Computational fluid dynamic(CFD)simulation of pilot operated intermittent gas lift valve

To design an efficient intermittent gas-lift installation,reliable information is needed in the performance of all process components,from the outer boundary of the reservoir to the surface separators.The gas lift valve is the one critical component that affects the design of the whole system.In intermittent producing system,the pilot gas-lift valve is extremely used to control the point of compressed gas entry into the production tubing and acts as a pressure regulator.A novel approach using computational fluid dynamics simulation was performed in this study to develop a dynamic model for the gas passage performance of a 1-in.,Nitrogen-charged,pilot gas-lift valve.Dynamic performance curves were obtained by using Methane as an injection gas with flow rates reaching up to 4.5 MMscf/day.This study investigates the effect of internal pressure,velocity and temperature distribution within the pilot valve that cannot be predicted in the experiments and mathematical models during the flow-performance studies.A general equation of the nonconstant discharge coefficient has been developed for 1-inch pilot valve to be used for further calculation in the industry without using CFD model.The developed model significantly reduces the complexity of the data required to calculate the discharge coefficient.

Computational fluid dynamic(CFD)modelling of transient flow in the intermittent gas lift

A computational fluid dynamics model(CFD)is developed for intermittent gas lift techniques.The simulation is conducted for a test section of 18 m vertical tube with 0.076 m in diameter using air as injection gas and oil as a formation fluid.The results obtained from the CFD model are validated with the experiment results from the literature.The current study shows that computational modeling is a proven simulation program for predicting intermittent gas lift characteristics and the transient flow parameters that are changing with time and position in the coordinate system.The model can predict the slug velocity behavior for different injection pressure.The slug velocity profile shows three regions;the first region is the rapid acceleration at the initial time of injection,the second region shows the nearly constant velocity until the slug reaches the surface and the third region is again the rapid acceleration when the liquid starts to produce.Also,the results obtained from this model show that as the gas injection pressure increases,the liquid slug velocity increase,and the region of the constant velocity decrease.The effect of the injection time on the liquid production rate has been studied for two different gas injection pressures of 40 psig and 50 psig.The developed model shows that more than 50%of the liquid production is coming from after flow period.