一种计算超低渗储层相对渗透率的新方法

相对渗透率曲线是油藏数值模拟的关键参数。超低渗透储层致密,喉道细小,孔隙结构非常复杂,在水驱油实验过程中,毛管压力作用和末端效应非常显著。在超低渗储层水驱油实验的基础上,首先应用传统的JBN方法(忽略毛管压力的影响)计算相对渗透率,发现其是不适用的。为了克服岩心末端效应的影响,应用X-ray CT扫描技术获得含水饱和度剖面数据;并结合两相饱和度剖面理论,推导了一种计算两相相对渗透率的新方法。结果表明:应用模型计算的相对渗透率曲线能够反映超低渗储层毛管压力大的特征。超低渗透岩心的水相渗透率起初上升很慢,随后快速升高;而油相渗透率下降迅速。研究成果对于超低渗储层两相相对渗透率的计算具有重要意义。

A New Method for the Calculation of Two-phase Relative Permeability in Ultra-low Permeability Reservoir

Relative permeability function is important for reservoir numerical simulation. In ultra-low permeability reservoir, the pores and throats are very small and the pore structure is very complex, leading to obvious capillary pressure effect and end effect in the process of water flooding experiment. The traditional JBN method (ignoring the capillary pressure) is not applicable to calculate the relative permeability of ultra-low permeability reservoir. In order to overcome the core end effect, X-ray CT technique was applied to obtain water saturation profile data. In this work, a new method for calculating the two-phase relative permeability was proposed. Results show that the relative permeability curves calculated by the proposed method can reflect the features of ultra-low permeability reservoir, the permeability of water phase rises slowly at first and then increases rapidly, while the permeability of oil phase declines rapidly. The research is of great benefit to the calculation of two-phase relative permeability in ultra-low permeability reservoir.