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Publication Date: 2012-May-04
Document File: 4 page(s) / 409K

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POWER LINE COMMUNICATION techniques are described.

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Introduction / Summary \

Different Solutions have been used where a Monitoring Gauge is connected to a Wye point at the bottom of a motor, but they all have limitations (No tolerance to phase-to-ground fault, limited bit rate). The present invention proposes a solution that removes these limitations by connecting a Gauge Above the motor directly coupling the power and telemetry to 1, 2 or 3 phases.

Normally when more than 1 motor section is used, the top section has a head to connect the cable from surface. The motors below (called tandem) do not have this connection, and can be connected directly to any other motor section. The present invention also proposes the gauge to have the connection to the cable from surface (sometimes called MLE); in this solution, all the motors will be of the same type (tandem) and will be connected below the gauge.

The invention provides a method and an apparatus to transmit information from a downhole location where an electrical motor is operating to a uphole location close to the motor electrical power source, using the electrical power cable connecting the motor to the source.

In an oil well completion, a 3-phase AC electrical power source, located uphole, delivers energy through a high voltage electrical cable to a squirrel-cage 3-phase AC induction motor, operating a fluid pump. The high voltage electrical cable is normally also used as a communication channel to transmit information from a downhole monitoring gauge to the surface control unit.

Instead of using the Wye-point at motor, one, two or three phases of the cable carrying power to downhole motor can be directly used to couple the signal. This can be realized by coupling the signal at the pot-head point of the motor. This will facilitate to bypass the motor winding and hence the communication channel will be the power cable only. In the same manner a signal can be coupled at surface and detected downhole creating bidirectional communication.

High voltage capacitors and/or transformers can be used to couple and decouple the power and communication signals from the power line.

The connection to the gauge is required to be directly at the phases of the motor, and not at the Wye-point. A way to make this connection is to have the gauge connected right above the motor.

To keep reliability high by keeping only one MLE connection outside, also having the gauge as a head on top of the motors is a method of this invention Figure 1.

The downhole electrical signal source has the functions of a transmitting apparatus. It is detailed in Figure 2 and is made of:

·         One or several sensors, each converting a physical parameter to an electrical signal.

·         Eventually, a conversion of the sensor signal output to an electrical digital representation.

·         An acquisition device (e.g., microcontroller/ digital signal processor) taking samples of the sensor digital outp...