三维油藏流动电位数值模拟及油水前缘预测

根据流动电位产生的基本原理,建立三维油水两相流动条件下电场和渗流场的耦合数值模型并采用有限差分方法进行求解;以四分之一"五点法"井网为对象,模拟计算一注一采生产过程中井底的电位变化。结果表明:油水前缘的位置会出现电位的峰值,该峰值随注入水向生产井一侧移动,生产井底的电位会连续上升,当油水前缘距离生产井75 m时开始剧烈变化,因此对该效应的监测及分析能够实现油水前缘的远距离预测;注入水沿高渗透层的快速前进会引起电位异常,使高渗透层比低渗透层要高出5~15 mV,通过对该信号的强弱和随时间的变化规律的分析能够识别地层非均质性和注入水的不均匀推进,该方法具有成为新型动态监测手段的潜力。

3D numerical simulation of streaming potential in water-flooded reservoir for oil-water front prediction

Based on the fundamental principles of streaming potential of fluid flow in oil reservoirs, a 3D numerical model in coupling hydraulic and electrical flows with two phases (oil and water) was developed and solved by a finite differential method. A simplified model with one injector and one producer to simulate a quarter of a five point well pattern was studied, and the distribution of the streaming potential during water flooding was calculated using field and experimental data. The results show that the moving front of oil-water is in accordance with the peak of the streaming potential towards the production well, and the potential around the production wellbore increases gradually, but a sharp variation occurs when the oil-water front reaches to a certain range (i.e. about 75m from the producer wellbore). Therefore, this phenomenon can be used as an indication for the early prediction of the coming of injected water front. The encroachment of injected water along high permeability zones is remarkable in comparison with that in low permeability zones, and the subsequent difference in streaming potential is 5-15mV, which can be used to identify reservoir heterogeneity and non-uniform water front.