Instrument subs for centrifugal well pump assemblies

An electrical submersible pump assembly, comprising:

• a centrifugal pump;
• an electrical motor operatively coupled to the pump;
• a seal section disposed between the pump and the motor for reducing a pressure differential between well fluid on an exterior of the motor and lubricant within the motor;
• at least one instrument sub releasably secured to one end of the pump above an intake of the pump;
• at least one pump stage in the at least one instrument sub, the at least one pump stage comprising an impeller and a diffuser configured for pumping well fluid;
• at least one sensor within the at least one instrument sub for monitoring parameters in the at least one instrument sub;
• at least one sensor line extending sealingly through a sensor line port in the at least one instrument sub to the at least one sensor for conveying sensed information from the at least one sensor to a remote instrument panel;
• wherein
• the diffuser of the at least one pump stage in the at least one instrument sub has flow passages for receiving well fluid;
• the at least one sensor is mounted in one of the flow passages of the diffuser;
• a diffuser port extends through a portion of the diffuser;
• and
• the at least one sensor line extends through the diffuser port to the at least one sensor.

An electrical submersible pump assembly, comprising:

• a centrifugal primary pump having a primary pump housing;
• an electrical motor operatively coupled to the primary pump;
• a seal section disposed between the primary pump and the motor for sealing lubricant within the motor;
• at least one instrument sub, comprising:
• an instrument sub housing secured by at least one threaded fastener to one end of the primary pump housing;
• a pump stage in the instrument sub housing driven by the electric motor along with the primary pump, the pump stage comprising an impeller and a diffuser;
• at least one sensor within the at least one instrument sub for monitoring parameters in the at least one instrument sub;
• a sensor line port extending through a wall of the instrument sub housing;
• a motor lead having power conductors, the motor lead being connected to an upper end of the motor and extending alongside the seal section, the at least one instrument sub and the pump;
• at least one sensor line extending sealingly through the sensor line port to the at least one sensor for conveying sensed information from the at least one sensor to a remote instrument panel;
• and
• the at least one sensor line bundling with and extending alongside the power conductors of the motor lead upward from the at least one instrument sub.

An electrical submersible pump assembly, comprising:

• a centrifugal primary pump having a primary pump housing containing a plurality of primary pump stages;
• an electrical motor operatively coupled to the primary pump;
• a seal section disposed between the primary pump and the motor for reducing a pressure differential between well fluid on an exterior of the motor and lubricant within the motor;
• at least one instrument sub, comprising:
• an instrument sub housing secured by at least one threaded fastener to one end of the primary pump housing;
• a primary pump intake located below the instrument sub housing;
• a shaft assembly rotated by the motor and extending through the seal section, the instrument sub housing, and the primary pump;
• a plurality of instrument sub pump stages in the instrument sub housing, each of the instrument sub pump stages comprising an impeller rotated by the shaft assembly and a diffuser, the instrument sub pump stages being fewer in number than the primary pump stages;
• at least one sensor within the at least one instrument sub for monitoring parameters in the at least one instrument sub;
• a sensor line port extending through a wall of the instrument sub housing;
• at least one sensor line extending sealingly through the sensor line port to the sensor for conveying sensed information from the sensor to a remote instrument panel;
• a motor lead connected to an upper end of the motor and extending alongside the seal section, the at least one instrument sub, and the primary pump;
• wherein
• the instrument sub housing has an exterior with a motor lead side portion that is in contact with the motor lead;
• the sensor line port is spaced 180 degrees from the motor lead side portion;
• and
• a portion of the exterior of the instrument sub housing spaced 180 degrees from the motor lead side portion is located radially farther from a longitudinal axis of the instrument sub housing that the motor lead side portion.