Brown Lyle Wilson

Effects of Viscosity and Two Phase Liquid–Gas Fluids on the Performance of Multi-Stage Centrifugal Pumps

The paper reports on developmental research on the effects of viscosity and two phases, liquid–gas fluids on ESPs which are multi stage centrifugal pumps for deep bore holes. The test facility work was performed using pumps with ten or more stages moving fluids with viscosity from 2 to 2500 cP at various speed, intake pressure and Gas Void Fractions (GVF). For safety considerations the injected gas was restricted to nitrogen or air. The results are a series of curves representing the performance degradation of the pump. Note that in some cases the pump performances actually improved with increasing viscosity. The resulting information will allow a better understanding and more accurate prediction of performance than has been previously available. The data indicates a significant difference in performance correction when compared to the information available from the Hydraulics Institute.Copyright

Operating Electrical Submersible Pumps Below the Perforations

The ESP uses the flow of well fluid to cool the motor. This has been traditionally done by landing the ESP above the perforations, or by using a shroud to redirect the fluid around the motor. This paper examines some of the advantages and disadvantages for below perforation operation. Several options on the equipment necessary for this type of operation are presented along with a field experience of an operator in a location where below perforation operation looked to be advantageous. Introduction Where should a ESP be set in the well? The conventional recommendation for the ESP was to set the pump as high as possible in the well, where the oil would be just under the bubble point 1 . This was to save on initial cost of cable and tubing. It would also save on operating cost by reducing the voltage loss in the cable and the total friction loss in the tubing. For operation where the fluid produced was below the bubble point, it was recommended to set the pump just above the perforations. The purpose of this is to maintain as high an intake pressure as possible and there by reducing the interference of the free gas in the fluid stream. Any time that the unit was to be set below or even in the perforated zone, it was recommended that the motor shroud be used to direct the fluid flow over the motor. The oil world has changed significantly in the thirty plus years since these recommendations were published. The requirements of marginal operations to maintain profitability demand that many of the old paradigms be re-examined.