Modeling Asphaltene Deposition in the Wellbore During Gas Lift Process

Abstract

Abstract Asphaltene deposition during oil production may partially or totally plug the wellbore, and results in significant reduction in well production and frequent asphaltene remediation jobs. It is well-known that injection of lighter hydrocarbons into an asphaltic oil (e.g. during gas lift) may decrease the stability of asphaltene particles in the solution and increase the risk of asphaltene precipitation and deposition. Although a great deal of research has investigated the effect of gas injection on the phase behavior and mechanism of asphaltene deposition in the wellbore, we lack a comprehensive dynamic model that can track the behavior of asphaltene during gas lift process. Therefore, a comprehensive model is required for evaluating the risk of gas lift on asphaltene deposition in production wells. This paper presents a comprehensive thermal compositional wellbore model with the capability to model asphaltene phase behavior during gas lift and determine the effect of the injected gas on asphaltene deposition in the wellbore. In the developed wellbore simulator, various numerical approaches are used to model multiphase flow in the wellbore. An equation of state was used to calculate the thermodynamic equilibrium conditions of the phases. In addition, several deposition mechanisms were incorporated to study the transportation, entrainment, and deposition of solid particles in the wellbore. Various case studies investigated the effect of gas lift on asphaltene deposition. To predict where and when the most severe damage would occur in the wellbore, we used field data of a Middle East crude oil and an injection gas. The results showed that the injection of light gas composition can negatively affect the production facilities by intensifying asphaltene precipitation in the well, which eventually results in significant reduction in the wellbore production. We believe that this comprehensive thermal compositional wellbore model can facilitate the design of work-over operation plans for asphaltic wells operating under gas lift.