Applications of line-pack model of gas flow in intermittent gas lift injection line

Abstract

Intermittent gas lift is one of injection techniques for mature wells with low-productivity. This technique has two periods i.e. shut-in and production periods. During shut-in period the choke is closed, and the gas flows from the compressor into the gas-line. Furthermore, production period takes place when the choke is open to allow the gas flows into the tubing-casing. This process is similar to line-pack and line-draft in transient gas flow. It is known that the upstream choke pressure should be high enough to lift the oil. Hence, it is very important to control the shut-in period. In this paper, a line-pack model for an intermittent gas lift is constructed. The model is used to predict high-pressure performance at the upstream choke. Moreover, the model is compared with field data from literature. The effect of opened-closed choke to the pressure and the gas rate is analyzed. Sensitivity analysis with respect to gas-line length, gas rate, discharge pressure, and duration of shut-in are shown. The results show that the pressure at the upstream choke can be estimated as well as the duration of shut-in which are critical in increasing the pressure. This model is important for avoiding production operation failure.