Hydrate formation and deposition behaviors with kinetic inhibitors under pseudo multiphase flow

Abstract

With the successful application of kinetic hydrate inhibitors (KHIs) on hydrate plug prevention, there is a growing trend towards the development of affordable and environmentally friendly KHIs for solving challenges of high cost and inadequate biodegradability from their commercial KHIs. Therefore, further evaluation on the inhibitory effect of the developing inhibitors is needed under multiphase flow conditions. In this study, a high-pressure, fully visible rocking cell were used to simulate the multiphase transportation and both commercial KHIs and environmentally friendly KHIs were considered. Under the flow conditions of 60 % liquid loading and 20 % water cut, the results demonstrated that PVCap showed excellent inhibition performance with no hydrate formation at concentrations of 0.5 wt%, 0.2 wt% and 0.1 wt%. Although pectin exhibited certain inhibitory effect on hydrate growth rate and formation quantity, but it demonstrated a strong promoting effect on hydrate nucleation opportunities and rates. However, sodium alginate, which shares similar hydrate inhibition characteristics with pectin, exerted significantly promotional effects in terms of induction time, growth rate, and water conversion. Furthermore, the addition of pectin and sodium alginate led to the formation of hydrate balls in several test runs, resulting in complete pipeline blockage. Another noteworthy discovery was the relationship between the growth rate and final water conversion of hydrates, which exhibited an initial increase followed by a decrease, while the induction time exhibits an inverse trend, as the flow velocity increased.