Kinetic inhibition of hydrate formation in oil-water systems and its synergistic inhibition with ethylene glycol

A hydrocarbon gas drive production method is used in an oil field in Changqing. The use of this method may lead to a high gas-oil ratio (30~100 m³/t) of well flow. This study carried out relevant experimental research into hydrate prevention and control problems that are common in the process of the hydrocarbon gas drive method. Compared with the prevention and control scheme of adding a traditional thermodynamic inhibitor(THI), a kinetic inhibitor(KHI) has attracted more and more attention for its advantages of low dosage, high efficiency and environmental protection. However, according to a large number of field examples and experimental research results, it can be found that the effect of a single inhibitor is not ideal, and the inhibition effect of traditional KHI is greatly affected by temperature. Under high undercooling, its suppression may fail. Adding synergists to the kinetic inhibitor system enhances the inhibition effect. This has become an important research topic Two kinetic inhibitors of PVP(polyvinylpyrrolidone) and PVCap(polyvinylcaprolactam) and their synergistic inhibitors combined with mono-ethylene glycol (MEG) were experimentally studied in a 500 mL autoclave. In the process of hydrate formation, the inhibition effect of compound inhibitors on hydrate formation was studied. The inhibition performance of the two kinetic inhibitors was tested from the perspectives of inhibitor concentration, maximum allowable undercooling and the effect of combination with MEG. A total of 42 groups of experiments were carried out in this study. The experimental results show that the inhibition ability of kinetic inhibitor PVCap is better than that of kinetic inhibitor PVP at the same mass concentration. PVCap still showed good inhibition ability at nearly 20 ℃ undercooling. In the synergistic experiment of PVCap and PVP combined with MEG, it can be found that they all showed a certain degree of synergistic inhibition. The synergistic effect of PVCap and MEG is more obvious. The synergistic inhibitor combination of 3 wt%PVCap and 5 wt%MEG can prolong the induction period of natural gas hydrate to more than 9 h under high undercooling (22 ℃), which shows that a reasonable and effective synergistic inhibition scheme can effectively improve the inhibition performance of KHI, help to promote the application of KHI in the field of oil and gas resources under a domestic high undercooling environment, and provide technical support for efficiently solving the problem of hydrate prevention and control in oil and gas production under high undercooling conditions.