(457d) Prediction of Asphaltene Deposition in Well Bores

In the energy industry, asphaltenes are considered as potential damage creators. As the physical or chemical conditions inside the reservoir or the well bore change, asphaltenes that are originally stable in the oil phase, tend to precipitate, aggregate and / or deposit on the containing structures. This results in clogged pipes, well bores and other production equipments such as pumps. Due to this notorious behavior, asphaltenes are often termed as ?the cholesterol of petroleum?. The potential damage produced by asphaltene deposition during oil production has motivated the development of several experimental techniques and theoretical models, trying to understand and predict the asphaltene behavior under various conditions. Successful application of the Perturbed Chain version of the Statistical Associating Fluid Theory Equation of State (PC-SAFT EOS) in modeling the asphaltene phase behavior under both ambient and reservoir conditions have already been reported. The effect of factors such as pressure, temperature, composition and asphaltene poly dispersity and the effect of field conditions such as injection of CO2, oil based mud contamination and commingling of oils on the phase behavior of asphaltenes, have been described in the literature. Although important progress has been made in this area, the ability to predict deposition and possible pipe or well bore blockage due to asphaltenes, is still lacking. In this work, we present the development of a simulation tool that can potentially predict the amount of asphaltene deposition in well bores. The transport equations are coupled with kinetic models to describe the precipitation, aggregation and deposition of asphaltenes. The phase behavior of asphaltenes in oil is described by using the PC-SAFT EOS. The model predictions are compared with experimentally obtained asphaltene deposition profiles inside a capillary tube. Sensitivity analyses to understand the effect of various operating transport and kinetic parameters on the deposition profile is also presented. The effect of temperature variation inside the well bore, as the oil flows up, is also studied. Certain key aspects that could possibly improve the model predictions are also discussed. The development of a deposition simulator such as described above will certainly aid in a better understanding and prediction of asphaltene precipitation and deposition in well bores in presence of varying operating conditions. Identifying the conditions that can potentially create asphaltene problems will help operators not only to have better production planning, so as to avoid costly mistakes, but can also aid in improved new well bore designs.