Well Flow Modelling in a Gas Condensate Reservoir
Research output: Research › Master's Thesis
Gas condensate reservoirs have a different flow behavior from other gas reservoirs. The gas-condensate reservoir is initially gas at the reservoir condition. However, with the beginning of production, pressure decreases below dew point once heavy hydrocarbons in gas phase start to form condensates near the wellbore and consequently may limit gas flow path in the wellbore which causes gas production decrease. Thus it is important to know well flow behavior and flow patterns for calculating pressure gradient, bottom-hole pressure, predicting production rate and analysing production data. In the other words, predicting and calculating pressure gradient in gas condensate reservoirs due to complex nature of flow will be important for cost effective design of well completions and production optimization. The field being studied in this project, located in Persian Gulf coastline, is a gas condensate reservoir. Since no flow meter is installed on the wells, the individual flow rate of each well is not available. But total flow rate of two platforms which is cumulative production of twenty wells’ flow rate is known instead. And, since it is necessary to determine each well’s production rate in order to analyse production data and predict the future of production, Pipesim simulator was used to simulate choke valve and calculate the gas and condensate flow rate of each well. Having opening percentage instead of bean size in adjustable chokes is a challenging issue in calculating production rate. Therefore, 77 data points of test separators were collected to simulate the choke and to obtain an applicable relation between the choke opening percentage and the bean size. At the end, the total calculated enriched gas flow rate was compared to the total measured enriched gas flow rate and consequently the mean percentage error of 3.4 was obtained. In the next step, the wells were simulated to determine the best pressure gradient model using Pipesim software. Therefore, with measured data of wells (PSP) being used, a proper model was chosen, then with the aid of chosen model and output data from choke calculations, the wells were simulated and the bottom hole pressure was determined. Moreover, pressure-temperature profiles as well as liquid hold up profile are more outputs of this simulation. Ultimately, a sensitivity analysis was performed for the parameters undergoing uncertainty.