改性纳米SiO_(2)超支化共聚物在中低渗油藏提高采收率的性能研究

Enhanced Oil Recovery Performance of Modified Nano-SiO_(2) Hyperbranched Copolymers in Medium-and Low-Permeability Reservoirs

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SiO_(2)为核、聚丙烯酰胺为亲水支链的改性纳米SiO_(2)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1000 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1000 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%.

A modified nano-SiO_(2)hyperbranched copolymer(MSHP)with modified nano-SiO_(2) 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 of 1000mg/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 1000 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.