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-SiO 2 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-SiO 2 influences on the properties of the composites. In this work, a series of 3-(methacrylyloxy)propyltrimethoxysilane (MPS) modified nano-SiO 2 particles with different MD s were prepared and found to differ largely from each other in macroscopic properties . Then the effects of SiO 2 MD on the physicochemical property and the enhanced oil recovery (EOR) capacity of the corresponding polymer/nano-SiO 2 composite microspheres (PNSCMs) for the conformance control in oilfields were investigated in detail. The results clarified that by regulating the MD of nano-SiO 2 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 SiO 2 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.