Iranian Journal of Oil and Gas Science and Technology

Abstract Asphaltene-induced formation damage is one of the complicated processes of permeability damage in porous media, particularly in the near-wellbore area. Asphaltene particles precipitate out of the bulk fluid phase during production due to pressure drop, which may reduce permeability owing to the deposition of asphaltene nanoparticles on porous media surfaces and the plugging of pore throats by larger asphaltene agglomerates. Asphaltene precipitation and deposition in production tubes and surface facilities are well-documented concerns, and many solutions for managing them are available. However, the effects of asphaltene in the reservoir, particularly in the near-wellbore zone, are little known. In this study, using an artificial porous medium, experimental data on pressure drop due to changes in parameters such as the flow rate, the type of precipitant n-alkane solvent (n-heptane alkane solvent and n-decane), and the percentage of precipitant are obtained. Next, the permeability reduction from asphaltene deposition in a porous medium is calculated. Experimental data are fitted with the proposed quasi-experimental models at different time intervals to identify the dominant mechanism in reducing clogging. One of the study’s accomplishments is determining the principal mechanism of permeability reduction (in vitro) using a reasonably basic model with the least dependent parameters and a decent approximation. According to the findings, pore throat plugging becomes the dominant mechanism of permeability reduction although filtration cake formation and surface deposition may exist during the tests.

Abstract The specific objective of this paper is to develop a fully implicit compositional simulator for modeling asphaltene deposition during natural depletion. In this study, a mathematical model for asphaltene deposition modeling is presented followed by the solution approach using the fully implicit scheme. A thermodynamic model for asphaltene precipitation and the numerical methods for performing flash calculation with a solid phase are described. The pure solid model is used to model asphaltene precipitation. The transformation of precipitated solid into flocculated solid is modeled by using a first order chemical reaction. Adsorption, pore throat plugging, and re-entrainment were considered in the deposition model. The simulator has the capability of predicting formation damage including porosity and permeability reduction in each block. A new set of independent unknowns in a fully implicit scheme is presented for asphaltene deposition modeling. In order to find the solution of these variables, the same number of equations is also presented. The description of how to solve the nonlinear system of equations is also described.