纳米二氧化硅改性聚合物的油藏适用性评价与微观驱油效果研究

为增强驱油用聚合物的油藏适用性，进一步提高原油采收率，评价了一种具有纳米颗粒/聚合物复合结构的纳米二氧化硅改性聚合物的溶液特性及其驱油效果。在温度90 ℃、矿化度20 000 mg/L条件下，利用Brookfiled黏度计和安东帕高温高压流变仪MCR，评价了纳米二氧化硅改性聚合物与2种未改性聚合物溶液性能的差异；通过岩心驱替试验，分析了上述3种聚合物的驱油效果；通过微观驱油试验，观察了孔隙模型注入3种聚合物前后原油的分布情况。试验得出，由于纳米二氧化硅改性聚合物分子间相互作用更强，分子间网络具有更好的形变恢复能力，其增黏、抗温、抗盐、抗剪切和抗老化等性能与其他2种聚合物相比均有大幅提高。微观驱油效果研究发现，纳米二氧化硅改性聚合物可将采收率提高21百分点，高于支化聚合物（13百分点）和线型聚合物（9百分点）。微观驱油效果研究结果表明，纳米二氧化硅改性聚合物可以改善多孔介质的非均质性，能大幅减少多孔介质中孤岛状油珠和长条状剩余油的数量，显著降低残余油饱和度。 

Research on Reservoir Applicability Evaluation and Micro Oil Flooding Effect of a Nano-Silica Modified Polymer

The solution characteristics and oil displacement effect of a nano-silica modified polymer with nanoparticle-polymer composites were evaluated to enhance the applicability of oil displacement polymers in reservoirs and further improve oil recovery. The performance differences between different polymer solutions, including a nano-silica modified polymer and two unmodified polymers, were evaluated by Brookfield viscometer and HTHP Anton Paar rheometer at 90 °C and 20,000 mg/L of salinity. The oil displacement effects of above polymers were analyzed by core flooding experiments. The distributions of crude oil in the pore model before and after flooding with three kinds of polymers were observed through micro oil flooding experiments. The experimental results showed that the molecular network had better performance in deformation recovery because the interaction between the molecules of nano-silica modified polymer was stronger. Compared with the other two polymers, the nano-silica modified polymer presented large improvement in increasing viscosity, improving temperature resistance, salt resistance, enhancing shearing endurance and aging stability, and increased the oil recovery ratio by 21 percentage points, which was greater than that of branched polymer (13 percentage points) and that of linear polymer (9 percentage points) respectively. So, the nano-silica modified polymer can effectively alleviate the heterogeneity of porous media, greatly reduce the number of island-like oil beads and long strip-like remaining oil in the porous media, and significantly decrease the saturation of residual oil.