基于J函数毛管力的数值建模在低渗油气藏中的应用

Application of numerical modeling of capillary pressure based on J function in low permeability reservoirs

低渗油气藏的含油气饱和度分布与储层性质、压力系统以及岩石的微观结构有关。而由于储层性质存在的毛管力,对渗流起着不容忽视的作用。从毛管力出发,采用J函数平均毛管力,消除油气藏物性等因素对其曲线的影响。根据渗流力学、流体力学、油藏数值模拟,建立了J函数平均毛管力饱和度模型,对比分析了有无毛管力对驱替效果及油气水垂向分布的影响,同时研究了不同润湿程度的水驱油效果。结果表明:(1)毛管力是亲水油藏的驱油动力,有利于油气的流动和采出;(2)毛管力作用可使油气水在垂向上分布更加均匀;(3)注水驱替非均质地层时,地层的润湿性决定分流量。处于弱水湿状态的岩石,能获得最大的水驱油采出程度。

The distribution of oil and gas saturation of low permeability oil and gas reservoirs is influenced by reservoir properties, pressure system and the microstructure of rock. However, the capillary pressure caused by properties of the reservoirs is very important to the seepage. Based on the capillary pressure, the average capillary pressure solved by the J function to eliminate the influence of factors such as the physical properties of the oil and gas reservoir on its curve. According to the seepage mechanics, fluid mechanics and reservoir numerical simulation, the saturation model of J function and the average capillary pressure was established. The effects of the capillary pressure on the water flooding is analyzed, the capillary pressure how to influences the vertical equilibrium of oil-gas-water is studied, and the effect of water flooding with different wetting degrees of rock is also studied.（1）The capillary pressure is the driving force of the water-wet reservoir, which is conducive to the flow and production of oil and gas.（2）The capillary pressure can make the oil, gas and water more vertically well-distributed.（3）When water flooding drives a heterogeneous low-permeability zone, the wettability of the formation determines the water allocation of different flow paths and water flooding oil recovery will get the highest with the rock in weak-water wet state.