Condensate banking refers to the formation of condensate around the well when the reservoir pressure drops below the dew point value during depletion. As a consequence, the gas relative permeability reduces, and the formation of two phases occurs in the reservoir. Various analysis have indicated three regions with variations in fluid saturation in the radial direction from the zone immediately around to the wellbore to the furthest area. Also, well productivity and heavy components fraction of the produced fluid are compromised.
This paper aims at evidencing the formation of the condensate bank, identify the flow conditions in the reservoir and verify the most appropriate analytical model for the evaluation of this type of reservoir. An analytical and a numerical model were built using collected experimental and field data. Pressure buildup tests were analytically evaluated in terms of single-phase pseudopressure and two-phase pseudopressure. The effects of relative permeability and fluid properties along the distance were also included in the developed models. The dynamic behavior of the reservoir was assessed through a numerical compositional model elaborated to describe and regenerate pressure transient behavior along the period between well tests.
The results allowed modeling the flow zones around the wellbore and estimating the gas permeability, as well as, the skin in the areas with single and two-phase flows. Through the numerical model, it was possible to attest the existence of the three regions and to elaborate a condensate saturation distribution profile as a function of radial distance. Resultant saturation distributions ratify the lower gas quality of heavy components and allow the prediction of the evolution of the condensate bank during the time. Further, the integrated assessment allowed us to validate the results, to forecast the reservoir production and to quantify the effect of the condensate banking in the production.
The contribution of this work relies on the proposed methodology, which integrates a numerical and analytical model based on gas-condensate flow phases, rock properties, pressure reservoir transient and production behavior. Results can also contribute to a better reservoir management and prevention of the possible productivity losses of the well.