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To investigate the CO2 corrosion of tubing in CO2 injection for production wells, the corrosion process is divided into four stages. Then the corrosive components, liquid production, water cut, wellhead temperature and production pressure difference at each stage are obtained. Based on these and in consideration of the changes in parameters, the prediction method for corrosion rate of tubing in CO2 flooding well is studied. Finally, the corrosion rate of the tubing in the example well at different stages is predicted and compared with the measured results. [ABSTRACT FROM AUTHOR]

Polyacrylamide (PAM) is one of the most critical materials in polymer flooding technology. However, the reservoir environment with high temperature, high pressure and high salinity will degrade PAM, which will reduce its viscosity and affect the recovery rate. In addition, previous studies lacked in-depth research on the PAM degradation mechanism and viscosity stabilization strategies. Therefore, the degradation mechanism of PAM solution in polymer flooding technology (including mechanical degradation, thermal degradation, free radical degradation, and biodegradation) and corresponding anti-degradation measures was introduced in this study, which provides a general strategy for effectively maintaining the viscosity of PAM solution. The conclusion shows that in order to maintain the viscosity of PAM solution, introducing functional monomer to modify PAM is the most essential and effective strategy. The combination of chemicals resistant to free radical degradation can further reduce viscosity loss and enhance oil recovery. The results of this study provide a comprehensive and systematic viscosity stabilization strategy that is important for PAM to reduce viscosity losses and enhance oil recovery in polymer flooding applications. In addition, modified PAM with low cost and resistance to free radical degradation should be developed in the future to meet the trend of future oil and gas resource development. [ABSTRACT FROM AUTHOR]

Compared with conventional polymer gels, nanocomposite gels have significant advantages in strength and temperature resistance. They can adapt to more severe reservoir environments and achieve the purpose of controlling water and increasing oil or temporarily plugging and diverting. Based on nanoparticles used in nanocomposite gels, nanocomposite gels can be divided into silica-based nanocomposite gels, nano-montmorillonite-based nanocomposite gels, layered silicate nanocomposite gels, laponite-based nanocomposite gels, CFA (coal fly ash)-based nanocomposite gels, and other nanocomposite gels. The researcher summarized the materials used in various nanocomposite gels (nanomaterials, main polymers, and crosslinking agents), mechanisms, excellent performance, and analyzed the shortcomings of various nanocomposite gels and current development trends. The results show that the research of nanocomposite gels needs to deal with the high temperature and high salinity oil and gas reservoir environment, and it is necessary to adopt environmentally friendly, easy-to-prepare and cheap materials. At the same time, more numerical simulation studies are needed for theoretical guidance. [ABSTRACT FROM AUTHOR]

From the perspective of clay stability mechanism, inorganic salt clay stabilizers, surfactant clay stabilizers and polymer clay stabilizers were studied, aiming to optimize the clay stabilizer for acidizing. Firstly, PDMDAAC and CPAM were successfully prepared and characterized. Then, the performance of seven clay stabilizers, including NH4Cl, KCl, dodecyl trimethylammonium chloride (DTMA), cetyltrimethylammonium chloride (CTMA), amide Gemini quaternary ammonium salt (GSA), PDMDAAC and CPAM, were compared under different conditions. The results show that the 2% salt clay stabilizer can reach 90% of the anti-swelling rate. While 1% surfactant and polymer can reach 70% and 80% of the anti-swelling rate respectively. In addition, the salt clay stabilizer has great high-temperature resistance and the polymer clay stabilizer has good scour resistance. In contrast, the surfactant clay stabilizer has poor effect in acid environment owing to critical micelle concentration. The mechanism research shows that the electrostatic interaction of the cations ionized by inorganic salt and the negative ions in the clay stabilizes clay. Besides ionizing cations, surfactant clay stabilizer and polymer clay stabilizer prevent the external fluid from entering clay interlayer through the aggregation of hydrophobic groups and the formation of polymer film respectively. [ABSTRACT FROM AUTHOR]