Influence of wax inhibitor on fluid and deposit properties

An experimental campaign has been performed in the wax deposition test rig at Statoil's Research Center Porsgrunn: a fluid sample of a North Sea gas condensate (obtained during the well clean-up) was used for wax deposition tests with increasing concentrations of a commercial wax inhibitor. Two different production conditions (with different flow rates) were simulated. Adding 125 ppm of wax inhibitor had a strong effect on wax deposition: a reduction of 60%-90% of wax thickness (depending on the test pipe's insulation) was observed. However any further increase of inhibitor concentration had only a small additional effect. The effectiveness of the inhibitor was proven at 23 degrees C and 20 degrees C. A significant change in the deposit's characteristics was observed: with inhibitor the wax deposit became not only thinner but also significantly harder. This results from an increase in the wax content of the deposit. These findings prove the usefulness of the chosen inhibitor but they also challenge the currently used wax deposition model: adding the inhibitor did not change the input parameters used for wax prediction (WAT, wax content, solubility curve). Moreover the porosity parameter which was obviously affected by the inhibitor is currently not predicted but only used as a tuning parameter. (C) 2013 Elsevier B.V. All rights reserved.