The Electric Submersible Pumps (ESP) is an efficient artificial lift method for lifting liquids from wells. The topology of the typical ESP with a pump, protector, and a motor has been fixed for many decades. The protector plays a critical role in the ESP to ensure that the electrical motor can function in the downhole environment. However, the protector's failure-prone components limit the ESP's reliability. To take the reliability of the ESP to the next level, the best approach is to eliminate the protector and thus all the associated failure modes.
The new topology of the protector-less technology for downhole rotary machinery is enabled by several magnetic technology building blocks. To eliminate the protector from an artificial lift device, the motor section is completely hermetically sealed from the downhole fluids by an isolation can. A set of magnetic couplings transmits torque from the motor to the hydraulic section via magnetic forces through the isolation can to replace the solid shaft between the motor and pump in the case of the ESP. When there is no solid shaft to transmit torque, thus no shaft seal required to prevent downhole fluids from leaking into the motor, there is no need for a protector. The thrust and radial loads from the hydraulic section are supported by magnetic bearings, which completely levitate the shafts and prevent any physical contacts between the rotating and stationary parts.
The architecture and its associated magnetic building blocks of protector-less technology are engineered into the subsurface compressor to ensure its reliability at high speed. The subsurface compressor provides both suction effects to lower intake pressure near producing zones and boosting effects to increase discharge pressure downstream of the compressor. With the lower downhole pressures and higher wellhead pressures generated by the subsurface compressor in a gas well, the gas production and recoverable reserve will increase due to higher drawdown and lower abandonment pressures. In the meantime, more liquids will be carried uphole due to higher gas velocity in the wellbore, lower intake pressure, and higher discharge temperature. The gas production in the proof-of-concept field trials of a subsurface compressor increased by 12 to 58%.
The implementations of the protector-less technology and its associated magnetic technology building blocks into the subsurface compressor are discussed in detail. The successful implementation of the protector-less technology into subsurface compressor demonstrates the ease of applying protector-less technology to the ESP. With the advantages of reliability and the ease of implementation to ESPs, protector-less technology provides a solution to ESPs when their applications require high reliability.