Effects of Poly(styrene/Pentafluorostyrene-block-vinylpyrrolidone) Amphiphilic Kinetic Hydrate Inhibitors on the Dynamic Viscosity of Methane Hydrate Systems at High-Pressure Driving Forces

Inhibiting viscosity increases from hydrate formationhas beena persistent flow assurance challenge for decades. In this study,two low-dosage kinetic hydrate inhibitors with 10 wt % hydrophobiccontent, amphiphilic block copolymers poly(styrene-b-vinylpyrrolidone) and poly(pentafluorostyrene-b-vinylpyrrolidone), were synthesized using reversible addition-fragmentationchain-transfer polymerization with a switchable chain-transfer agent.Aqueous solutions of these copolymers at 700 and 7000 ppm were loadedin a high-pressure rheometer and tested at pressures up to 15 MPagand temperatures from 0 to 6 & DEG;C. The dynamic viscosity profilesof the methane hydrates slurries were recorded, and the 700 ppm systemreached 200 mPa & BULL;s 2.2-2.4 times slower than pure water.This value was 1.3 for the poly(vinylpyrrolidone) homopolymer, suggestinga reduced tendency for hydrate particle adhesion in block copolymersolutions. At 7000 ppm, the relative time did not change substantially,achieving 2.6-2.7 times slower. However, a block copolymerwith 5 wt % poly(pentafluorostyrene) at 7000 ppm reached 3.5 timesslower, which indicates that the optimal hydrophobic content mightdiffer for each amphiphilic polymer solution. No significant effectsof molecular weight and dispersity on hydrate growth were observedfor copolymers with similar composition.