浅谈阿尔奇公式中饱和度指数(n)的测定方法

The Measuring Methods for the Saturation Exponent(n) in Archie Equation

阿尔奇公式中饱和度指数n值的测定有多种方法。介绍了油驱法、离心法、气驱法、隔板法和增水法测定储集层饱和度指数的基本方法。油驱法用模拟油驱替100%含水的储集层岩样以测定储集层电阻增大率与含水饱和度关系;离心法是利用离心力克服储集层岩样的毛细管力,对中高孔隙度渗透率储层很有效;气驱法是模拟气藏形成的过程,用气体逐渐驱替储集层岩样中原有的水,在岩样不同的含水饱和度条件下测定电阻率;隔板法是用半渗透隔板在一定的压力下通过的润湿相溶液确定饱和度指数;增水法是利用储集层岩样的毛细管力达到不同的含水饱和度值确定储集层的饱和度指数。这5种方法在鄂尔多斯盆地砂岩和碳酸盐岩储集层进行了应用,结果显示该盆地储集层的饱和度指数呈非常复杂的特性,应根据储集层的物理性质,选择合适的方法测定储集层的饱和度指数。

In Archie equation, there are many ways to measure the saturation exponent （n）, among which the oil driving method, centrifuging method, gas driving method, baffle method and water increasing method are common and effective. The oil driving method is to measure relation between the resistivity index and water saturation in the reservoir with modeling oil driving the reservoir samples having 100 percent of water. The centrifuging method is to overcome the capillary force with centrifugal force, so it is effective in medium-high porosity and permeability reservoir. The gas driving method is to model forming process of the reservoir and gradually drive water in the reservoir samples, and measure the resistivity of the samples with different water saturations. The baffling method means that the wetting phase fluids may pass through the semi-permeable baffle but the non-wetting phase fluids may not at a certain pressure. The water increment method is to determine the saturation exponent （n） by using the capillary force in the reservoir samples to obtain different water saturations. Measurements of the saturation exponent of the sand stones and carbonates in grdos basin with the five methods indicate the saturation exponent of the reservoirs in grdos basin is very complex. And we should select the right method to measure the saturation exponent according to the physical property of the reservoir.