Molecular Simulation Of Inhibition Mechanism Of Natural Gas Hydrate Kinetic Inhibitors

In the process of natural gas production,due to the local high-pressure and low-temperature environment,the formation of natural gas hydrate causes equipment blockage,which is mainly solved by injecting thermodynamic inhibitors and kinetic inhibitors.In this paper,through the method of kinetic simulation,the process of inhibition of natural gas hydrate growth by kinetic inhibitors is simulated,the inhibition mechanism is explored,and the optimal concentration combination is obtained by combining kinetic inhibitors with thermodynamic inhibitors.The adsorption of methane in the empty cage hydrate was calculated by the Monte Carlo method.The optimal adsorption position was exactly the same as that of methane in the methane hydrate,which verified the rationality of the structure model of methane hydrate.The maximum adsorption capacity of methane by the cage hydrate was calculated to be 64 molecules,which verified the simulation of 2×2×2 supercell configuration of I-type methane hydrate Reliability.The adsorption isotherm curve showed that the adsorption of methane in cage hydrate was sensitive to temperature change under low pressure,and not obviously affected by temperature under high pressure.The adsorption heat data showed that the adsorption of methane in cage hydrate is physical adsorption.The methane solution models of PVP and PVCap with different concentrations of kinetic inhibitors were established to simulate the growth process of natural gas hydrate in the environment of kinetic inhibitors.When the concentration of the two inhibitors was 1wt%,there is no inhibition on the growth of natural gas hydrate;when the concentration was 2wt%～6wt%,there was a specific band of PVCap with six membered ring structure The inhibition effect of PVP with five membered ring structure was better,but the inhibition mechanism was to prevent methane from entering the cage structure by adsorbing on the methane water surface,so as to slow down the growth rate of natural gas hydrate and inhibit the nucleation and growth of natural gas hydrate.In order to reduce the dosage of thermodynamic inhibitors,the effect of the mixture of kinetic inhibitors and thermodynamic inhibitors on the growth of natural gas hydrate was simulated at low temperature and high pressure.When the methanol content of the thermodynamic inhibitor is 10wt%,the mixture of 3.9wt% PVCap and 6.0wt% PVCap meets the demand of inhibiting and dissolving natural gas hydrate.The best concentration combination is 10wt% methanol+3.9wt% PVCap.