Polymer gel plugging is an effective method for gas mobility control in flue gas flooding reservoirs. However, the effect and mechanism of flue gas on the performance of polymer gels have rarely been reported. In this study, a polymer gel was prepared by cross-linking hydrolyzed polyacrylamide (HPAM) and resorcinol/ hexamethylenetetramine (HMTA) to illuminate the influencing mechanism of flue gas composition on gel. The gel rheological testing results showed that flue gas promoted gelation performance, whereas it seriously threatened gel long-term stability, especially at high pressure conditions. The influence of CO2 on the polymer gel had the characteristic of multiplicity. The hydrodynamic radius (Rh) and the initial viscosity of HPAM solution decreased in the presence of CO2. Nonetheless, the dissolved CO2 expedited the decomposition rate of HMTA into formaldehyde, which promoted the cross-linking process of the HPAM, leading to a shorter gelation time. Oxidation–reduction potential (ORP) tests and Fourier transform infrared spectroscopy (FTIR) analysis indicated that O2 played a leading role in the oxidative degradation of HPAM compared to CO2 and threatened the gel long-term stability at elevated gas pressures. To address the adverse effects caused by flue gas, it is highly desirable to develop polymer gels by adding oxygen scavengers or strengthening additives.
Chromium acetate-HPAM gel is developed to solve the gas channeling problem in low-permeability flue gas flooding reservoirs. Polyacrylamide with low molecular weight of 2 million is optimized as the main agent to construct an organic chromium gel system. The acid resistance performance and blocking capacity of the gel system are evaluated afterwards. It is revealed by the tests that acid components in flue gas have a severe impact on the gelation time, strength as well as long-term stability of the cross-linked gels. Rheological tests show that the gel system embodies with high elastic modulus in flue gas environment at 42°C, which ensures its favorable performance in core flooding tests. After gel application in cores, the permeability reduction can reach up to 99% and 97% separately while water flooding and flue gas flooding. The chromium acetate-HPAM gel exhibits perfect mobility control ability and possesses immense potential as regulating blocking system in low-permeability flue gas flooding reservoirs.
A highly site-selective palladium-catalyzed ortho-mono-aroyloxylation of O-aralkyl substituted acetoxime ethers via direct Csp2–H bond activation has been developed with simple exo-acetoxime as a directing group.
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