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Oil Pumping Unit RTU Data Acquisition Solution
Release date:
2020-03-31
The beam pumping unit is the abbreviated term for the beam-type pumping unit—deep-well pump oil production system, commonly known as the "nodding donkey" (due to its "donkey head" that continuously moves up and down during operation, resembling a person bowing). It is one of the most classic and widely used surface oil extraction devices in the petroleum industry.
For a long time, oil well data collection in our country has relied heavily on manual methods. Oilfield workers must travel to the site to gather production data such as dynamometer cards, balance levels, tubing and casing pressures, oil temperatures, and fluid production rates—tasks that are physically demanding. Moreover, the accuracy and reliability of this data are significantly influenced by the operators' sense of responsibility. Meanwhile, adverse weather and transportation conditions often prevent timely access to critical production parameters, severely hindering the progress toward automated management of oil wells.
Aoto Technology's NARTU product, provided for the oilfield's production area, enables real-time online monitoring of parameters such as wellbore current, voltage, wellhead temperature, pressure, dynamometer cards, current waveforms, and power diagrams. It also allows for immediate diagnosis and alarm notifications of pumping unit operational faults, supports remote start-stop control and real-time querying of operating parameters, and facilitates seamless data transmission over long distances.
Working Principle of Wellhead RTU
The wellhead RTU is the core unit of the wellhead monitoring system, externally connected to equipment such as motor frequency converters, smart meters, wireless load-displacement sensors, and temperature and pressure sensors.
RTU controls the motor’s start/stop and operating frequency via a variable-frequency drive, thereby adjusting the pumping unit’s stroke rate. An intelligent electricity meter is used to collect parameters such as power consumption, voltage, current, active power, reactive power, and power factor. A wireless integrated dynamometer measures how the suspension point load of the pumping unit changes with displacement, generating a closed curve—known as the dynamometer card—that accurately reflects the unit’s operational conditions during one complete pumping cycle, enabling diagnosis of its working status. Meanwhile, pressure and temperature sensors continuously monitor the oil pressure and oil temperature within the output pipeline in real time.
RTU provides communication interfaces such as Ethernet and serial ports. In areas with densely packed wellheads, wireless bridges are typically used to establish a local area network for communication; while in more dispersed wellhead regions, DTUs can be deployed to connect to the GPRS network, enabling data transmission.
Implementation of the RTU Monitoring System
The implementation of the wellhead RTU monitoring system not only requires addressing common issues such as data acquisition and transmission typically found in monitoring systems, but also necessitates resolving the following key challenges:
1. NARTU Platform Selection
From the working principle of the wellhead RTU, it can be seen that the RTU's internal software features are relatively complex, with numerous software modules. Therefore, a multi-threading approach is required, including threads for SCADA system communication using the IEC-104 protocol, threads for Zigbee peripheral device communication, threads for inverter communication, threads for smart meter communication, threads responsible for analog input data acquisition, as well as the main thread (handling system configuration, sub-thread creation, fault analysis, and historical data storage), and a terminal debugging and configuration thread.
Therefore, NARTU's hardware platform is built around an ARM9 core and supports a Linux-based multitasking, multithreaded operating system. The platform’s external interfaces include: a Zigbee interface, an Ethernet interface, one RS232 port, three RS485 ports, DI inputs, DI outputs, AI inputs, and VI inputs, among others.
2. Synchronization Issues in Dynamometer Chart Acquisition
NARTU supports three dynamometer data acquisition modes: the wireless load-displacement integrated mode, the wireless load plus wireless angular displacement mode, and the wireless load plus stroke switch mode. During dynamometer data collection, in addition to capturing the dynamometer curve itself, it’s also necessary to record electrical parameter curves—such as current and power curves. This necessitates addressing the synchronization between dynamometer data acquisition and electrical parameter measurement. First, the power module must be capable of acquiring continuous curves throughout the stroke cycle. Then, the RTU coordinates and ensures synchronized data collection.
Once the RTU receives the regular data from the integrated load sensor, it sends commands to both the sensor and the power module to acquire the power and energy diagrams. These commands include information such as the synchronization time, the number of sampling points, and the stroke cycle. Upon receiving the command, the instrument initiates a countdown. After the countdown ends, it captures the power or energy diagram, thereby ensuring synchronized acquisition of both the power and energy graphs.
After the sensor power curve data acquisition is completed, the power curve data blocks are immediately grouped and transmitted to the RTU. During the data transmission process, the RTU generates an acknowledgment for each data group. If no acknowledgment is received, the instrument will retransmit that specific data group up to 3 times. Once the power curve data transmission is finished, the RTU sends a command to read the energy curve data, initiating an energy curve data transmission process similar to that of the power curve.
3. Application Environment Adaptability
When considering environmental factors in oilfields, the primary focus is on conditions such as wellsite temperature, humidity, dust levels, and corrosion—factors that can significantly impact the hardware of oil-well monitoring systems. For instance, in desert oilfields located in northwest China, summer temperatures are exceptionally high, with drastic day-night temperature fluctuations, while the air contains high concentrations of airborne dust, and groundwater is rich in both salt and alkali. To ensure unmanned operation at these remote workstations, RTU designs must incorporate robust environmental adaptability features, including resistance to high and low temperatures, corrosion protection, and effective dust prevention. Moreover, the electronic chips used in the RTU's hardware platform must meet industrial-grade standards (ranging from -40°C to 85°C), and the entire RTU design and manufacturing process must include rigorous environmental testing protocols to guarantee reliability under challenging field conditions.
NARTU's Application at Oilfield Wellheads
The Qingdong 5 New Area is geographically located in the extremely shallow waters of the western part of Laizhou Bay, Dongying District, Dongying City. It consists of an 8.48-kilometer-long seaward access road stretching from the eastern city flood-control dike to an artificial island, as well as the island itself. Structurally, the area lies on the southern slope of the western depression within the Qingdong Sag. On the artificial island, all oil pumps are belt-driven units, with each wellhead equipped with an RTU control cabinet. The wellhead dynamometer data acquisition system employs a wireless load sensor combined with a stroke switch mode. The RTU controls the motor via a frequency converter, maintaining a stroke rate of approximately 0.5 strokes per minute and a stroke length of about 6 meters at the wellsite.
In the remote metering system project for oil wells, the adoption of a distributed control system and RTU technology has enabled unmanned, automated monitoring of pumping unit wells. In particular, the implementation of RTU technology has streamlined production and management processes, allowing for seamless data collection and real-time analysis of various parameters from the pumping units. This has not only provided users with the precise data they need but also significantly enhanced the overall safety and automation level of the metering system. Additionally, it has reduced the physical workload associated with manual inspections by workers and extended the operational lifespan of the equipment.
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Service hotline:+8618905163737
Company Headquarters: No. 15, Building B, Zone B, Phase I, Headquarters Economic Park, 69 Fengzhan Road, Yuhuatai District, Nanjing, Jiangsu, P.R. China
Production Center: No. 219 Qinghuiting West Road, Jiangning Economic Development Zone, Nanjing City, Jiangsu Province
Aoto Technology Co., Ltd.
