Experimental phase behavior and solubility parameter for crude oil + methane [T = 311.15–373.15 K] and crude oil + methane + CO2 mixtures [T = 343.15–383.15 K]

• Published in: Fuel (Guildford) Vol. 288; p. 119675
• Main Authors: Romero Yanes, José F., da Costa, Moacir F.L., Sampaio, João P.G., Chacón Valero, Angélica M., Feitosa, Filipe X., de Sant'Ana, Hosiberto B.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15-03-2021; Elsevier BV
• Subjects: Asphaltenes; Carbon dioxide; Chemical precipitation; Compressibility; Crude oil; Energy; Gas composition; Internal energy; Internal pressure; Methane; Oil; Parameter identification; Phase behavior; Phase equilibria; PVT; Reduction; Solubility; Solubility parameter; Solubility parameters; Systems analysis; Temperature; Solubility parameter; Phase behavior; Crude oil; Carbon dioxide; PVT
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119675

Asphaltenes insolubility is recognized as an important flow assurance problem during crude oil production. In this work, phase behavior for crude oil + methane and crude oil + methane + carbon dioxide mixtures were studied for two Brazilian pre-salt crude oil samples, with low asphaltenic content. From PVT compressibility experimental data, phase equilibria were studied based on solubility parameter, cohesive energy, and internal pressure approach. For the crude oil + methane systems, methane content was evaluated from 25.0 to 75.0 mol%, at a temperature range from 313.15 to 373.15 K. No asphaltene precipitation was observed and a minimal solubility parameter was reached at the richest methane content. Additionally, a marked reduction of cohesive energy was observed increasing methane content, probably associated to the system asymmetry. For the crude oil + methane + CO2 systems, a constant gas composition of 75.0 mol% was studied. Carbon dioxide (CO2) content varied from 0.0 to 100.0 mol%, balanced with methane, for a temperature domain of 343.15 to 383.15 K. For these systems, asphaltene insolubility regions were detected. Moreover, the addition of CO2 contributed to asphaltene stabilization. Solubility parameter and internal energy increases were properly identified for these mixtures and it could be associated to the asphaltene region reduction.