Evaluation of Wax Inhibitor Performance through Various Techniques

Abstract

Various techniques were used to compare the effectiveness of a commercially available wax inhibitor (WIA) to a newly developed wax inhibitor (WIEP) using a highly waxy Wyoming crude oilwhich causes plugging within wellbores and pipelines. The two additives were compared using centrifuge experiments, cold finger tests, and the precipitation and redissolution waxphaltene determinator (WD) method. Centrifuge tube experiments, and cold finger tests, showed that the newly developed WIEP additive was significantly more effective at reducing the amount of ambient temperature wax crystallites in the crude oil, as well as reducing the amount of wax deposited on a cold finger. WD analysis was performed on model compounds to differentiate between shorter and longer n-paraffins. Whole crude oils, ambient temperature waxes centrifuged from the oils, and waxes from cold finger deposits were also analyzed by the WD method. Taken together with high temperature gas chromatography, the WD profile of whole crude oils readily distinguishes shorter n-paraffins from the more problematic longer n-paraffins that are prone to crystallization at ambient temperature. For treated Elliott crude oil, the WD Analysis profile showed a consistent decrease in wax with WIA concentration to give a linear correlation; however, a less consistent change was observed with the WIEP additive. By applying the WD analysis to the additives themselves, it was elucidated that the WIEP additive contained components that were highly polar and/or more associated. This observation suggests that components in the WIEP additive may self-precipitate to a greater degree than becoming incorporated with the waxes during the WD separation. This effect caused the WIEP to appear as though it is not as effective as the WIA additive in the WD analysis.

A Critical Review of Controlling Paraffin Deposition in Production Lines Using Chemicals

“…100 However, very few studies have investigated the effect of chemical additives on the solubility curve. 101 Adams et al 101 reported that adding chemical additives inhibited the wax precipitation using centrifuge tests, which revealed that the Pour point is the temperature at which the crude oil starts losing its fluidity. Once the yield stress of the gel is high enough to exceed the pipeline pressure, then the pipeline cannot be operated.…”

“…Several techniques can be used to obtain it, such as DSC, filtration and centrifugation, pulsed NMR, FT-IR, and HTGC . However, very few studies have investigated the effect of chemical additives on the solubility curve . Adams et al reported that adding chemical additives inhibited the wax precipitation using centrifuge tests, which revealed that the inhibitor mechanism is not just simple “sequestering” effects.…”

“…However, very few studies have investigated the effect of chemical additives on the solubility curve . Adams et al reported that adding chemical additives inhibited the wax precipitation using centrifuge tests, which revealed that the inhibitor mechanism is not just simple “sequestering” effects. It is plausible that chemical additives can affect the thermodynamic properties of the crude oil further affecting the wax deposition process.…”

“…Moreover, there is no model available to predict the wax precipitation in the presence of chemical additives for now. Systematic studies are required to validate the Adams et al’s results, investigate the thermodynamic behavior, and model wax deposition with chemical additives.…”

Advances in and Perspectives on Strategies for Improving the Flowability of Waxy Oils

“…Perez et al 235 found that pour point depressants are often ineffective when the crude oils have high boiling points or high aromatic content or contain high content of wax molecules with nalkane carbon chains greater than 25, while they are effective when crude oils have high asphaltene content and high resin or total acid value or contain wax molecules with n-alkane carbon chains less than 25. Adams et al 236 developed an automated separation wax tester that can discriminate easily crystallizable wax fractions from crude oil, thus allowing preliminary and rapid identification of crude oil sensitivity to pour point depressants. Senra et al 27 found that C 32 was able to cocrystallize with C 36 but stearic acid did not cocrystallize with either C 32 or C 36 at any concentration.…”