Abstract

Due to the economic concerns for asphaltene related problems, chemical treatment of the near-wellbore asphaltene deposition became popular in the oil and gas industry in the past few years. However, due to the complexity and the lack of knowledge on the asphaltene problems, these asphaltene remediation programs are not always successful. Although, the field applications of these procedures have been discussed in the literature, a dynamic model that can handle asphaltene chemical remediation in the reservoir is missing.

In this paper, a comprehensive non-isothermal compositional reservoir simulator with the capability of modeling near-wellbore asphaltene remediation is developed to address the effect of asphaltene deposition on the reservoir performance. This simulator has many additional features compared to the available asphaltene reservoir simulators. The simulator can handle asphaltene behavior during primary, secondary, and EOR stages. We model asphaltene precipitation and flocculation using a solid model and a reversible chemical reaction, respectively. In addition, adsorption, entrainment, and pore-throat plugging are considered as the main mechanisms of the asphaltene deposition. Furthermore, we consider wettability alteration and porosity, absolute permeability, and oil viscosity reductions due to asphaltene. Moreover, based on the mechanisms of the asphaltene-dispersant interactions, a dynamic modeling approach for the near-wellbore asphaltene chemical treatments is proposed and implemented in the simulator. We assume that dispersants dissolve flocculated and deposited asphaltenes and transform them to colloidal asphaltenes. Dissolution of asphaltene particles using dispersants is modeled using a two-step process (1) the dispersants are adsorbed on the surface of the asphaltene particles and (2) the interactions between adsorbed dispersant and asphaltene becomes dominant. The first reaction is very fast and the second reaction is the rate-determining step.

Finally, we present case studies to investigate the effectiveness of chemical treatment jobs on asphaltene dissolution. The results show that the type of dispersant, amount of dispersant, soaking time, number of treatment jobs, and time period between two treatment jobs affect the efficiency of an asphaltene chemical treatment plan. Therefore, the success of the treatment job requires dynamic modeling. Since the presented asphaltene remediation model is very comprehensive, we can optimize the treatment plan in a field and maximize the revenue by simulation of various scenarios.

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