This study presents an experimental and numerical investigation on the effect of fluid properties on the performance curves for Gas-Lift Valves (GLV). Nitrogen and natural gas are used as the working fluids at pressure up to 66.2 and 45.5 bar respectively (960 and 660 psig). The performance of GLVs can be obtained theoretically or experimentally. However, it has been proved in the literature that the theoretical performance curves for such valves may not work appropriately for a wide range of fluids, pressure and temperature conditions.
The objective of this study is to investigate experimentally and numerically the applicability of using air instead of natural gas and how it would impact the performance of GLVs. The experimental results have been obtained using a high-pressure gas-lift testing facility located at the Louisiana State University. The GLV evaluated in the experiments is an orifice valve with 12.7 mm (32/64 in.) opening diameter. The experimental data results is compared with results obtained using a commercial simulator using a mechanistic model, and the Thornhill-Craver empirical model, which is often used to predict the gas flow through an orifice.
The results showed a significant difference between using natural gas and nitrogen as a working with respect to flow rate mainly due to the large difference in the specific gravity. Moreover, both theoretical and mechanistic models over predicted flow rates for both gases probably due to the inaccurate estimation of the specific discharge Cd of the GLV, as this value is not constant and changes with the valve and fluid types.
