Visualizations of Asphaltene Inhibition Mechanisms with Two Classes of Chemistries

Abstract An effective asphaltene inhibitor (AI) changes the asphaltene particle growth behavior(s) and decreases the tendencies of deposition. An AI may reduce asphaltene particle size and reduce deposition for one crude oil yet aggravate the situation in another. Therefore, seeking AIs that shift particle growth behaviors in various ways and understanding their inhibition mechanisms are in our interest. Here, we investigated the inhibition mechanisms of two classes of AIs by asphaltene particle visualization and deposition methods. Two classes of AIs, lecithins (L) and polyolefin esters (PE), with various grades were studied. A typical lecithin is a mixture of phospholipids. The most polar fraction is phosphatidylcholine (PC). We examined three lecithins, L-1, L-2, and L-3 with 15%, 50%, and 92% PC, respectively. PE-1 and PE-2 have the same alcohol core but different dispersing group ratios. PE-2 and PE-3 have different alcohols and the same dispersing group ratio. Turbiscan test, microscope visualization of asphaltene particle growth with image analyses, and dynamic deposition test were used to evaluate asphaltene inhibition performance and corresponding mechanisms. In Turbiscan tests, L-1 disperses asphaltene the best, L-2 performed mediocre, and L-3 performed poorly. The polar PC fraction does not help dispersing. All the PEs showed good to great dispersancy. Subsequently, a newly developed benchtop microscope method with particle size, count, and shape analyses capabilities, was used to study asphaltene particle growth with a Middle East crude oil. Blank showed particle size and count growth with time. L-1 significantly inhibits particle count and size growth. Although PEs did not delay time of particle formation, the numbers decreased, and shapes became more uniform. Interestingly, PE-1 showed evidence of promoting of particle growth in the beginning phase. Results of PEs indicated different polar and dispersing group ratios can result in performance differences despite in the same chemistry class. Final deposition tests showed L-1, PE-1 and PE-2 perform well, significantly reduced deposition with different mechanisms. The structure-property relationships from two classes of AIs were studied. Both classes of AIs demonstrated reduction depositions can be achieved by unique alterations of asphaltene particle growth behaviors. Understanding different AI mechanism will aid future formulations to combat diverse asphaltene challenges.