Gas Lift Systems - New Mexico Institute of （气举系统新墨西哥研究所）.pdf

Gas Lift Systems Gas is injected continuously or intermittently at selected locations, resulting in the lifting of the produced fluids to the surface. This is accomplished by lowering the hydrostatic load in the tubing by the addition of the gas. The lowering of the bottom hole pressure is also accomplished. The lifting of well fluids is accomplished by one of two methods: 1) Continuous – Continuously injecting gas into the tubing or casing at a predetermined depth to reduce the pressure opposite the producing formation. 2) Intermittent Flow – Injection of high pressure gas into the tubing at sufficient volume and pressure to lift the fluid head accumulated above the valve with maximum velocity. (De-watering gas wells) Advantages of Gas Lift 1) Low initial and operating costs 2) Flexibility of production, can produce at high and low rates 3) Effectively produce high GOR and WOR wells 4) Deep wells, deviated wells 5) Subsurface equipment can use wireline workover techniques 6) Dual completed wells Factors that limited effectiveness of gas lift 1) Sour gas 2) Wet gas subject to freezing 3) Paraffin 4) Low viscosity crudes The four well categories considered for gas lift 1) High PI – High BHP continuous 2) High PI – Low BHP intermittent 3) Low PI – High BHP continuous 4) Low PI – Low BHP intermittent Note; here High BHP is a BHP that can support the liquid for 70% of depth, low is less than 40% of depth. Low PI is less than .5 BOPD/psi. Continuous Gas Lift System Design Factors 1) Gas injection depth, pressure and GLR for desired production 2) Principles of unloading operations 3) Well gradients 4) Gas lift valve spacing principles 5) T