(2023028) A Constant Pressure Design Approach for Improving Gas Lift System Injection Depth

The main constraint in a gas lift system is a limitation on injection volume and surface injection pressure due to the packaging and compressor capabilities available. In an ideal world, the system would have unlimited injection gas volume and unlimited injection pressure. This is often not the case with compressor availability and/or already-existing facilities. These constrains can limit the design and efficiency of a gas lift system. This study was conducted to establish a method that would allow deeper injection without increasing compressor discharge pressure. With limited injection pressure on surface, the system is limited to the injection depth that can be achieved. The design must conserve as much surface injection pressure as possible to maximize the lifting depth. 

A drawback to typical internal pressure-operated (IPO) gas lift valves is that the valves take +/- 25 psi pressure drop/reduction between gas lift valves to transition properly. These pressure drops reduce the full potential of compressor discharge pressure that is available. This decreases injection depth and ultimately decreases production or ultimate drawdown. Although these pressure drops may limit injection depth, they allow for simple monitoring of the gas lift by observing the surface injection pressure. The surveillance of these pressure drops can easily portray any problems the system might be experiencing.

With the constant-pressure design approach and the selection of an alternate style of IPO gas lift valve, an engineer can minimize or eliminate the need to take a pressure drop and allows one to fully utilize the maximum available injection pressure. This is accomplished through valve mechanics where the pressure drop is taken over a choke, rather than the ball and seat. Since the injection pressure stays constant throughout the life of the well, one loses the ability to use the injection pressure to corelate the injection depth. This is a drawback for this style IPO gas lift valve and can make it difficult to determine if the well is injecting at the intended depth.
The goal of this paper is to identify if using a different style IPO gas lift valve as the upper unloading gas lift valves and conventional/traditional IPO gas lift valves for the operating valves would be a useful application to maximize injection depth. Each system included a live downhole pressure gauge. The results from this study showed that deeper injection and higher drawdown were achieved with these systems versus a standard IPO-style design. This study was conducted with Elevation Resources in the Permian Basin.