دانلود رایگان مقاله انگلیسی مدلی جدید برای تراوایی آسیب به دلیل ته نشینی آسفالتین - الزویر 2019

ABSTRACT

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.

5. Conclusions

In this study, a new approach is examined for asphaltene deposition in the near wellbore region. The existing permeability impairment model (solely porosity-dependent models) was improved through incorporating interconnectivity loss due to pore blockage. The governing permeability impairment mechanism (either surface deposition or pore blockage) depends upon the ratio of asphaltene particle size to the pore throat size distribution:

1. Permeability reduction in the limestone samples studied here was due to surface deposition and the effect of pore blockage is negligible. This is because of the large ratio of pore throat to the particle size.

2. For the sandstone samples, both surface deposition and pore throat plugging mechanisms almost contribute equally to the permeability reduction.

3. For carbonate samples, the pore blockage is dominant. Thus, the sample experiences a rapid sharp permeability reduction.