低渗透油藏近井地带单井渗流模型研究

Near-wellbore Percolation Model Used in Low Permeability Reservoirs

针对低渗油藏近井地带压力变化幅度大的特点,以试验结果为基础,建立了考虑储层物性随地层有效应力变化的单井渗流数学模型,给出了油水两相流动下的弹性和弹塑性储层的数值解计算公式,以及弹性储层的产量和井底流压解析表达式。考虑井底附近的渗流特点,对径向网格采用径向等对数划分的方法进行了处理。最后,以单井为对象,应用建立的数学模型研究了降压开发条件下,渗透率、油层厚度、平均地层压力、形变因子等储层参数变化时对油井产能的影响规律。结果表明,岩石的渗透率、形变因子和油层厚度对单位压差下的日产液量影响大,是主要的影响因素。

In consideration of the characteristics of big pressure changes in near wellbore area of low permeability reservoirs, based on experimental result, a single well percolation mathematical model that the reservoir physical property changed with effective stress was established, equations were given for calculating the elastics and elastoplastic reservoirs under the condition of oil and water flow and an analytical equation was also given for calculating the reservoir production and bottom-hole flowing pressure. In combination with the percolation characteristics in near bottom-hole area, radical grid was treated with logarithmic method. Based on single well process, the influence of reservoir parameter changes, such as permeability, reservoir thickness, average formation pressure, deformation factors on well productivity were studied by using the model under the depressure condition. The result shows that the major influence factors include rock permeability, its deformation factors and reservoir thickness, by which big influence is induced on daily fluid production output under unit pressure difference.