油气储层低频界面极化效应数值模型

基于储层岩石孔隙毛管模型，文中推导了储层宏观物性参数与微观孔隙流体导电性质和介电性质的定量关系，从而构建了一种定量描述储层岩石低频界面极化效应的等效电路模型。相对于传统的Cole-Cole等效电路模型，文中的等效电路模型参数具有更明确的物理含义，更适用于定量表征储层岩石低频界面极化效应。利用该等效电路模型分别对盐水饱和岩样及含油岩样低频界面极化效应进行了数值模拟，分析了储层岩石孔喉比、矿化度及含水饱和度等因素对虚部电阻率频散特征的影响。模拟结果表明，虚部电阻率极小值的模值与孔喉比、矿化度及含水饱和度均呈指数关系，虚部电阻率极小值的模值随孔喉比增大而增大，随矿化度和含水饱和度增大而减小。数值模拟结果为利用岩石低频界面极化效应对储层含油气性进行定量评价提供了理论基础和模型基础。

Numerical simulation of polarization effect in low-frequency interface of oil-gas reservoirs

Based on the pore capillary model of reservoir rock, this paper constructs the quantitative relationship between the macroscopic physical parameters of reservoirs and the conductivity and dielectric properties of microscopic pore fluids as well as an equivalent circuit model to quantitatively describe the polarization effect of low-frequency interface of reservoir rock. Compared with those of the traditional Cole-Cole equivalent circuit model, the parameters of the proposed equivalent circuit model show more explicit physical meaning and are more suitable for quantitatively characterizing the polarization effect of the low-frequency interface of the reservoir rock. The proposed equivalent circuit model is used to simulate the polarization effect of the low-frequency interface of rock samples saturated with saline water and oil-bearing rock samples, respectively, and the influence of pore-throat ratio, salinity, and water saturation of reservoir rock on resistivity dispersion of imaginary part is analyzed. The simulation results show that the modulus of the imaginary resistivity minimum is exponentially related to pore-throat ratio, salinity, and water saturation. Specifically, it increases as the pore-throat ratio improves and decreases as the salinity and water saturation rise. The numerical simulation results provide a theoretical and model basis for quantitatively evaluating the oil and gas in reservoirs by using the polarization effect of low-frequency rock interface.