复杂孔隙结构砂岩储层岩电参数研究

On Archie's Electrical Parameters of Sandstone Reservoir with Complicated Pore Structures

含油岩石电阻率与饱和度关系的理论基础是经典阿尔奇公式,其应用效果主要取决于合适的岩电参数。复杂孔隙结构砂岩具有低孔隙度低渗透率、微孔、微裂隙发育、非均质性强等特点,其岩电参数特征在许多方面与常规储层存在显著差异。以鄂尔多斯盆地上古生界低渗透砂岩储层岩电实验资料为依据,研究了复杂孔隙结构对储层电学参数的影响,探讨了通过储层分类和采用可变m、n指数提高低渗透储层饱和度测井评价效果的方法。研究表明,渗透率1×10-3μm2、孔隙度12%对应储层的岩电特征是一个重要的分界点,孔隙度大于12%的储层岩电参数值与汉布尔公式很接近,小于12%的储层表现特殊;榆林气田山2石英砂岩n值接近于1是储层板状喉道发育、孔喉分选好的体现。给出了1口井的解释实例。

Archie formula is the classical theory that describes relationship between resistivity and water saturation（Sw）of hydrocarbon-bearing sandstone reservoir. Its application effect mainly depends on appropriate electrical parameters. Sandstone with complicated pore structures is charaterized by low porosity, low permeability, more microporosity ,more microfissure and great heterogeneity. Its electrical parameters are evidently different from conventional reservoirs. This paper, based on the core electricity experiment data of low permeability sandstone of Upper Palaeozoic in Eerduos basin, investigates the effects of complicated pore structures on electrical parameters, analyses the method to improve the precision of water saturation calculation through reservoir classification and using alterable m and n parameters. Study shows that 1×10^-3μm^2 permeability and 12% porosity are the important key point that distinguishes core electricity characters. The parameters are close to that of Humble formula when the porosity is higher than 12%, while the parameters are special when the porosity less than 12%. The parameter n of shan-2 quartz sand in Yulin gasfield, close to 1.0, shows the well growth of tabular throats and good sorting of pore throats. A ease study is given in this paper.