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 tho ugh asphaltene precipitation has been known to have strong effects on perme ability reduction, quantitative analysis of the process has been started on ly recently. This paper extends the previous work to consolidate some of th e hypotheses and develops a comprehensive wellbore model. The wellbore mode l 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 linea r as well as a radial system. The radial model is particularly useful for s imulating asphaltene transport and deposition near the wellbore because of the continuously changing speed for this case. Initially, the governing equ ations were solved analytically in order to observe the role of some of the parameters independently. Following this, a series of numerical runs was c onducted to observe the role of various governing parameters on wellbore pa rameters under more realistic representation. Experimentally, the depositio n 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 pluggin g. The model builds on the two mechanisms described above. The coupled math ematical 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 t he numerical model. A series of predictive runs further clarified the trans ition between different flow regimes. This paper offers readers with the fi rst wellbore model that uses irreversible thermodynamics to model adsorptio n and desorption and couples it with a comprehensive mechanical trapping mo del. The simulator applies to all reservoirs with asphaltene problems. (C) 2000 Elsevier Science B.V. All rights reserved.