A wellbore model for field-scale modeling of asphaltene plugging

Asphaltene precipitation can have profound effects on oil production during miscible flooding, heavy oil recovery, or even primary depletion. Even though asphaltene precipitation has been known to have strong effects on permeability reduction, quantitative analysis of the process has been started only recently. This paper extends the previous work to consolidate some of the hypotheses and develops a comprehensive wellbore model. The wellbore model couples the asphaltene adsorption model with a series of phenomenological models that are independently validated with either experimental or field data. These models are incorporated into the mathematical model for a linear as well as a radial system. The radial model is particularly useful for simulating asphaltene transport and deposition near the wellbore because of the continuously changing speed for this case. Initially, the governing equations were solved analytically in order to observe the role of some of the parameters independently. Following this, a series of numerical runs was conducted to observe the role of various governing parameters on wellbore parameters under more realistic representation. Experimentally, the deposition was found to be a function of permeability, flow rate, and concentration. Two distinct mechanisms were identified, namely, deposition and adsorption. Deposition could be explained in terms of trapping and mechanical plugging. The model builds on the two mechanisms described above. The coupled mathematical model predicts permeability damage due to mechanical trapping and adsorption accurately, as evidenced when compared with experimental results. Three different plugging regimes were identified and were verified with the numerical model. A series of predictive runs further clarified the transition between different flow regimes. This paper offers readers with the first wellbore model that uses irreversible thermodynamics to model adsorption and desorption and couples it with a comprehensive mechanical trapping model. The simulator applies to all reservoirs with asphaltene problems.