Numerical modelling of the effect of Asphaltene precipitation on wells’ productivity Index in one of Iranian South West fractured reservoirs

Asphaltene precipitation could decrease the effective mobility of hydrocarbon through pore throats plugging and as a result, rock permeability. Though, sometimes changing fluid viscosity and wettability could also be a determining factor in determining wells’ productivity.This study is aimed at modelling asphaltene formation and its consequences in the reservoir and evaluating them in terms of wells’ productivity Index. In this work, after implementing a thermodynamic asphaltene model based on Cubic PR-EOS and exporting this into a compositional simulator by an in-house PVT software, the validity of base asphaltenic simulation model is evaluated and then, dynamics of the precipitated asphaltene are investigated through deposition, porosity reduction, permeability reduction, and viscosity change models. On the other hand, since there is a single-phase flow in the reservoir, the wettability alteration is not taken into account. After PI evaluation, by doing a sensitivity analysis, the most significant parameters worsening asphaltene damage are identified.The results indicate that the damage triggered by asphaltene deposition, through plugging, decreasing permeability and changing viscosity was disclosed as a decline in productivity index curves. Results show that permeability alteration is the main cause of reducing wells’ productivity indices compared with viscosity alteration. The results also show that although adsorption has a significant effect on the decline in wells’ PI, but plugging is the more determining factor.

Keywords:

Asphaltene , Thermodynamic model , Deposition model , Compositional Simulator , Productivity Index