Inhibition of structure II hydrates formation by salt-tolerant N-vinyl lactam-based terpolymers

Abstract

This work presents experimental results on the inhibition performance of low-dosage hydrate inhibitors (LDHIs). The studied LDHIs, namely terpolymers of N-vinylcaprolactam and alkylimidazolium bromide or benzyl ammonium chloride and hydroxyethyl methacrylate or acrylamide derivatives, were synthesized at the Mexican Petroleum Institute with the objective of producing high performance inhibitors with higher cloud points than that exhibited by the poly(N-vinylcaprolactam) homopolymer. Three experimental methods were used to evaluate the hydrate inhibition performance of the synthesized terpolymers: 1) the capacity to inhibit the formation of tetrahydrofuran (THF) hydrates (atmospheric pressure and −0.5 °C); 2) the capacity to inhibit the formation of natural gas hydrates under high pressure and low temperature conditions (∼6 MPa, ∼1 °C, a subcooling of 16 °C for the studied natural gas sample); and 3) the determination of the cloud point temperature of the terpolymers in aqueous systems with varying salinity (atmospheric pressure and temperatures ranging from 2 °C to 81 °C). The inhibition performance and the high solubility (in highly saline aqueous systems) of the synthesized terpolymers indicate that these compounds could be considered promising kinetic hydrate inhibitors or gas-well anti-agglomerants to prevent or delay the formation or agglomeration of clathrate hydrates during the production and transport of hydrocarbons.