基于分形理论的束缚水饱和度应力敏感性定量表征

Quantitative Characterization of Stress Sensitivity of Irreducible Water Saturation Based on Fractal Theory

以分形理论和油层物理学为基础,假设岩石变形前后单位孔隙表面上所吸附的束缚水量保持不变,推导建立了束缚水饱和度随地层压力下降发生变化的理论关系式,定量分析了应力敏感和微观孔隙结构非均质性对束缚水饱和度的影响。随着地层压力的下降,束缚水饱和度增加,束缚水体积减少。束缚水饱和度的增加会导致油相的有效渗流空间减少,从而引起孔隙中油、水赖以流动的通道变窄,降低油相的有效渗透率,产生了启动压力梯度等现象,对流体的流动规律和产能计算产生了影响。

Based on fractal theory and reservoir physics,and assuming that the amount of irreducible water adsorbed on the unit pore surface remains unchanged before and after rock deformation,the theoretical relationship on the change of irreducible water saturation with the drop of formation pressure was deduced and established,and the influences of stress sensitivity and microscopic pore structure heterogeneity on the irreducible water saturation were quantitatively analyzed.As the formation pressure decreases,the irreducible water saturation increases and the irreducible water volume decreases.The increase in irreducible water saturation will lead to the reduction in effective flow space for oil phase,which will narrow down the flow channels for oil and water in the pores,reduce the effective permeability of the oil phase,generate the threshold pressure gradient,and finally impact the fluid flow laws and capacity calculations.