Experimental Analysis of Naphthalene Solubility in Different Petroleum Fractions Under Reservoir Conditions

Abstract

This study presents an experimental analysis of naphthalene solubility in different petroleum fractions under simulated reservoir conditions. The increasing occurrence of organic solid deposition in petroleum production systems has raised significant concerns in flow assurance, particularly in deepwater and high-pressure high-temperature (HPHT) reservoirs. While extensive research has been conducted on wax and asphaltene precipitation, little attention has been paid to the solubility behaviour of aromatic hydrocarbons such as naphthalene in complex petroleum systems. The study employed a laboratory-based experimental approach using a high-pressure equilibrium cell to simulate reservoir conditions. Naphthalene was introduced into selected petroleum fractions, including paraffinic, kerosene, diesel, aromatic, and heavy gas oil fractions. Experiments were conducted over a temperature range of 30°C to 90°C under controlled pressure. The concentration of dissolved naphthalene was determined using gas chromatography and UV-visible spectrophotometry. The results revealed that naphthalene solubility increases with temperature across all petroleum fractions, with aromatic fractions exhibiting the highest solubility and paraffinic fractions showing the lowest. Pressure showed a moderate influence on solubility compared to temperature and composition. The findings confirm that the composition of petroleum fractions significantly influences naphthalene phase behaviour due to molecular compatibility effects, particularly π–π interactions in aromatic systems. The study concludes that naphthalene precipitation risk is highest in paraffinic-rich systems at low temperatures, whereas aromatic-rich systems enhance solubility and stability. These results provide valuable insights for predicting aromatic deposition, improving flow-assurance strategies, and optimising reservoir and production operations.