M6断块中低孔隙度渗透率砂岩储层饱和度模型优选方法

通过M6断块19块中低孔隙度渗透率砂岩样品的岩电实验结果得出,地层因素和孔隙度总体表现出非阿尔奇关系的特征,直接沿用Archie公式计算含水饱和度不准确。在Archie公式的基础上,分析了岩电参数m、n的变化规律,当n为定值时,认为m是影响饱和度精度的关键参数,在实验结果中归纳出m受无效导电孔隙(有效孔隙与有效导电孔隙的差值)的影响较大,提出利用无效孔隙求取m,进而提高Archie公式求取饱和度的精度。基于等效岩石组分理论对岩石导电性的影响,利用遗传算法求解方程组中每块样品的比例系数k和临界饱和度Swc,总结出变化规律,依据EREM模型采用迭代法得到相应的饱和度。通过对比3种方法求取的结果,结合试油层段的束缚水饱和度,表明EREM模型得到的含水饱和度最接近实际地层情况,而变参数Archie公式计算的结果次之。研究认为EREM模型更适合于中低孔隙度渗透率砂岩储层的饱和度计算。

Saturation Model Optimizing Method for Medium-low Porosity and Permeability Sandstone Reservoir in M6 Fault Block

Formation factor and porosity can not characterize Archie relationship overall by the study of core-electricity experiment results of 19 medium-low porosity and permeability sandstone reservoir core samples in M6 fault block,that's why water saturation calculation is not accurate by using Archie relationship directly.Therefore,this paper proposes corresponding solution ideas from two aspects.First,based on Archie formula,the change laws of rock electricity parameter n and n are analyzed and m is the key parameter which affects the accuracy of saturation,cementation index m is highly affected by invalid conductive pore (difference of effective porosity and effective conductive pore) by experiment results study as well,then m is calculated by invalid pore.The accuracy of Archie formula to calculate the saturation then is improved.Second,Based on the theory of equivalent rock composition effect on rock conductivity,proportion coefficient k and the critical saturation Swc of every core sample in the equation set are calculated by genetic algorithm,then saturation can be calculated by using iteration method according to EREM model.Combining with irreducible water saturation of testing interval and the comparing results of the three methods,formation water saturation calculated by EREM model more closer to the actual situation than the results of variable parameters of Archie formula.EREM model is more suitable for calculation of saturation of medium-low porosity and permeability sandstone reservoir.