Aracaju, Brazil
Aracaju, Brazil

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Lucas M.A.,Petrobras | Lucas M.A.,PEP PBI UNIT | Borges G.R.,PEP PBI UNIT | da Rocha I.C.C.,Nucleo de Engineering AmbientalNEAM | And 3 more authors.
Journal of Supercritical Fluids | Year: 2016

The knowledge about crude oil phase behavior at high-pressures is a challenge for scientists due to inherent complexity to this systems. Some works employ model systems attempting to predict crude oil behavior, but the results are normally poor. In this sense, the use of real crude oil fractions can be an alternative to improve the accuracy of the models used in these simulations. In this work, a light oil sample has been fractionated to generate four representative fractions. An approach to estimate the critical properties of these distilled fractions using only density and vapor pressure experimental data is presented. In sequence, phase behavior of the pseudo binary (carbon dioxide (CO2) + real crude oil fractions), multicomponent (mixture of fractions + CO2) and original crude oil + CO2 systems were determined using static synthetic method and static synthetic + NIR, with CO2 molar fraction range of 0.367-0.986, temperature range of 20–80 °C and pressure up to 300 bar. Binary interaction parameters (BIP) were estimated for each pair (CO2 + distilled fraction) and employed to describe the phase behavior of a CO2 + crude oil systems with Peng-Robinson equation of state (PR-EOS) and quadratic mixing rule. The results suggest that the use of real fractions can be a safer strategy for predicting the phase behavior of petroleum in carbon dioxide. Besides, NIR spectroscopy showed to be a good alternative to study phase behavior of dark/opaque systems. © 2016 Elsevier B.V.


Borges G.R.,PEP PBI UNIT | Lucas M.A.,PEP PBI UNIT | Lucas M.A.,Petrobras | Nunes R.B.M.,PEP PBI UNIT | And 4 more authors.
Journal of Supercritical Fluids | Year: 2015

This work presents a new technique for phase behavior monitoring at high-pressure conditions. The consolidated synthetic method was modified by insertion of a near infrared probe inside the high-pressure variable-volume view cell. A system composed by carbon dioxide and a distilled petroleum fraction was used to validate the proposed methodology. The experiments were performed in the temperature range of 293-333. K, carbon dioxide mass fraction of 0.350-0.900 and pressures up to 20. MPa. The phase transitions pressures visually observed were compared with those detected by the spectrophotometer and good correlations were obtained with global mean deviation of 1.4%. Besides, it was possible to identify the type of vapor-liquid phase transitions (bubble or dew points) and the position at diagram (before or after the critical concentration) for the liquid-liquid equilibrium. The proposed methodology is promptly extended to several others systems. © 2015 Elsevier B.V.

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