A Novel Method for the Quantitative Evaluation of Retrograde Condensate Pollution in Condensate Gas Reservoirs

Abstract

During the development of condensate gas reservoirs, the phenomenon of retrograde condensation seriously affects the production of gas wells. The skin factor caused by retrograde condensation pollution is the key to measuring the consequent decrease in production. In this study, a multiphase flow model and a calculation model of retrograde condensate damage are first constructed through a dynamic simulation of the phase behavior characteristics in condensate gas reservoirs using the skin coefficient, and these models are then creatively coupled to quantitatively evaluate retrograde condensation pollution. The coupled model is solved using a numerical method, which is followed by an analysis of the effects of the selected formation and engineering parameters on the condensate saturation distribution and pollution skin coefficient. The model is verified using actual test data. The results of the curves show that gas–liquid two-phase permeability has an obvious effect on well production. When the phase permeability curve changes from the first to the third type, the skin coefficient increases from 3.36 to 26.6, and the condensate precipitation range also increases significantly. The distribution of the pollution skin coefficient also changes significantly as a result of variations in the formation and dew point pressures, well production, and formation permeability. The average error between the calculated skin of the model and the actual test skin is 3.87%, which meets the requirements for engineering calculations. These results have certain significance for guiding well test designs and the evaluation of condensate gas well productivity.