【摘要】 为了提高中低渗油藏的采收率，采用自由基聚合反应合成了一种以改性纳米SiO₂为核、聚丙烯酰胺为亲水支链的改性纳米SiO₂超支化共聚物（MSHP）．通过一系列的实验对MSHPs的结构与流变性能进行了表征，结果表明，MSHPs具有良好的稳定性、平均粒径小，为210 nm，并具有均匀的网状交联结构；使用幂律方程对不同条件下MSHPs的流变曲线进行拟合，质量浓度提高，K值增大，溶液的黏度增大；对于质量浓度为1 000 mg/L的聚合物溶液，温度提高至75℃，K值从15.510降低至8.915，增黏效果下降；而矿化度提高后，溶液表观黏度降低，高剪切速率下，出现剪切变稠现象．油滴剥离与岩心驱替实验表明：相同浓度条件下的SDS溶液加入1 000 mg/L的MSHPs后，油膜剥离速度显著提高；一次水驱含水率为98%后注入0.5PV的MSHPs和后续水驱后，可进一步提高中低渗岩心的采收率分别为12.1%和14.2%.更多还原

【Abstract】 A modified nano-SiO₂ hyperbranched copolymer（MSHP）with modified nano-SiO₂ and polyacrylamide as the core and hydrophilic branch chain,respectively,was synthesized through a free radical polymerization reaction.This study aimed to improve oil recovery in medium-and low-permeability reservoirs. The structure and rheological properties of MSHPs were characterized through various experiments,which showed that MSHPs have good stability,a small average particle size of 210 nm,and a uniform reticular cross-linked structure. The power law equation was used to fit the rheological curves of MSHPs under different conditions:the mass concentration,K value,and viscosity of the solution were all increased. For the polymer solution with a mass concentration of1 000 mg/L,its K value decreased from 15.510 to 8.915 when temperature was increased to 75 ℃,whereas the increasing effect of viscosity was reduced. As salinity increased,the apparent viscosity of the solution decreased,and shear thickening occurred at high shear rates. Results of oil-drop stripping and core flooding experiments indicate that the rate of oil-film stripping significantly increased by adding 1 000 mg/L of MSHPs to SDS solution under the same concentration conditions. After a 98% water cut after preliminary water flooding,0.5PV MSHPs solution flooding and extended water flooding could further improve the recovery of medium-and low-permeability cores by 12.1% and 14.2%,respectively.更多还原