Field Testing The Turbo-Lift (Tm) Production System
Authors: Petrie Hal , Erickson John W. 
Published: December 2007

The Turbo-Lift(TM) Production System introduces a new concept in high volume downhole pumps. Employing very high specific speed blading design in a compact turbopump configuration, the Turbo-Lift(TM) system can produce 2000 to 6000 B/D in deep wells. Because the multistage axial flow turbine and pump stages have a power density on the order of five horsepower per cubic inch, deep wells can be pumped with only 20 to 40 compact stages. This can be accomplished in a "free" pump that can be circulated in and out of the well without pulling tubing. The variable speed characteristics of the Turbo-Lift(TM) System permit flexibility in operation and superior gas handling characteristics. Field tests of prototype Turbo-Lift(TM) pumps have demonstrated high volume capability and extremely low wear rates.

Introduction

The basic problem encountered in high volume artificial lift is how to impart high levels of potential energy, in the form of fluid pressure, potential energy, in the form of fluid pressure, to relatively large volume flow rates of well production fluid. A source of energy at the production fluid. A source of energy at the surface must be converted to a form suitable for transmission downhole and for transformation to fluid pressure. While the surface unit has a relatively unrestricted design envelope imposed on it, the transmission means and the downhole transformer are severely constrained by considerations of initial cost and the physical size of the wellbore. These limitations lead to high losses associated with the high power transmission rates needed for large volume lift. A premium is therefore placed on efficiency of the transmission means and downhole transformer.

The use of high pressure hydraulic fluid as a means of power transmission downhole can result in surprisingly high efficiencies. For example, to run a downhole hydraulic motor of 180 shp output at 80% efficiency requires 3309 B/D power fluid at 4000 psi. To flow 3309 B/D water in 2 1/2 tubing for 10000 ft incurs a 320 psi friction loss. This is 8% of the supplied power. Comparable downhole electric motors rated at 180 shp require 48 amperes at 2300 volts. With a bottomhole temperate of 200 degrees F, the loss in 10000 ft of #4 and #2 cable are 320 volts and 209 volts respectively. These losses are 13.9% and 9.1% of the voltage supplied. Therefore, if a reliable, high efficiency, high horsepower hydraulic downhole transformer were available, a hydraulic high volume lift system would be very attractive. To satisfy this need the Turbo-Lift(TM) System was created.

THE TURBO-LIFT(TM) CONCEPT AND HIGH VOLUME LIFT

The key element in the patented Turbo-Lift(TM) System is the downhole transformer. As shown schematically in Fig. 1, power fluid is routed through a hydraulic turbine which transforms the potential energy in the power fluid to shaft potential energy in the power fluid to shaft power. Mounted on a common shaft are the hydraulic power. Mounted on a common shaft are the hydraulic pump stages that impart pressure to the produced pump stages that impart pressure to the produced fluid. Note that the flow path chosen is inherently thrust balanced, as the pump thrust opposes the turbine thrust. Such a mechanical configuration offers the advantages in reliability and high flow rates that rotating equipment enjoys over reciprocating devices, and the potentially achievable efficiencies are far superior to jet pumps, the other common form of hydraulic downhole pumps, the other common form of hydraulic downhole pump. pump. The use of turbine drive rather than electric motor drive gives additional design and performance options with several significant advantages.