Experimental study for the blockage of gas hydrates and evaluation of kinetic inhibitors

Abstract Technologies for preventing hydrate blockage play an important role in oil and gas production, transportation and processing. In this paper, a fully visual rocking cell was used to study the effects of water cut, surface wettability and kinetic inhibitors (PVCap, apple pectin and three ionic liquids) on gas hydrate nucleation, growth and blockage. The amount of water converted to hydrates reached the highest when the water cut was about 60%. The evolution process of hydrate was observed by CCD camera, including initial crystallization, water film condensation, forming the hydrate bed, and the top blockage. The hydrophilic surface can reduce the nucleation rate of hydrate to some extent, but it can not reduce the final hydrate production. The hydrophobic surface can increase the formation rate of hydrate and the amount of water converted to hydrates, but the pipe blockage did not occur because it is difficult for hydrate to adhere to the pipe wall. In terms of induction time, the inhibition to structure II hydrate of 0.2 wt% apple pectin was similar to that of PVCap, and the inhibition of high concentration apple pectin decreased because of its low solubility. Apple pectin can delay the formation rate of hydrate, but will not change the final production of hydrate. [HMIM]BF4 and [EMIM]Cl can make hydrate disperse evenly in water and prevent pipeline blockage, which play a role like anti-agglomerates. From the inhibition effects of cations and anions on hydrates, the order was as follows: Cl− > BF4−, [HMIM]+ > [EMIM]+. This study might provide a basis for hydrate plugging prevention.