Regulation of polymerizable modification degree of nano-SiO2 and the effects on performance of composite microsphere for conformance control

Due to the superior performance caused by surface modification and combined effects, polymer/nano-SiO2 composites have been studied systematically for a long term and attracted increasing academic and industrial interests, especially in the petroleum engineering field. However, few works have been done on the mechanism that how the functional modification degree (MD) of nano-SiO2 influences on the properties of the composites. In this work, a series of 3-(methacrylyloxy)propyltrimethoxysilane (MPS) modified nano-SiO2 particles with different MDs were prepared and found to differ largely from each other in macroscopic properties. Then the effects of SiO2 MD on the physicochemical property and the enhanced oil recovery (EOR) capacity of the corresponding polymer/nano-SiO2 composite microspheres (PNSCMs) for the conformance control in oilfields were investigated in detail. The results clarified that by regulating the MD of nano-SiO2 encapsulated in PNSCMs, the swelling property, viscoelasticity, mechanical strength and dispersion stability were significantly improved. Compared with traditional chemical copolymer microspheres CPMs, PNSCMs exhibited better conformance control and EOR ability, which was further improved as SiO2 MD increased. The maximum oil recoveries of cores treated by PNSCMs were 76.14% and 52.45% in the experiment, and the EOR increased by 5.99% and 4.99% than those treated by CPMs, respectively, under homogeneous and heterogeneous conditions.