Abstract: Plugging of oil and gas wellbores, pipelines and equipment caused by natural gas hydrates is a major problem in the oil and gas industry and the resulting production reductions or interruptions cut into profits and bring about high costs for plug removal. In view of the lack of an accurate and reliable computational model and experimental data of plug removal by an autogenous pyrolysis plugging agent, a new mathematical model of the hydrates removal process by autogenous pyrolysis plugging agent has been established based on hydrate phase equilibrium thermodynamics and decomposition kinetics, including energy model and mass model of the hydrates removal process. The model is solved by numerical simulation. On this basis, the paper investigates the plug removal process and parameter variation laws in the pure autogenous heat system, autogenous heat system with electrolytes (salt)and autogenous heat system, respectively; based on the experimental results, the relationship among the plug removal agent dosage and concentration and removal time in the unplugging process of two agents with different concentrations and heat generation peaks have been calculated and analyzed. The results are shown as follows. (1)The calculated values of the mathematical model are in good agreement with the experimental values, indicating that the model can better calculate and analyze the blockage of hydrates and unplugging process by plug removal agent under different working conditions. (2)With the increasing of the heating temperature of autogenous pyrolysis plugging agent, the concentration of both the sodium and magnesium ions and the methanol and diethylene glycol in the agent, the decomposition rate of hydrates increases and the unplugging time decreases; when the heating temperature is less than 295 K, the system containing magnesium ions and diethylene glycol ions has a significant effect on the decomposition of hydrates. (3)The model-based plug removal agent filling amount and unplugging time demonstrates that the effect of plug removal agent is closely related to the peak heat generation, composition and concentration of the agent, and the unplugging effect of the agent used in the experiment can meet the demands on the engineering site. Under the same conditions, the effect of the ammonium salt and nitrite autogenous heat system is better than that of the polyhydroxy aldehyde autogenous heat system. The results show that the autogenous pyrolysis plugging agent of high temperature heating system can be developed during hydrates removal, and the unplugging effect can be enhanced by adding appropriate concentrations of electrolytes and alcohols without changing the heating properties of the original unplugging agent, which can achieve rapid removal of hydrates and prevent the secondary generation of hydrate.