Abstract
Asphaltenes is normally present in the reservoir oil and for industry it is analogous to “cholesterol” since its precipitation stops the entire production and causes the loss of millions of dollars. It is an “ill defined” component of high molecular weight, which is considered most polar part in the oil compared to the other components. This polar nature of asphaltenes is imparted by heteroatoms (O, S, N, vanadium, nickel) present in its structure. Because of this polar nature, asphaltenes associate with each other and precipitate at certain temperature, pressure and composition. However, prediction of these conditions, where asphaltenes precipitates, is quite uncertain and detailed thermodynamic model together with appropriate oil characterization and experimental data is required. Asphaltenes can easily precipitates as pressure is reduced but also if the oil is diluted by light hydrocarbons eg. gas such as methane, CO2 or nitrogen. Ever since the introduction of enhanced oil recovery (EOR) method with gas this problem has become even worse.
In this presentation, we show the methodology for asphaltenes precipitation modeling using Cubic Plus Association (CPA) equation of state. We then apply it to calculate results for different reservoir oils/heavy oils and do the comparison with measured data.