Influence of Asphaltene Inhibitors on Wax and Asphaltene Deposition - Are Problems Associated?

Abstract

Organic deposition formed at high temperatures in oil and gas production systems is commonly linked to instability of asphaltenes. Recent studies revealed that deposits collected in offshore production wells produced in Gulf of Mexico exhibited compositional variation pointing to a more complex fouling process than solely related to the asphaltene fractions. To better understand the mechanism of deposition and external factors that could contribute to this precipitation, crude oils and their respective deposits collected from the field were characterized for comparison in terms of properties and composition. Moreover, crude oils were treated with Asphaltene Inhibitors (AI) and Paraffin Inhibitor (PI) and tested applying three techniques: Asphaltene Dynamic Deposition Loop (ADDL), cold finger and rheology. The deposits collected from the ADDL and from cold finger were analyzed and compared to the field deposits. A lab-to-field correlation was observed when analyzing the deposits collected from the ADDL and cold finger tests. In both deposits, asphaltenes and wax fractions were observed to co-precipitate and form "Waxphaltenes". The efficiency of the AI on dispersing the asphaltenes was observed to have a major impact on the precipitation as possibly increasing the deposition of microcrystalline waxes. The influence of the AI at certain dosage rate in the precipitation of waxes is highlighted. In this research, the mechanism of asphaltene dispersion and instability of waxes in the presence of AI at low concentrations is proposed.