Experimental Study On Synergistic Inhibition Of Hydrate Formation By KHI/MEG In Oil,Gas,Water And Sand Multiphase System

Adding hydrate kinetic inhibitor(KHI)is one of the main methods of "risk control" ice blockage in oil and gas gathering and transportation system.Compared with the traditional method of injecting hydrate thermodynamic inhibitor ethylene glycol(MEG),it has the remarkable characteristics of low dosage and strong applicability for deep-sea application.However,KHI will fail under some extreme working conditions.Therefore,the prevention and control of ice blockage caused by hydrate formation only through a single type of inhibitor has the problems of low economy and difficult to ensure safety in the deep-sea field.Therefore,this study takes the KHI / MEG combination as the control mode,experimentally explores its inhibition performance in oil-based and water-based systems,and provides a theoretical research basis for solving the flow guarantee problems caused by the primary formation of hydrate in the process of onshore oil and gas transportation and the regeneration of hydrate in the process of deep-sea "combustible ice" development.Therefore,this study takes the KHI / MEG combination as the control mode,experimentally explores its inhibition performance in oil-based and water-based systems,and provides a theoretical research basis for solving the flow assurance problems caused by the formation of hydrate in the process of onshore oil and gas transportation and the regeneration of hydrate in the process of deep-sea "combustible ice" development.Firstly,this study carried out the inhibition of natural gas hydrate formation by adding PVP,PVCap and PV-1 to oil-water system.The results show that the inhibition performance of PVCap and PV-1 is better than PVP,and the inhibition performance of PVCap and PV-1 increases with the increase of additive concentration;The maximum allowable undercooling of PVCap is higher than that of PVP,which can reach 20℃.After the undercooling exceeds 21℃,its inhibition performance begins to decline sharply.Subsequently,this study carried out the secondary formation and decomposition experiment of methane hydrate with PV-1 in fine mortar liquid system,and explored the performance of PV-1 in the field of deep-sea combustible ice mining and deep-water flow assurance.The results show that PV-1 can effectively prolong the induction time of hydrate in the primary formation process;However,the existence of PV-1 will lead to the rapid growth of hydrate and the decline of its inhibition performance due to the influence of memory effect in the process of secondary formation;The existence of PV-1 can enhance the stability and decomposition difficulty of hydrate.Finally,this study tested the synergistic inhibition of KHI / MEG.The results showed that the three KHI had synergistic inhibition effect with ethylene glycol(MEG),among which PV-1 had the most obvious effect.Under high undercooling(22℃),the hydrate induction period of oil-water slurry system could be extended to more than 70H;The synergistic inhibition effect of PV-1 and MEG in fine sand slurry system is obvious,and the maximum induction time can be prolonged by more than 90 hours.At the same time,this study points out that when KHI / MEG is used in combination,the two inhibitors may interact with each other in addition to their own inhibition,which plays a role in enhancing the inhibition performance of kinetic inhibitors on hydrate nucleation.