影响饱和度指数n的因素

The Factors Affecting Saturation Exponent, n

According to capillary theory, the factors affecting resistivity and saturation exponent, n, is analysed, and it is found that formation resistvity is a function of water viscosity, salt ion mobility, formation water resistivity and weighted average of water-bearing capillary bore radius to the fourth power. For oil-bearing rocks, the resistivity is also affected by the membrane thickness of absorbed water besides the above factors, in this case, the increase in resistivity results from the smaller bore diameter and the decrease in the number of capillary bores after waterflooding. The exponent, n, is a function of capillary bore diameter distribution index, D, and increases with permeabilily, and ranges from 1.0 to 2.0. For porous rocks, exponent, n, equals to 2. The results from capillary theory analysis is agree with practical data, but it is not applicable to heterogeneous media.