Production Operation of Submersible Pumps with Closed-Loop Adjustable Speed Control

Submersible pump performance in a given installation is determined by the intersections of the pumping load line with the pump capability curves. With fixed pump speed, the operating point on the head-capacity curve moves as the well productivity changes, and operation may be then outside the desired range. Efficiency and reliability are thereby reduced. With adjustable speed pumping, the operating point may be held within the desired range at high efficiency, while production is changed to match the well capability. Cycling or throttling may be avoided. Production is optimized if the well fluid level is held as low as possible, while avoiding pump-off, cavitation or gas-lock conditions. This may be achieved by using closed-loop control of pump speed with the feedback of either downhole pressure or motor current data or both. Practical experience has demonstrated the reliability of these techniques and the resulting ability to confidently operate with a lower fluid level, which is maintained constant through changing productivity.