رضا آذین

Condensate formation occurs in gas-condensate reservoirs when the well bottom-hole pressure decreases below dew point pressure. Accumulation of liquid condensates may lead to vertical liquid flow. In this paper, the vertical flow effect due to gravity drainage in a gas-condensate reservoir has been investigated. To achieve this goal, a single-layer reservoir is considered and the flows with and without vertical direction are simulated with three types of fluids from poor to rich. The Governing equation of the so called Modified Black-Oil model (MBO) is solve in a radial sector using the open-source Matlab Reservoir Simulation Toolbox (MRST). When the vertical flow is considered, the results show that gravity may lead to pouring and accumulating of condensates to lower regions and wellbore is partially blocked by liquid condensates especially for the rich fluid. As a consequence, the production rates decrease. In addition, the gravity may cause a non-linear effect in the flow behavior and increase in the production rates. All results are also obtained for three values of critical condensate saturations to show effect of this parameter on the production. It has been sown that neglecting the vertical flow may cause significant error on the result of production in gas-condensate reservoirs when the fluid is rich and the critical condensate saturation is high. In these cases, gridding in vertical direction is also an important parameter in simulation of gas-condensate reservoirs.