Owing to its strong adaptability and flexibility, gas lift is widely used in deliquification or production restoration for water-flooded gas well. This paper briefly introduced the advantages and adaptability of the gas-lift hard lift technology (gas lift without gas lift valve). The mathematical model based on the mass and momentum conservation was established to describe the unloading process of gas-lift hard lift and the finite difference method used to solve the model. Taking the DX180X water-flooded gas well in Kelameili Gas Field (located in Karamay City, Xinjiang, China) as example, the unloading process of gas lift hard lift was simulated. The influence factors, including the gas source of nitrogen gas or natural gas, the lifting channel of tubing lifting or annulus lifting, the kick-off pressure and operating injection pressure, were analyzed. The changes of the wellhead pressure and the bottomhole pressure during the unloading period were simulated. The results indicate that to reduce the kick-off pressure and liquid reflux, it is recommended that annulus lifting with nitrogen gas should be chosen. This study provides the technological guidance and method for the adaptable evaluation, the process design and the compressor selection for gas-lift hard lift.
Key words: Water-flooding well, gas lift, gas-lift hard lift technology, unloading process, mathematical model.
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