Development of a Surface-Controlled Electric Gas-Lift Valve

Abstract

Summary In the design of conventional gas-lift installations, the size and setting of the operating valve are determined according to theoretical performance at nominal well conditions. Unfortunately, gas-lift valves are subjected to the effects of a dynamic and often transient environment that can significantly com promise operating efficiency. To manage these environmental effects better, a new electric gas-lift valve (EGLV) system in which the size of the downhole gas injection orifice can be remotely adjusted from a surface control unit has been prototyped and field tested. The EGLV system consists of an electrically operated, surface-controlled downhole valve, a downhole pressure transducer, tubing mandrel, electric cable system, and surface controller. By combining known well parameters with real-time tubing pressure and valve-position data relayed from downhole, the control unit can adjust the valve to current well conditions. This capability allows the operator to produce the well with maximum effectiveness for whatever production priorities have been chosen. Controlling valve response in this manner can be especially desirable for such applications as limited lift-gas availability, limited compressor capabilities, drawdown within designated limits, control of short-term production upsets, and areas where reservoir management objectives are specific to the application. Enhanced efficiency of gas-lift operation and optimized production were the goals of this developmental program, and testing results obtained to date have shown enough promise to initiate the next stage of the program-an advanced wireline-retrievable version of the system. Introduction The use of gas lift for primary recovery is common. Operational theory and equipment design have continued to improve over the years, but the transient nature of the gas-lift environment and numerous interrelated parameters have made the goal of optimized gas-lift performance a moving target. One of the most recently developed techniques is valve performance testing. The valve is tested for its response to a range of particular well and gas-injection conditions. Although this procedure can result in a better installation design and a better under standing of well conditions, valve orifice size and opening sensitivity are still fixed parameters; they are preset at the surface to a defined set of nominal well conditions. Wells that produce steadily and change slowly over time have the best chance of being produced efficiently on conventional gas-lift equipment. Even in those cases, however, the actual operating parameters can differ significantly from calculated nominal figures.