Additives for Kinetic Hydrate Inhibitor Formulations to Avoid Polymer Fouling at High Injection Temperatures: Part 2 Experimental Studies with Denaturants, Osmolytes, Ionic Liquids, and Surfactants

Injection of kinetic hydrate inhibitor (KHI) polymers can cause fouling problems if the polymer solution has a deposition temperature below the well head temperatures. In part 1 of this three-part series, we reviewed various classes of additives that can raise the cloud (Tcl) and/or deposition temperature (Tdp) of thermoresponsive KHI polymers. Here, we report here our first experimental studies using two well-known KHI polymers, poly(N-vinyl caprolactam) (PVCap) and poly(N-isopropylmethacrylamide) (PNIPMAM), both with Tcl values of about 30-40 degrees C in deionized water at typical field dosages of 0.1-1.0 wt %. Changes in Tcl and Tdp were investigated for the addition of denaturants, osmolytes, ionic liquids, and surfactants at varying concentrations. Promising additives that raised the Tdp value significantly were tested for their effect on the hydrate inhibition performance of the KHI polymer. In addition, we investigated if the Tcl and Tdp of various KHI polymer solutions were affected when placed under 80 bar pressure of a natural gas mixture due to the higher solubility of the gases in the aqueous phase.