低孔低渗碎屑岩储集层双孔隙饱和度模型

Dual-porosity saturation model of low-porosity and low-permeability clastic reservoirs

低孔低渗储集层岩电关系存在大量的"非阿尔奇"现象,经典的阿尔奇模型在这类储集层的饱和度定量评价中存在一定不适用性。根据低孔低渗储集层孔隙结构特点,提出了一种新的考虑孔隙结构的双孔隙饱和度模型,即将岩石总的电阻视为自由水和微孔隙水两部分电阻的并联,综合考虑大孔隙与微孔隙对岩石电性的影响。利用该模型模拟岩样岩电关系,所得计算值同实测结果吻合很好。在中国东部和中部两种不同成因低孔低渗储集层评价中的应用效果表明,与阿尔奇模型相比,双孔模型同时考虑了岩性、物性、孔隙结构和含油性对电性的多重影响,因而利用其计算的含油饱和度更符合油藏的实际规律和岩石物理特征,更接近地层的真实含油情况。

Abundant non-Archie phenomena have been discovered in rock electrical property experiments of reservoirs with low-porosity and low-permeability,and the classical Archie model is not suitable for the oil saturation calculation in these reservoirs.Based on the pore structure characteristics of these reservoirs,a new dual-porosity saturation model considering the effect of pore structure is presented,namely,the total rock resistance is considered as the parallel resistance of free water resistance and micro-pore water resistance.Both the effects of large pores and micro-pores on rock electrical properties are considered in this model.The model is applied to rock samples to derive the theoretical litho-electric relations which are in good agreement with the experiment measurement.The applications to low-porosity and low-permeability reservoirs of different origins in the east and middle of China show that,compared to the Archie model,the new model considers the effects of rock lithology,physical property,pore structure and oiliness on electrical properties.Therefore,oil saturation resulted from the new model is in good accordance with the real regularity and petrophysical characteristics of reservoirs,and it is much closer to the real oil-bearing conditions.