Abstract
To improve oil recovery significantly in low-mid permeability reservoirs, a novel modified nano-SiO2 hyperbranched copolymer (HPBS), consisting of polyacrylamide as hydrophilic branched chains and modified nano-SiO2 as the core, was synthesized via an in situ free radical polymerization reaction. The structure and properties of the hyperbranched copolymer were characterized through a range of experiments, which showed that HBPS copolymers have better stability and enhanced oil recovery (EOR) capacity and also smaller hydrodynamic radius in comparison with hydrolyzed polyacrylamide (HPAM). The flooding experiments indicated that when a 1000 mg/L HPBS solution was injected, the resistance factor (RF) and residual resistance factor (RRF) increased after the injection. Following a 98% water cut after preliminary water flooding, 0.3 pore volume (PV) and 1000 mg/L HPBS solution flooding and extended water flooding (EWF) can further increase the oil recovery by 18.74% in comparison with 8.12% oil recovery when using HPAM. In this study, one can recognize that polymer flooding would be applicable in low-mid permeability reservoirs.
Highlights
The exploration and exploitation of unconventional resources is an inevitability due to the pace and trend of the development of the economy
For the reasons stated above, this research aimed to synthesize a hyperbranched copolymer based on modified nano-SiO2 for enhanced oil recovery in low-mid permeability reservoirs
All of these findings confirmed the existence of KH540 and maleic anhydride (MA) on the surface of nano-SiO2
Summary
The exploration and exploitation of unconventional resources is an inevitability due to the pace and trend of the development of the economy. These types of unconventional reservoirs possess a plethora of distinctive features, which include small pore throats, high specific surface area, severe heterogeneity and presence of low viscosity crude oil [5,6,7]. For these reasons, some researchers have studied gas and water injection to restore reservoir energy for enhanced oil recovery (EOR). Jakobsson [8] found that deep
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