Promising kinetic gas hydrate inhibitors for developing sour gas reservoirs

Abstract

The constant depletion of sweet gas reserves has led the gas industry to exploit sour gas fields, which constitute approximately 40% of natural gas resources. Under the same condition, sour gas tends to form gas hydrate more than sweet gas, resulting in severe plugging risk in the gas transportation pipelines. Using kinetic hydrate inhibitors (KHIs) is a practical method to mitigate gas hydrate formation in H2S-free environments. However, in systems with high H2S concentrations, most KHIs show poor inhibition performance. In this study, three effective KHIs were developed to inhibit gas hydrate formation in sour and sweet media. The results of constant cooling experiments indicated that KHI2 with piperazine groups acted as an excellent inhibitor in sour solution, providing the highest subcooling temperature of 13.4 °C at 1 wt %. Additionally, a lower plugging risk was observed in the presence of KHI2 as the agglomeration of hydrate particles did not occur in the system, and the motor torque value was constant during the experiment. KHI2 with butyl and piperazine groups was the best inhibitor in the H2S-free system, even better than poly(N-vinyl caprolactam). Moreover, gas hydrate simulation showed that KHI2 disrupted sour gas hydrate growth by affecting the local arrangement of water molecules to form less ordered hydrate networks. Furthermore, KHI2 decreased the hydrate structure's stability by increasing the potential energy of the system. These results present a facile method to design effective KHIs in a system containing H2S, which can be used for developing sour gas reservoirs.