Synthesis, Characterization, and Properties of a Novel Hyperbranched Polymers with Polyacrylamide Side Chains

A novel hyperbranched polymer with polyacrylamide side chains (HAPAM) was synthesized by aqueous solution polymerization using acrylic acid, acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, hydrophobic monomer of dimethyl octadecyl ammonium chloride, and the homemade skeleton monomer of modified-M2.0 as raw materials and (NH4)2S2O8-NaHSO3 as initiator. The molecular structure, functional groups, and surface morphology of HAPAM were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, and scanning electron microscopy. It was found that the performance of HAPAM solution was higher than that of ordinary polyacrylamide solution in terms of thickening ability, shearing resistance, thermal endurance, salt-resistance, resistance-coefficient and residual-resistance-coefficient, ability to reduce interfacial tension between polymer solution and crude oil, and oil-displacement-efficiency. In particular, the enhanced oil recovery of the HAPAM solution was 13.03%, and the improvement of shearing resistance and immunity to chromatographic separation were simultaneously achieved by the HAPAM solution. These results indicate that the successful synthesis of the novel HAPAM opens a promising strategy for developing new high-performance oil-displacing polymers.

Synthesis and Solution Properties of a Novel Hyperbranched Polymer Based on Chitosan for Enhanced Oil Recovery

A new type of chitosan-modified hyperbranched polymer (named HPDACS) was synthesized through the free-radical polymerization of surface-modified chitosan with acrylic acid (AA) and acrylamide (AM) to achieve an enhanced oil recovery. The optimal polymerization conditions of HPDACS were explored and its structure was characterized by Fourier-transform infrared spectroscopy, hydrogen nuclear magnetic resonance, and environmental scanning electron microscopy. The solution properties of HPDACS in ultrapure water and simulated brine were deeply studied and then compared with those of partially hydrolyzed polyacrylamide (HPAM) and a dendritic polymer named HPDA. The experimental results showed that HPDACS has a good thickening ability, temperature resistance, and salt resistance. Its viscosity retention rate exceeded 79.49% after 90 days of aging, thus meeting the performance requirements of polymer flooding. After mechanical shearing, the viscosity retention rates of HPDACS in ultrapure water and simulated brine were higher than those of HPAM and HPDA, indicating its excellent shear resistance and good viscoelasticity. Following a 95% water cut after preliminary water flooding, 0.3 pore volume (PV) and 1500 mg/L HPDACS solution flooding and extended water flooding could further increase the oil recovery by 19.20%, which was higher than that by HPAM at 10.65% and HPDA at 13.72%. This finding indicates that HPDACS has great potential for oil displacement.

CO2/N2-Responsive Nanoparticles for Enhanced Oil Recovery During CO2 Flooding

During CO₂ flooding, serious gas channeling occurs in ultra-low permeability reservoirs due to the high mobility of CO₂. The chief end of this work was to research the application of responsive nanoparticles for mobility control to enhance oil recovery. Responsive nanoparticles were developed based on the modification of nano-silica (SiO₂) by 3-aminopropyltrimethoxysilane (KH540) via the Eschweiler-Clark reaction. The proof of concept for responsive nanoparticles was investigated by FT-IR, ¹H-NMR, TEM, DLS, CO₂/N₂ response, wettability, plugging performance, and core flooding experiments. The results indicated that responsive nanoparticles exhibited a good response to control nanoparticle dispersity due to electrostatic interaction. Subsequently, responsive nanoparticles showed a better plugging capacity of 93.3% to control CO₂ mobility, and more than 26% of the original oil was recovered. Moreover, the proposed responsive nanoparticles could revert oil-wet surfaces to water-wet, depending on surface adsorption to remove the oil from the surface of the rocks. The results of this work indicated that responsive nanoparticles might have potential applications for improved oil recovery in ultra-low permeability reservoirs.

Feasibility Study of Applying Modified Nano-SiO2 Hyperbranched Copolymers for Enhanced Oil Recovery in Low-Mid Permeability Reservoirs

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.

Design and characterization of a microbial self-healing gel for enhanced oil recovery

Due to the heterogeneity of rock layers, the poor volumetric sweep efficiency of water and an invalid cycle have emerged as major problems in crude oil production.

Preparation of polyacrylamide microspheres with core–shell structure via surface-initiated atom transfer radical polymerization

Well defined core–shell microspheres were prepared by surface-initiated atom transfer radical polymerization with pre-crosslinked polyacrylamide as the core and non-crosslinked polyacrylamide as the shell.