A novel hybrid hyperbranched nanowire CNTs for enhancing oil recovery through increasing viscoelasticity and high-viscous emulsions to compensate reservoir heterogeneity

Polymer flooding was one of the most cost-effective methods for enhanced oil recovery (EOR). It was the key for enhancing oil recovery that studying novel polymer could cope with harsh reservoir conditions. In this work, a hyperbranched nanowire (O-20 @PAM@CNTs) for polymer flooding was synthesized by in situ polymerization with monomers and hybrid carbon nanotubes (CNTs). FT-IR, 1H NMR, TEM, gel permeation chromatograph (GPC) and rheometer were used to characterize the composition, micro-morphology, MWD (molecular weight distribution) and rheological properties of O-20 @PAM and O-20 @PAM@CNTs. Compared with O-20 @PAM, O-20 @PAM@CNTs showed excellent viscosification, temperature resistance, anti-shear and viscoelastic properties. The hyperbranched nanowire had the best performance with the content of hybrid CNTs of 0.2% w/w and which molecular weight (741999) was about half that of O-20 @PAM (1330629). Enhanced performance of the O-20 @PAM@CNTs could be attributed to the hybrid CNTs provided polymer a hyperbranched structure to build more compact and complex network and boost the association between polymer chains. Besides, the fatty alcohol polyoxyethylene ether(O-20) on the chains of O-20 @PAM@CNTs raised the viscosity of flooding liquid by emulsification and that partly compensated the heterogeneity of the core, thus improved the displacement ef-ficiency markedly. Core Flooding Experiments shown that 0.3 times of pore volume O-20 @PAM@CNTs-0.2 increased oil recovery by 17.5% contrasting only 11.6% for 0.4 times of pore volume O-20 @PAM, in the same solution concentration (2000 ppm). O-20 @PAM@CNTs had more obvious advantage in performance and more economical than O-20 @PAM, which indicated a better application of O-20 @PAM@CNTs in EOR.

Automated summary

Polymer flooding is a cost-effective method for enhanced oil recovery. In this study, a hyperbranched nanowire (O-20 @PAM@CNTs) was successfully synthesized for polymer flooding, showing excellent viscosification and temperature resistance. The hybrid carbon nanotubes (CNTs) in O-20 @PAM@CNTs provided a hyperbranched structure and improved the association between polymer chains. Core flooding experiments demonstrated that O-20 @PAM@CNTs enhanced oil recovery more effectively than O-20 @PAM, indicating its better application in enhanced oil recovery.