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Oil production with sucker rod pumps (here and after referred to as SRP) is the most common way to lift oil. This is due to their simplicity, efficiency, and reliability. At least two-thirds of active production wells are operated with SRPs.
The cornerstone of oil production is to maximize production while reducing electricity costs. The installation of Triol’s variable frequency drives with downhole controllers can solve both issues.
Triol offers the user two variable frequency drive lines for controlling the SRP downhole controller:
SR line
- Hinged cabinet with IP55 degree of protection;
- Main circuit breaker;
- Variable frequency drive;
- Heating and ventilation system for open air operation;
- Intelligent downhole controller with a 3.5'' or 5'' touch screen;
- GSM/GPRS modem with remote antenna and web service for remote monitoring and configuration;
- 3f + N panel outlet with circuit breaker for power supply to other devices.
RT line
- IP54 or NEMA3R rated cabinet;
- Main circuit breaker;
- Variable frequency drive;
- Heating and ventilation system for open air operation;
- Intelligent downhole controller with 3.5" or 5" touch screen;
- GSM/GPRS modem with remote antenna and web service for remote monitoring and configuration;
- 3f + N panel outlet with circuit breaker for power supply to other devices.
The following options can be optionally installed in the cabinet:
- Braking chopper and braking resistors;
- Main choke or passive filter to reduce influence of VFD on mains;
- Filter dU/dt or the sine-wave filter to protect VFD windings from peak overvoltages occurring during operation with VFD;
- Bypass circuit for switching the motor of the SRP independently of the VFD.
Our challenges when developing VFDs for SRPs:
1) Reduction of equipment cost;
2) Ease of use;
3) Increased well flow rate due to unique algorithms in the controller software.
Thanks to the unique algorithms developed by Triol Corporation, when operating with a 4-quadrant load, the VFD monitors the current motor frequency and avoids the transition to the generator mode. In regenerative mode, energy is stored in the DC-link of the VFD and can lead to an emergency stop. To avoid an emergency stop, braking choppers in the DC link and braking resistors are used to dissipate the surplus energy.
The algorithms used in the SR and RT VFD lines removes the need to use braking resistors, on which the excess energy from the DC link of the VFD is dissipated in the generator mode of motor operation, which leads to a saving in the SRP’s energy consumption.
Due to the automatic filling level control of pumps, for wells with inconsistent flow, high gas content, etc., additional energy savings are achieved by controlling the number of pumping operations (motor speed).
The same economy is achieved through the smooth motor start-up, without motor starting currents, which additionally reduces the load on the pump rod and motor gearbox.
The author's algorithms of the SRP’s downhole controller allow the building of dynamograms without using a polished rod load cell. Installation does not require the installation of this sensor – it saves time. No purchase of the load cell itself is required – a direct money saver in the implementation of the VSD for SRP. The error that was achieved in the sensorless mode of building dynamograms was less than 2% of that which is given using the sensor.
Dynamograms taken with the sensor (left) and the constructed SR line of the VFD without using a sensor on the same well.
The VSD SRP controller is equipped with a microSD card flash drive, which records the current parameters of the equipment, as well as dynamograms created during well operation.
Dynamograms and parameters can be "uploaded" to the flash drive to view them on a PC, as well as being viewable on the screen of the built-in PLC, which allows the user to quickly determine the condition of the equipment and, if necessary, adjust the operating parameters of the VSD SRP.
Display of several dynamograms on one screen.
The setting of variable frequency drive parameters, input of SRP parameters, and control of the equipment is performed using the touch screen display of the downhole controller. No additional monitoring or set-up devices are required for start-up.
The VFD equipped with intelligent well controller can operate in two modes when operating in automatic mode:
- «maintaining fill level» – in this mode, the VSD SRP regulates the number of pumping operations per minute to ensure the fill level of the pump specified by the user;
- «production maximization» – in this mode, the VSD SRP regulates the number of pumpings per minute to ensure the maximum production level of a particular SRP, taking into account its specific features (geometry, gas availability during pumping, paraffin deposits, and other factors affecting operation of the equipment).
Example of operation of the VFD AT24 SR line on a well in the "maintaining fill level" and "production maximization" modes.
