Experimental investigation on application of industrial coatings for prevention of asphaltene deposition in the well-string

Asphaltene deposition in the wellbore during natural depletion and EOR processes causes severe problems and increases the cost of the incremental oil recovery. Investigation of coatings as a preventive approach for operational problems during well production seems mandatory due to economic, environmental and technical limitations involved in mechanical and chemical treatment approaches. In this work, the anti-asphaltene performance of different coatings namely epoxy resin, polyurethane, phosphate, and two fluoropolymers (PTFE and PFA) was investigated by using a flow loop experimental setup. The wettability characteristics of the coated coupons were also studied by contact angle measurements to explore the correlation between asphaltene adherence tendency and wettability of the treated surfaces. Experimental results showed that despite the hydrophilicity of carbon steel, an intense increasing trend in asphaltene deposition occurred due to intrinsically high surface energy of carbon steel. An anti-asphaltene deposition ratio (R-aa) was defined to describe the anti-stick performance of different coatings compared to the uncoated carbon steel. It was observed that hydrophobic polyurethane and epoxy resin coatings showed weak anti-asphaltene performance with low R-aa values where they have reduced asphaltene deposition 10% and 48.34%, respectively. Super-hydrophilic phosphate coating reduced the asphaltene deposition by 91.25% via formation of a water film on the coated surface. Finally, the fluoropolymer coatings showed the best performance among investigated samples by anti-asphaltene deposition ratios of 99.89% and 99.94%. The low surface energy of these coatings introduces them as non-reactive surfaces compared to other coatings, hence accepting much less asphaltene deposition.