Modeling of Asphaltene Precipitation using Associating & Non-associating EoSs
Asphaltene is the most heavy and polar fraction of reservoir oil. It precipitates out of the oil due to change in temperature, pressure or composition. The crude oil can be divided into maltene (deasphalted fraction) and asphaltene fractions. The maltene fraction can be further divided into saturates, aromatics and resins fractions. All of these fractions consist of polydispered components. Asphaltene precipitation is more susceptible during the gas injection to maintain reservoir pressure or increase the oil recovery. In addition, asphaltene containing crude is generally blended with one or more crudes to maintain the properties of feedstock (blended crude) to the refinery. In certain cases, the blending of the crudes is not compatible and the solubility of asphaltene fraction into the blend may reduce. The precipitation of asphaltene can result into fouling and coking of preheat trains, heat exchangers and pipestill furnace tubes in the refinery. Asphaltene precipitation is still an unsolved flow assurance problem for oil industries.
In this presentation, we will discuss about the modeling approach to calculate asphaltene onset conditions using the Cubic Plus Association (CPA), Perturbed Chain Statistical Association Theory (with association and without association term) and Soave-Redlich-Kwong with Huron-Vidal mixing rule equations of state. We will also show whether we can calculate the amount of precipitated asphaltene (and not just the onset conditions) while mixing different n-paraffin precipitants. Asphaltene onset conditions from mixing of different crudes (degassed oils) will also be discussed. In addition, the calculations of PVT (Pressure-Volume-Temperature) properties with the CPA modeling approach will be shown.