Analyzing the Role of Wax Crystal Morphology in Wax Inhibition Using Polymeric Additive

Abstract

Chemical additives are an effective and economical means of preventing wax deposition and gelation issues that arise during the transportation of waxy crude oil through pipelines. The wax crystal morphology is a crucial factor controlling the flow behavior of waxy oils. Therefore, analyzing the relation between wax crystal morphology and additive performance is much needed. Moreover, it is important to understand if the type of wax crystal morphology can be used as a criterion for selecting chemical additives that act as wax inhibitors. Herein, model oils with only macrocrystalline wax (Ma oil) or only microcrystalline wax (Mi oil) and different combinations of macrocrystalline and microcrystalline waxes were utilized to evaluate the wax inhibition efficacy of a commercial additive A. Rheometry, differential scanning calorimetry, and optical microscopy have been utilized to get a comprehensive picture of the additive's action (efficacy). The rheological experiments indicate that microcrystalline wax interacted better with the additive A (PAMA-based) than with macrocrystalline wax. Differential scanning calorimetry (DSC) measurements demonstrate that additive A does not significantly affect the Wax Appearance Temperature (WAT) of the model oils. Optical micrographs evince that the additive is acting by altering the wax crystal morphology in the model oils. To compare the wax inhibition efficacy of additive A, the performances of other additives B and C were also tested through rheometry and DSC. Thus, the present study provides an insight that relates the additive's action to wax crystals' morphology. We believe that this understanding will ease the struggles associated with the selection of additives as wax inhibitors for waxy oils.