Phase Behavior Calculation And Systems Analysis In Gas Condensate Reservoir

The complicated phase transition is coming alone with the exploration of gas-condensate reservoir while enormous impact is brought to gas well productivity by the separation of gas condensate. Based on the phase behavior of gas-condensate reservoir, this thesis studies the relationships between the liquid composition variety and pressure as well as temperature through EOS. Besides, the result of the flash computation was applied to predict dynamics of inflow and outflow conditions in condensate gas wells, so as to improve the accuracy of dynamic production prediction.The main tasks are as follows:1. According to the features and service conditions of EOS, SRK and PR, two cubic EOS of Hydrocarbon systems, was used to phase equilibrium calculation. According to the comparison of the dew-point pressure and the result of the flash computation as well as the existing measured data, EOS with high precision was selected to the production prediction of dynamics.2. In combination with the transfusion characteristics, three areas was divided:Gas phase transfusion area which pressure is higher than the dew-point pressure, Gas phase transfusion area which pressure is lower than the dew-point pressure, higher than critical flow pressure and Gas-liquid transfusion area which pressure is lower than condensate critical flow pressure. The flash computation was used to calculate the physical property parameter of compound under different pressures, so as to predict the relationships between gas well productivity and bottom hole flowing pressure.3. According to the well test data, equation were fitted to the existing production.Comparing the situation of considering and not considering of the phase change, considering the effect of anti-condensate pollution in gas condensate reservoir.4. According to the characteristics of gas condensate flow in the wellhole, the wellhole flow is divided into three different situations. Different models are selected to calculate the wellhole pressure distribution. While bottomhole pressure is greater than the dew point pressure, in the fluid flow from the bottom to the wellhead, wellbore pressure distribution is always greater than dew point pressure, a single gas pipe flow calculation model is used to calculate the pressure distribution. While bottomhole pressure is greater than the dew point pressure and wellbore pressure is lower than the dew point pressure, retrograde condensate appeared in the wellhole, the oil form accounted for a small proportion, imitated single-phase flow was picked. While wellbore pressure is lower than the dew point pressure, the oil form accounted for a large proportion, large deviation was made by imitated single-phase flow model. Gas-liquid flow model was considered.5.Combining with temperature and pressure calculation models, considering phase behavior variety, accurate temperature and pressure distribution was calculated and solve steps for particular models were given.6. According to the flash computation and stress situation of the liquid drops, appropriate model is chosen to calculate the minimized critical liquid-carrying flow so as to judge whether the effusion is existed in gas-condensate wellhole.7. Visual Basic computer programming language is used to design software of phase behavior calculation, mainly used for flash computation of the condensate gas reservoir, the distributed of wellhole pressure and temperature considering of the phase transition as well as the calculation and judgment of the minimized critical liquid-carrying flow in wellhole.