合采井层间干扰现象数学模拟研究

Mathematical Simulation Study on Interlayer Interference in Commingled Production

海上油田多为大段合采,层间干扰现象较为严重,为了正确评价这一现象,基于渗流力学理论,建立了考虑层数、厚度、渗透率、孔隙度、黏度、地层压力、供给半径和相渗数据等因素的层间干扰评价数学模型,模型考虑了层间非均质性、启动压力梯度、井筒连通、以及液量转移4个方面的层间干扰机理。利用数学模型,计算了实际井合采时的各层产能和全井产能、分采时的各层产能和全井产能以及层间干扰系数,对合采和分采条件下的产能进行分析。研究结果表明,渗透率级差、测试工作制度、所处含水阶段、静压及其他,对层间干扰的贡献比例分别为50%、25%、15%、10%。层间干扰主要受层间非均质性的控制,在进行层系组合时,若渗透率级差小于4,则可保证层间干扰系数小于0.6;若渗透率级差小于10,则可保证层间干扰系数小于0.6。

Offshore oil fields usually adopt a large-interval commingled production strategy. Interlayer interference is relatively serious. To evaluate this phenomenon correctly, based on the theory of seepage mechanics, an interlayer interference evaluation numerical model considering the number of layers, thickness, permeability, porosity, viscosity, formation pressure, supply radius, and so on, was established. The model considered four aspects of the interlayer interference mechanism, including the interlayer heterogeneity, initial pressure gradient, wellbore connectivity, and liquid transfer. Based on the mathematical model,the productivity of each layer and the entire well during commingled production, the productivity of each layer and the entire well during separate production, and the interlayer interference coefficient were calculated. The productivity under the conditions of commingled and separate production was analyzed. The results show that the contributions of the permeability difference ratio,test operation procedures, water saturation stage, hydrostatic pressure, and other parameters to the interlayer interference were50%, 25%, 15%, and 10%, respectively. Interlayer interference is mainly controlled by interlayer heterogeneity. During the commingling of multiple layers, if the permeability ratio is less than 4, the interlayer interference coefficient can be guaranteed to be less than 0.6. If the permeability ratio is less than 10, the interference coefficient can be guaranteed to be less than 0.6.