What is a permanent downhole gauge (PDG)?
A permanent downhole gauge is a recording device permanently installed in a well to monitor the parameters of the reservoir. Typical permanent downhole gauges measure pressure and temperature, but can also measure parameters such as vibration, flow, or strain.
Permanent downhole gauges are mostly installed on the production tubing in oil and gas wells, but can also be used in water wells, disposal wells, mineral extraction wells, mining safety or gas storage applications. Permanent downhole gauges can be installed as a single gauge or multiple gauges on a single TEC cable.
Sampling rates for the data can range from multiple times per second to once per day, depending on the application. Different accuracy and resolution specifications can be chosen to suit the desired outcome of the data, but the better the measurement device, the higher the cost. Higher accuracy gauges are used for precision reservoir calculations and modelling, whereas lower precision gauges are used to detect liquid levels for pump control.
Different housing materials can be chosen to handle the corrosive effects of the fluids in a well.
A permanent downhole gauge (PDG) consists of:
- A downhole sensor/transducer
- Circuits for control, telemetry, power, and measuring the sensor
- A housing
- Electrical connectors to connect to the power and communication systems
- Seals to keep the well fluids out of the gauge.
Permanent downhole gauges are used as part of a larger permanent monitoring system which consists of:
- A surface recorder (to communicate with the downhole gauge(s), store data, communicate to control systems)
- Production tubing
- Cable clamps/collar protectors
- TEC wire/tube wire/cable
- Gauge carrier
- Splices (when needed)
- A Cablehead
- Permanent downhole gauge (PDG)
- Wellhead outlet/exit
- Power system
- A communication system (SCADA)
- Spooling unit (spooler)
DataCan designs and manufactures quartz transducer-based gauges and piezo-resistive sensor-based permanent downhole gauges. Quartz permanent gauges have higher costs, but give better maximum temperature rating, lower sensor data drift, and higher sensor resolution.
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