Application of in-situ heat generation plugging removal agents in removing gas hydrate: A numerical study

Abstract

Under the condition of low temperature and high pressure, natural gas will form solid gas hydrates in oil and gas wellbore and pipeline, resulting in blockage, pressure increase, production reduction, and even shutdown. Methods such as heat preservation, heating, and injection of inhibitors are often used in engineering to avoid the formation of hydrates. The latter, injection of inhibitors, is the most widely used means of hydrate prevention and control at present. A special inhibitor, namely an in-situ heat generation plugging removal agent, has the advantages of both heating and chemical plugging removal and is a kind of hydrate inhibitor with great potential. In this study, a new mathematical model is developed based on hydrate phase equilibrium thermodynamics and decomposition kinetics, which is used to solve the heat and mass transfer problems in the plugging removal process of the gas hydrate by using in-situ heat generation plugging removal agents. Numerical simulation is used to solve the mathematical model, and the plugging removal process and parameter variation of pure in-situ heat generation system (high/medium/low temperature), electrolyte in-situ heat generation system (containing Na+/Mg2+), and alcohol in-situ heat generation system (containing MeOH/DEG) are studied respectively. Based on the experimental results, the quantitative relationship between the plugging removal time, the dosage, and the concentration of the plugging removal agent is calculated and analyzed. Our proposed model is verified through experimental study and the calculated values of the mathematical model are in good agreement with the experimental values under different working conditions. It is concluded that the rapid removal of hydrates and the prevention of secondary formation of hydrates can be achieved by configuring the high-temperature in-situ heat generation plugging removal agents, and the efficiency of plugging removal can be enhanced by adding appropriate concentration of electrolyte and alcohol without changing the heating property of the original plugging removal agent. This study can provide theoretical guidance for the safety of oil and gas flow and the efficient development of hydrate.