阿尔奇公式的适用条件分析及对策

摘要

Archie's formula is the foundation of sandstone reservoir using well logging data to calculate oil saturation. But in the argillaceous sandstone,low resistivity,and complex porosity reservoirs,the effect becomes worse. The main reason is that the applicable conditions of the Archie formula lacks clear understanding. Based on a large number of experimental data of rock electricity,this paper uses the method of function analysis to analyze the applicable conditions of Archie formula. The results show that the applicable condition of Archie formula is implied: under the same lithology and different pore rock, the rock electrical parameters a, b, m, n value should be exactly the same or approximate; electrical parameters of rocks with different sand a, b, m, n value, the greater the gap, the worse effect of using Archie formula. At the same time, the function formula of Archie formula can be well applied in shaly sandstone,low resistivity reservoir or complex pore reservoir. The difference is that the rock electrical parameters have obvious change compared with conventional sandstone reservoir. Because there is no better method to determine the a,b,m and n values of rock electrical parameters by point or by layer in logging interpretation, the unreliability of rock electrical parameters in interpretation is an important reason affecting the calculation accuracy of oil saturation. Therefore, it is an effective way to improve the coincidence rate of logging interpretation by using the corresponding rock electrical parameters in different layers of sandstone. The study points out the key problems of the current use of Archie formula, and puts forward different views on the application of the Archie formula in argillaceous sandstone and low resistivity reservoir,complex porosity of reservoir,which serves as a reference for the debate about relevant issues in recent years.%阿尔奇公式是砂岩储层利用测井资料计算含油饱和度的基础,但在泥质砂岩、低阻储层、复杂孔隙储层使用时效果变差,研究认为主要原因是对阿尔奇公式的适用条件认识不清.为此依据大量岩电实验数据,采用函数分析的方法,对阿尔奇公式适用条件进行了分析.结果表明,阿尔奇公式隐含的适用条件是:相同岩性、不同孔隙的岩样,其岩电参数a、b、m、n值应完全一样或大致接近;不同砂层的岩电参数a、b、m、n值差距越大,阿尔奇公式使用效果越差.同时,阿尔奇公式的函数关系式在泥质砂岩、低阻储层或复杂孔隙储层均能较好应用,区别在于与常规砂岩储层相比,岩电参数有明显变化.由于测井解释中逐点或逐层的岩电参数a、b、m、n值没有较好的确定方法,解释中所用岩电参数不可靠是影响含油饱和度计算精度的重要原因.所以,不同层砂岩使用相应的岩电参数,是提高测井解释符合率的有效途径.该研究指出了当前使用阿尔奇公式存在的关键问题,对阿尔奇公式在泥质砂岩、低阻储层、复杂孔隙储层的适用性提出了不同见解,对解决多年来围绕相关问题所进行的争论具有借鉴意义.