Improved gas lift valve performance using a modified design for GLV seat

Each gas lift valve (GLV) is a variable orifice until a fully open port area is attained (under maximum stem travel). As the ball (stem) moves away from the ball/seat contact area, the area open to flow increases until the flow area upstream to the port area equals or exceeds the fully open port area. Laboratory gas dynamic throughput testing indicates that each injection-operated GLV often does not open fully in actual operation, mainly because of the bellows stacking phenomena. As a result, the stem forms a restriction upstream to the flow path. Therefore, actual flow through the GLV can be less than expected. This paper addresses such issues and recommends a simple but effective solution. A modified design for the GLV seat was created to help reduce the required stem travel to generate a flow area equal to the port area. Theoretical calculations confirm the actual gas dynamic measurements and show that the minimum stem travel for the modified design improves from 5 to 58% compared to using a conventional sharp-edged seat. This improvement should have a significant impact on GLV performance. The modified seats for all different ports sizes were manufactured and tested using a benchmark valve test. The experiments showed that for the same stem travel, the new design has a larger flowing area than that of the sharp-edged seat. This paper details the new design, theoretical calculations, and experimental results.