Hydrate prevention is essential in oil and gas transportation. Low dose hydrate inhibitors (LDHIs) are more cost effective and environmental acceptive materials than traditional thermodynamic inhibitors. Evaluation of LDHI efficiency is one of the key steps in developing and studying LDHIs. Reproducibility and practicality are very important for hydrate inhibitor evaluation system.
THF hydrate ball-stop rig has been widely applied to screen chemicals as LDHIs, using ball stop times as measuring parameter. In our experiments, it was found that data produced by the rig screening showed poor repeatability. Modifications were introduced to improve the reproducibility and reliability of the rig screening results. Removal of air bubbles in the testing tubes and using sodium chloride solution to replace synthetic sea water in THF hydrate system were proved to be effective in decreasing the scattering of the results.
Moreover, a rheology system was designed to monitor hydrate formation process via correlation of shearing stress and temperature change with time. A hydrate initiating device was introduced to enhance the reproducibility of inhibition behaviour for the rheology system.
In conclusion, the combination of modified ball stop rig screening system and developed rheology system exhibited good reproducibility and practicality in the evaluation of some novel polymers as LDHIs.