Parametric study of gas condensate flow in naturally fractured reservoirs

Naturally fractured carbonate reservoirs (NFRs) are usually characterized by complex pore systems that significantly affect the rock flow properties. Such reservoirs gained a wide interest and intensive research in the petroleum industry due to the challenges it poses in term of reservoir performance modeling. The presence of retrograde fluid in gas condensate systems, when the pressure drops below dew point, adds further complexity to the performance of NFRs. There are limited publications dealing with gas condensate flow in NFRs and the impact of variation of relative permeability with velocity and interfacial tension have so far not been studied. In this work dual porosity option of the ECLIPSE 300 compositional reservoir simulator, which includes our in-house relative permeability (k_r) correlation accounting for the positive coupling (increase in k_r by an increase in velocity and/or decrease in interfacial tension) and the negative inertial (decrease in kr by an increase in velocity) effects, has been used to conduct a series of sensitivity analysis on a single-well model. The impact of pertinent parameters; including fracture width, fracture relative permeability, fluid richness, coupling and inertia have been studied. The effect of critical condensate saturation on final recovery due to gravity drainage mechanism was also studied. The results demonstrated that positive coupling seemed to be more dominant in our study. Also, assigning unrealistic high critical condensate saturation could lead to significant underestimation of condensate recovery, especially in gravity dominated conditions. Nevertheless, the use of straight line relative permeability could lead to numerous errors in performance prediction. Copyright 2009, Society of Petroleum Engineers.