A new approach to model asphaltene induced permeability damage with emphasis on pore blocking mechanism

Abstract

Asphaltene deposition in porous media could reduce permeability up to 90%. Nonetheless, this would occur often for a slight reduction in porosity. This, in turn, indicates that while the volume of deposition is not noticeable it can block pore throats and consequently, it affects conductivity of porous media. This phenomenon is strongly dependent on the pore structure, initial porosity and permeability and also precipitated asphaltene particle size which is a function of oil composition and the condition of asphaltene precipitation. Often, regardless of these facts, permeability reduction is simulated by a power law porosity-permeability relationship. This study highlights the necessity of a new permeability model based on previous studies and experiments. A new permeability reduction model based on Gruesbeck and Collins' parallel plugging/non-plugging pathways model is proposed. The model considers two different mechanisms including surface deposition and throat plugging based on pore size distribution, and is implemented into an IMPEC (Implicit Pressure and Explicit Composition) compositional cylindrical simulator. Precipitated asphaltenes, considered as moving phase during simulation, are characterized by LLE (Liquid/Liquid equilibrium) calculations using PR-EoS. It is observed that permeability damage due to throat blocking is severe and abrupt while surface deposition is a gradual mechanism. Furthermore, convexity and concavity of permeability reduction curves are obtained for plugging and non-plugging pathways, respectively.