多薄层特低渗透滩坝砂油藏CO_(2)驱层系组合优化

Optimization of layer combination of CO_(2) flooding in multi-thin-layer beach-bar sandstone reservoirs with extra-low permeability

为了解决特低渗透滩坝砂油藏CO2驱纵向驱替不均衡的问题,利用油藏数值模拟方法分析了储层渗透率、地层原油黏度、含油饱和度和油层厚度等因素对层系组合的影响,并利用正交试验方法确定各因素的影响程度从大至小依次为:原油黏度、含油饱和度、储层渗透率、油层厚度。通过公式推导和油藏数值模拟方法,建立了考虑含油饱和度、原油黏度和储层渗透率等3个主控因素以及启动压力梯度和压裂影响的综合有效流度作为层系组合的表征指标。基于油藏数值模拟技术,确定了不同注采压差下的综合有效流度的界限值,随着注采压差的增大,界限值逐渐减小。依据各油层的综合有效流度值,采用K-means聚类方法实现层系组合自动划分。将研究成果应用到胜利油区正理庄油田高89区沙四段,结果显示将层系划分为3套时的采出程度提高了2.25%。

To avoid uneven vertical displacement of CO2 flooding in beach-bar sandstone reservoirs with extra-low permea⁃bility,we analyze the influence of reservoir permeability,crude oil viscosity,oil saturation,and oil layer thickness on layer combination by the numerical simulation.The orthogonal test method is used to determine their degrees of influence in de⁃scending order:crude oil viscosity,oil saturation,reservoir permeability,and oil layer thickness.Through formula deriva⁃tion and numerical simulation of reservoirs,comprehensive effective fluidity that involves oil saturation,crude oil viscosity,and reservoir permeability,as well as starting pressure gradient and fracturing,is proposed to characterize layer combina⁃tion.The limits of comprehensive effective fluidity under various injection-production pressure differences are determined with the numerical simulation technology for reservoirs.As the injection-production pressure difference increases,the limit gradually decreases.According to the comprehensive effective fluidity of each oil layer,the K-means clustering algorithm is used for the automatic division of layer combination.The research results are applied to the Es4 in Block Gao89 of Zhengl⁃izhuang Oilfield,showing that the recovery is raised by 2.25%when the layers are divided into three schemes.