A new model for permeability impairment due to asphaltene deposition

The existing theoretical and empirical models to describe asphaltene deposition in porous media do not consider the complicated structure of pore network. Permeability reduction due to asphaltene deposition has been mainly attributed to pore volume shrinkage (porosity reduction). However, asphaltene particles can also block pore throats which will lead to severe permeability reduction even when a large fraction of total pore volume still remains intact. Thus, there is a need for permeability models that are explicitly function of pore/hydraulic connectivity. This paper provides a review of the existing models and examines a permeability model that explain permeability impairment due to asphaltene deposition. In this study, we propose a new permeability model based on Critical Path Analysis (CPA) which is a function of average coordination number (average number of available/connected neighbor pores). Furthermore, experimental data in the literature related to limestone, sandstone and carbonate (dolomite) samples are utilized to understand combined effects of surface deposition and interconnectivity loss due to pore blockage on permeability reduction. We observed that surface deposition is the dominant mechanism in the limestone samples studied here owing to large pore throat size compared to the particle size. In the sandstone samples, both the surface deposition and pore throat plugging mechanisms contribute fairly the same in the observed permeability reduction. For the carbonate (dolomite) samples, the pore blockage is the dominant mechanism, which results in rapid sharp decrease of the permeability. It is expected that the outcome of this work improves prediction of the asphaltene deposition in the near wellbore region.