Study of the Morphology of Wax Crystals in the Presence of Ethylene-co-vinyl Acetate Copolymer

Formation of wax depositions in production tubing and pipelines is a common problem in petroleum industry. It is in cases where fluid temperature is less than the wax appearance temperature, which is the result of reduction in wall temperature of pipeline as the environment temperature decreases. In such conditions the wax compounds precipitate out of solutions and form crystals with complicated structures. The overcoming such problems are costly and time consuming. Different methods such as using inhibitors are used to manage this problem. Inhibitors can be used to prevent wax deposition. The authors studied the morphology of wax crystals and its changes with addition of ethylene vinyl acetate copolymer using scanning electron microscopy. The results show that wax depositions in the absence of polymer are plate-like crystals. As the time increases the thickness of deposit increases and the change from plate-like crystals to spherulites (that is the sidelong growth of crystals around a nucleus) or semispherulites were observed. In addition, a small amount of ethylene vinyl acetate changes the morphology of wax crystals to mal crystals (the small crystals that are not grown). In fact when ethylene/vinyl acetate is used as an inhibitor, it can coalesce with wax crystals and interfere with the growth of crystals. So the ability of crystals to interconnect and form networks decreases. Therefore more crystals with smaller size can be produced. As a final result the removing of wax crystals will be much easier.