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2005-2007: Research Project on Asphaltene Modeling

BACKGROUND

The exact nature of asphaltenes and the mechanisms behind aspahltene precipitation are not fully understood. This makes it very difficult to develop an accurate and reliable model for asphaltenes. There are today no standardized measurements on asphaltenes that could be used to tune the model to obtain more accurate simulation results.

ASPHALTENES

Asphaltenes may precipitate from petroleum reservoir fluids as a highly viscous and sticky material that is likely to cause deposition problems in production wells and process equipment.

WORK TO DATE

The available models have been reviewed and the most likely candidate for success has been found in the PC-SAFT model (Perturbed Chain Statistical Association Fluid Theory). The PC-SAFT model also shows promising results in equilibrium calculations. This indicates that the model could be used for the whole spectrum of thermodynamic calculations.

MODEL REQUIREMENTS

A satisfactory asphaltene model must quantitatively handle gas-oil-asphaltene equilibria at reservoir and production conditions. It must be sensitive to pressure to represent the phase splits occurring at isothermal conditions as a result of a pressure reduction. This requires a very accurate description of the volumetric behavior of both the oil and the asphaltene phase at high pressures. An important aspect of asphaltene phase behavior is the possible asphaltene precipitation in connection with Enhanced Oil Recovery (EOR). The model should quantitatively assess the influence on the asphaltene onset pressure of a possible injection of natural gas or CO2.

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