Abstract: With the development and maturation of industrial automation, the Fourth Oil Production Plant has gradually carried out automation transformation in oil production, gas production, oil transportation, and water injection, revolutionizing the production model that had been in place for decades. This article will introduce the composition and characteristics of our plant's remote monitoring SCADA system for metering stations based on our design and application experience. Keywords: metering station; remote monitoring; SCADA; iFix Introduction The Bieguzhuang work area is the main block of our plant, accounting for nearly half of the plant's total production. In order to meet the needs of precise well analysis and rapid response, and to reduce the labor intensity of employees and alleviate the personnel shortage caused by the commissioning of the new area, our plant began to implement an automatic metering project in the Bieguzhuang work area in phases in 2001. This project achieved centralized control of oil, gas, and water metering at 21 metering stations, monitoring of water volume and pressure at 21 water injection wells, and centralized monitoring of relevant parameters such as manifold pressure, temperature, and combustible gas concentration at the metering stations. 1. Composition of the Bieguzhuang Automatic Metering System 1.1 System Hardware The entire hardware system is divided into three layers, as shown in Figure 1: The data acquisition layer includes RTUs, electric three-way (two-way) ball valves and valve actuators, pressure transmitters, temperature transmitters, vortex intelligent gas flow meters, magnetic float level gauges, combustible gas alarms, water content analyzers, and other automated instruments; the remote control layer includes two remote control and monitoring servers, i.e., SCADA servers; the data analysis layer includes one data server and one client. Communication between them is via a local area network, conforming to the TCP/IP protocol. [align=center] (Figure 1)[/align] 1.2 System Software The system software architecture is divided into a data acquisition subsystem, a monitoring subsystem (SCADA), and a data analysis subsystem (DMS), as shown in Figure 2. The data acquisition subsystem is responsible for collecting data from the field instruments through various data acquisition modules (digital, analog, pulse). The monitoring subsystem is responsible for displaying the collected data on the human-machine interface, allowing operators to monitor the field situation and control the operation of the data acquisition subsystem at any time. The data analysis subsystem is responsible for storing the database, analyzing and summarizing the data, and plotting curves and graphs to help technicians analyze production and quickly identify oil wells with abnormal production. [align=center] (Figure 2)[/align] 2. The Principle and Process of Automatic Metering Based on SCADA As can be seen from the above structure diagram, the core of achieving automatic metering in Bieguzhuang is the monitoring subsystem, namely the SCADA (Supervisory Control And Data Acquisition) system. The system composition is shown in Figure 3: SCADA mainly consists of a human-machine interface program, a process database (PDB), a scanning, alarm, and control program (SAC), a drive image table (DIT), and I/O drives. [align=center] (Figure 3)[/align] Data display process: The data collected by the RTU is stored in the data register. After the I/O device polls and reads the data, it outputs it to the DIT (Driver Image Table). The SAC scans the DIT and writes the AI ​​or DI data blocks in the PDB. At this time, the SAC compares the numerical alarm setting value. If the value exceeds or falls below the alarm setting value, an alarm is triggered. Each point displayed on the graphical interface corresponds to each tag name in the PDB. The value corresponding to the tag name will be displayed on the user interface. At the same time, the SQL data (SQD) and SQL trigger (SQT) set in the PDB write the data to the data server. Hardware control process: The SCADA issues commands to write the AO or DO data blocks in the PDB (Process Database). The SAC scans the PDB and writes it to the driver image table DIT. It writes to the RTU through the I/O driver and wireless communication device. The lower-level machine commands drive the hardware actions. 3 Functions of the SCADA System 3.1 Automatic monitoring. The SCADA operating interface intuitively displays the oil measurement status of each metering station (which well is being measured, which tank is being measured, the oil level, etc.), measurement results, and the status, pressure, and temperature of each valve at the metering station, enabling real-time data acquisition, display, and storage. 3.2 Automatic Operation. During oil measurement, the system automatically performs valve-based measurement according to the well sequence number and set measurement time or number of measurements at each metering station. If no intervention is provided, this continues until all wells at that metering station have been measured and the measurement results are available. 3.3 Automatic Control. During the measurement process, measurement can be stopped. The measurement time or number of measurements can be modified after being set, and the system will act according to the latest settings. 3.4 Automatic Alarms. These mainly include safety alarms and status alarms. Safety alarms include excessively high separator pressure, excessively high concentration of combustible gas in the station, and excessively low return water temperature. Status alarms include alarms for excessively long single-tank measurement time (if a tank of oil is not measured within the specified time). Alarms are divided into two levels: high-high (low-low) alarm and high (low) alarm. 3.5 Data Management. Interaction with relational databases, data graphical display, data archiving, report generation, and data storage in the database, etc. 4 Features and Innovations of SCADA System Design 4.1 Strong System Openness and Easy Maintenance Common configuration interfaces are updated through reconfiguration. However, in order to adapt to the requirements of oilfields with continuous new areas and new wells being put into production, and continuous oil wells being converted to injection and new water injection wells, we proposed the concept of dynamic well addition and removal, and dynamic station addition and removal for the first time in the system design. Users only need to enter the name of the newly added well or station on the maintenance interface, and the system will automatically draw the corresponding process, and the operator can immediately control the well or station. 4.2 Unified Customization of System Metering Interface to Achieve One-to-Manual Multifunctionality Among the 21 metering stations in the Bieguzhuang work area, the number of oil wells in each metering station is different. The number of wells ranges from a minimum of 4 to a maximum of 17, but the processes at most metering stations are similar. To ensure a unified oil measurement interface across the 21 metering stations in Bieguzhuang and minimize system maintenance workload, a database and scripted programming were used to enable different metering stations to use the same interface for process and data switching. For stations with special equipment, the interface was uniformly designed to display or hide the equipment. 4.3 Different metering methods were determined based on the oil production patterns of different wells. Traditional oil well metering methods involve measuring a few wells per day and then calculating the total daily production. However, this method is inaccurate for wells with intermittent oil production. Therefore, we adopted a time-based metering method in our design and incorporated it into the RTU program. Timed metering allows us to determine the measurement time based on the intermittent production patterns of the wells and set it on the SCADA human-machine interface so that the well is measured within a specified time. When determining the oil production pattern of a particular well, the measurement time can be set to 24 hours or even longer, and the oil production pattern can be observed and analyzed by plotting curves. Therefore, we designed two metering methods: fixed-time metering and timed metering. 4.4 The system features real-time alarm analysis. Alarm functionality is a standard feature of almost every SCADA system, and our system incorporates real-time alarm analysis. Real-time alarm analysis analyzes alarm information across the entire system, counting the total number of alarms, confirmed and unconfirmed high-limit and low-limit alarms, and categorizing and displaying the statistical results. It also allows for alarm classification, station filtering, and sorting. Simultaneously, the system statistically displays variables that have previously triggered alarms but have now been cleared. This provides operators with a holistic understanding of the system's operation and alarm trends. 4.5 The PDB database design is scientific and rational. Given the large number of data acquisition items and the complexity of the data to be calculated, a scientifically and rationally designed process database is one of the most crucial steps in ensuring the smooth operation of data acquisition, processing, transmission, and storage. The iFIX development platform provides users with 34 database tag blocks in 5 categories. When designing the database, we fully considered the advantages of each tag block, and the selected tag blocks were the most reasonable. Data acquisition is completed by standard blocks (DI, DO, AI, AO); data transmission is completed by SQL blocks (SQT and SQD); calculated data is handled by calculation blocks (CA); delay, lead/lag, and switch control are implemented by control blocks; histograms, percentages, statistical control, and statistical data are completed by statistical process control blocks. 5. Conclusion The automatic metering system passed the comprehensive acceptance test by the expert group of the Fourth Oil Production Plant of North China Petroleum in October 2002. The system is easy to operate and reliable. The oil measurement and monitoring work of 21 metering stations was transferred to two staff members in the Bieguzhuang central control room, freeing up personnel for the new area and solving the staff shortage problem in the new area. The application of the system has changed the traditional method of manually measuring oil, gas and water, improved measurement accuracy, and reduced data errors. The system's connection with the plant's local area network enables real-time data to be published on the network, allowing technicians to view field data from their offices. This meets the needs of refined management and analysis of oil wells and improves the level of oilfield production management.