低渗透油藏纳米微球调驱剂封堵性评价新方法

New method for plugging performance evaluation of polymeric nanospheres in low permeability reservoir

纳米聚合物微球具有初始粒径小、黏度低、吸水缓膨等良好的深部调驱性能。基于渗流力学原理,以及渗透率与岩石学参数的数学关系,明确了微球在地层聚集,增大比表面、降低渗透率的调驱机理,建立了微球调驱封堵率的计算方法,并对王窑低渗透油藏微球调驱封堵率进行了计算与分析。研究结果表明:微球粒径越小,质量浓度越高,注入地层后渗透率降低幅度越大,封堵性能越强;小粒径微球聚集封堵、大粒径微球单个卡堵大孔喉,在地层协同作用下达到逐级调驱的目的;填砂管实验结果与理论封堵率趋势一致,从端面效应分析了填砂管封堵率偏高的原因,对低渗透油藏纳米微球调驱机理探索及调驱工程设计具有较好的指导意义。

With small initial particle size, low viscosity and slow water swelling, polymeric nanospheres have good in-depth profile control performance. Based on principles of seepage mechanics and mathematical relationship between permeability and petrological parameters, the profile control mechanism of nanospheres with accumulating nanosphere particles in formation, increasing specific surface and reducing permeability, is clarified. Calculation method of nanospheres plugging rate was established and plugging rate of nanospheres was calculated in Wangyao low permeability reservoir. Results show that the smaller the particle size is, the higher the mass concentration is; the greater the reduction scope of permeability is, the better the plugging performance is. A large number of small diameter nanospheres accumulate and plug pore throat, some single big diameter nanospheres plug the dominant channel of waterflood. The synergistic action achieved the purpose of in-depth profile control of nanospheres by both small nanospheres and big nanospheres. The experimental result of sand filled pipe is in accordance with the theoretical plugging rate, and the reason for high plugging rate of sand filled pipe was analyzed from inlet surface effect, which has better directive significance to exploring the mechanism of nanospheres profile control in low permeability reservoir and its engineering design.