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.

In this paper, a series of Zn_xCe_1−xO₂ (x = 0.00, 0.05, 0.10, 0.15, and 0.20) nanoparticles were synthesized via an aqueous-phase coprecipitation method. The Zn_xCe_1−xO₂ nanoparticles were coated on honeycomb ceramics to prepare monolithic catalysts, and the catalytic activity of the monolithic catalysts was investigated for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol in a continuous tubular fixed-bed reactor. The as-prepared catalysts were fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption/desorption isotherms, H₂-temperature-programmed reduction (H₂-TPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and CO₂-temperature-programmed desorption (CO₂-TPD). The characterization results showed that doping Zn ions into the ceria lattice formed a fluorite-like solid solution and modified the structure and surface properties of the catalysts. Among all the monolithic Zn_xCe_1−xO₂ catalysts, the monolithic Zn_0.10Ce_0.90O₂ catalyst showed the highest catalytic activity with a methanol conversion of 20.5% with DMC selectivity of 82.1% at 160 °C and 2.4 MPa in the absence of any dehydrating agents. This superior catalytic activity was mainly attributed to a series of better properties, such as larger specific surface area (i.e. 179.9 m² g⁻¹), higher oxygen vacancy concentration, and the unique structure of the monolithic catalyst (e.g., removing by-product of water in time). This study provides a valuable design strategy for highly efficient direct synthesis of DMC using monolithic catalysts in the fixed-bed reactor.

Background: Despite the fact that a number of traditional shale inhibitors have been utilized widely in drilling operations, the same additive may be unfavorable for different drilling due to environmental protection requirements which limit scales of use. Hence, a series of polyammonium compounds was prepared from dimethylamine, epichlorohydrin, and melamine (DEM). Methods: To concentrate our efforts, we used both standard and extra methods to investigate the inhibitive properties of a melamine crosslinking agent using mud balls immersion tests, linear expansion measurements, laser particle distribution measurements, thermogravimetric analysis, and scanning electron microscopy. Results: The anti-swelling rate of DEM-8 reached up to 92.3% when its concentration reached 0.8%. DEM-8 has strong inhibitive capability to bentonite hydration swelling. DEM-8 can affect the bentonite particle size at a large scale. It may adsorb on the surface of clay through hydrogen bonds and electrostatic interaction by an anchoring effect and a hydrophobic effect. Conclusions: Compared with a blank solution, DEM-8 displays high inhibitive ability against the hydration and swelling of clay. The mud ball is more stable in DEM-8 solution and its swelling degree is very low compared with that of the control test. The inhibition mechanism of DEM-8 to shale can be deduced in that hydrogen bonding, ion exchange, and anchoring effect help to control the hydration and swelling.

In this work, a hydrophobically associative polymer (HAP) was mixed with β-cyclodextrin and epichlorohydrin polycondensate (β-CDP) in an aqueous solution to enhance the intermolecular interaction through host–guest inclusion between hydrophobes and cyclodextrins. Results showed that the host–guest interaction improved the thickening ability and viscoelasticity of the HAP solution and maintained its shear thinning behavior. The host–guest inclusion system demonstrated special viscosity–temperature curves and variable activation energy. Enhanced oil recovery (EOR) performance tests showed that the oil increment produced by the host–guest inclusion system was 5.5% and 9.3% higher than that produced by the HAP and the partially hydrolyzed polyacrylamide solution, respectively. Compared with pure HAP, β-CDP/HAP has a better comprehensive performance and is more attractive for EOR in high-temperature reservoirs.

The high-temperature stability and filtration property controlling of ultra-high-temperature water-based drilling fluids is a worldwide problem. To resolve this problem, a high-temperature-resistant quaternary copolymer (HTRTP) was synthesized based on molecular structure optimization design and monomer optimization. The physical and chemical properties were characterized by infrared spectroscopy, thermal weight, and spectrophotometry, and their temperature and salt resistance was evaluated in different drilling fluids, combined with adsorption, particle size analysis, and stability test. The results show that the thermal stability of HTRTP is very strong, and the initial temperature of thermal decomposition is above 320°C. The salt resistance of HTRTP is more than 162 g/L, and the calcium resistance is more than 5000 mg/L, which is equivalent to the foreign temperature-resistant polymer DCL-a, and is superior to the domestic metal ion viscosity increasing fluid loss agent PMHA-II for drilling fluids. It has excellent high-temperature resistance (245°C) and fluid loss reduction effect in fresh water base mud, fresh water weighted base mud, saturated brine base mud, and composite salt water base mud, which is better than foreign DCL-a (245°C) and domestic PMHA (220°C). The adsorption capacity of HTRTP on clay particles is large and firm, and the adsorption capacity changes little under the change of chemical environment and temperature. Both before and after HTRTP aging (245°C/16 h), the permeability of filter cake can be significantly reduced and its compressibility can be improved. By optimizing the particle size gradation of the drilling fluid and enhancing the colloid stability of the system, HTRTP can improve the filtration building capacity of the drilling fluid and reduce the filtration volume. The development of antithermal polymer provides a key treatment agent for the study of anti-high-temperature-resistant saline-based drilling fluid.