Rheological evaluation of kinetic hydrate inhibitors in NaCl/n-heptane solutions



The performance of polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap) as kinetic hydrate inhibitors (KHIs) in the presence of NaCl and n-heptane was evaluated by using a high-pressure cell in conjunction with a rotational rheometer. The addition of KHIs was found to prolong the induction time and decrease the hydrate growth. On the other hand, hydrates agglomerated more readily. PVP performed more efficiently than PVCap in delaying nucleation time but PVCap controlled the growth and delayed agglomeration more effectively. Addition of n-heptane to the system increased induction time and reduced growth. Unexpectedly, addition of KHIs in the presence of n-heptane decreased nucleation time but controlled growth effectively. Meanwhile, hydrate particles remained dispersed more efficiently and no agglomeration was detected. These observations confirm that high-pressure rheology is an additional laboratory assessment tool to evaluate KHIs under ocean field conditions. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2654–2659, 2014