This invention relates in general to electrical submersible well pump assemblies and in particular  to  instrument  subs that  mount  to  a  centrifugal pump.

BACKGROUND

Electrical submersible pump assemblies are commonly used in hydrocarbon producing wells to pump well fluid. These assemblies include a rotary pump driven by an electrical motor. A seal section coupled between the pump and motor reduces a pressure differential between well fluid and motor oil or lubricant contained in the motor and part of the seal section. Usually, a string of production tubing supports the submersible pump assembly in the well. A drive shaft extends from the motor through the seal section to the pump.71226

Instruments to measure various operating parameter of a submersible pump assembly are commonly used. The instru- ments are normally mounted in a sub attached to a lower end of the motor. In this position, electrical power for the instruments can come from an electrical lead extending to a neutral point for the three phases of windings in the motor. The signals can be superimposed on the three power con- ductors leading to the wellhead. These instruments measure motor parameters and only indirectly pump parameter as the pump may be some distance above the  motor.

Proposals to measure parameters directly in the pump are also known, using both electrical or electronic sensors as well as fiber optic sensors. Mounting sensors within the pump, however, is a difficult task because of the length of the pump and the number of stages. Extending a sensor wire or line to the instrument sub at the bottom of the motor presents problems. The pump housing may not be thick enough for sensor wire ports and passageways  to be formed in  it.

Separate sensor wires or lines apart from the conductors 4O in the power cable for sensing electrical submersible pump assembly conditions are known. It is di8icult,  however, to route the sensor wires to various points  within  a lengthy pump.

In this disclosure, at least one instrument sub is releasably secured to one end of the pump above an intake of the pump. The instrument sub has at least one pump stage comprising an impeller and a di8iiser configured for pumping well fluid. At least one sensor is located within the instrument sub for monitoring parameters in the instrument sub. A sensor line extends sealingly through a sensor line port in the instrument sub to the sensor for conveying sensed information from the sensor to a remote instrument panel. Instrument subs may be mounted both to the upper end, to the lower end of the pump and/or between the two sections of the  pumps.

The instrument  sub has a length shorter than a length  of

the pump. The instrument sub may have a greater outer 60 diameter than outer diameters of the seal  section and  the pump. A longitudinal recess may extend along an exterior of

the instrument sub. A motor lead extending upward from the motor to a power cable locates in the   recess.

The instrument sub has a housing with a bore that is 65 coaxial with a longitudinal axis of the pump and the seal section. Rather than a larger diameter housing, the housing

the bore. The eccentric outer diameter defines a thinner wall thickness portion of the housing and a thicker wall thickness portion of the housing on an opposite side of the housing from the thinner wall thickness portion. The motor lead extends alongside the thinner wall thickness portion of the housing. The sensor line port is located in the thicker wall portion of the housing.

The dillliser of the pump stage in the instrument sub has flow passages for receiving well fluid. The sensor is mounted in one of the flow passages of the diffuser. A diffuser port extends through a portion of the dillliser. The sensor line extends through the diffuser port to the sensor. The dillliser has an annular seal mounted to an outer diameter of the dillliser and in sealing engagement with an inner diameter of the housing. A longitudinal groove is formed selectively in the outer diameter of the dillliser or the inner diameter of the housing. The groove extends from the sensor line port past the annular seal to the diffuser port. The sensor line extends from the sensor line port along the groove and through the diffuser port to the sensor. The groove is filled with a sealant to prevent leakage of well fluid