it is unable to contribute to electrical conductivity. The Archie saturation exponent is a function of wettability index. A linear relationship exists between the wettability index and the saturation exponent for a given rock. The slope of the line is a function of the petrophysical properties of the rock. If cleaned water-wet cores are used to determine n and the actual reservoir is oil-wet,the water saturation will be underestimated from resistivity curve. No definite conclusions about the effects of wettability on the formation factor can be drawn.
出处
《地球物理学进展》
CSCD
1998年第1期60-72,共13页
Progress in Geophysics
基金
中国石油天然气总公司"九五"科技攻关项目
关键词
润湿性
电阻率
含水饱和度指数
岩石
电性
Wettability,Electrical Resistivity,Water Saturation Exponent,Resistivity Index
