Digital Oilfield Construction In The Design And Implementation Of Remote Measurement And Control Terminals

The Remote Terminal Unit(RTU) is also called a Remote Measurement and Control Terminal or Remote Terminal Control System. Based on RTU design differences of each company, the functions and realization methods are not same. Today, among the RTUs which are applied to oil fields, some only have the functions of data transmission, and some have measurement functions, and some have control functions at same time. The most of these RTUs are transformed from general RTUs and cannot meet the need of oil fields.Through extensive investigation and research, in view of existing problems, concerns, and the actual demand on oil fields, the designs of the RTU of this paper are focused on the following five aspects: communication, data acquisition, remote control, equipment protection, intermittent pumping and Engineering drawing diagnose.In communications, the early oil field equipment does not have the communication function(now, most oil wells, water injection wells, water wells, metering room and united stations do not have the communication function yet). All instruments are required to inspect and read by staff, data acquisition is not timely, it is difficult to obtain early warning data. Say nothing of fault pre judgment and prevention of accidents. Later, wired communication mode appeared in oil field(the way of communication with RS485 interface), but because the wiring is required, this method of remote communication has high cost and is not convenient in maintenance for a wide range of equipment of oil fields, therefore it is not widely used, and is used usually only in well local communication. With the development of Internet technology, especially the development of wireless Internet technology, wireless Internet technology provides the possibility for the construction of digital oil field. Communication design of this RTU of the paper is based on Internet technology. Between the RTU and the master station, IPv4 and IPv6 dual protocol stack are used in order to meet the different environment needs of every user. The Communication between RTUs is based on IPv4 protocol, for convenient of configuration of user application. The Communication between RTU and instrument make use of the micro power wireless communication technology, for the aim of prolonging the replacement cycle of powered battery in open country.The main quantity which oil fields need to collect include switch state, flow, pressure, temperature, load, displacement, flow rate and the AC analog. The characteristic is that the precision requirement is not very high, but the numbers of collected data are large, such as oil pressure, casing pressure, wellhead back pressure, oil temperature, oil wells stroke, speed, load, and the working voltage, current, power of the motor and so on, and other dozens of physical quantities. For measurement room, the collection numbers of data are much more, for only one temperature is often as more as dozens. Therefore, the design of the RTU quantities must be able to capture more multiple physical quantities, and has scalability.Remote control is a new remote operation method of communication. In order to solve the fault of equipment, avoid expansive losses, most of the equipment controls are run automatically. Therefore, remote controlled operation needed is not much. For example, the controls of an oil well include 3 points: one is the remote start and stop well control; two is the voice alarm control; three is the light alarm control.Equipment protection namely means the auto control actions of the RTUs in order to avoid further loss or failure when there is fault equipment or some data beyond the normal value. Taking into account the stringent real-time requirements in oilfield equipment for data acquisition, remote control, equipment protection, the RTU of this paper uses the u C/OS-II real-time operation system, instead of non-real-time traditional Linux operating system. The speed of the RTU acquisition, processing, response gets to millisecond.General RTU has no intermittent pumping control function. The RTU of this paper designs two kinds of intermittent pumping function for energy saving and reducing the loss of equipment. In the multi-rate area, energy saving pumping control can be used. By considering the well production and local electricity price fluctuations, the oil pumping time can be arranged at a lower price time, and it can greatly reduce the operation cost of the oil field. In the non-multi-rate area, only the pump full coefficient is needed to consider, and simple operation of the intermittent pumping control function can be used to realizing energy saving.Indicator diagram is very important for the oil field. At present, the most of RTUs in oilfield can only realize the load and displacement synchronization acquisition, but the acquisition of current and power cannot meet the requirements of synchronization. Individual companies do the collection of current and power figure. And electric energy data acquisition only uses a meter module or a 485 serial interface electric energy meter. The serial port communication acquisition leads to two problems: 1, the acquisition time cannot be true synchronization; 2, power meter module is based on the DL645 protocol to display on the forward and reverse power respectively, while the RTU producers only collect the positive active power, resulting in power always displaying 0 during pumping unit stroke discharge, not reflecting the actual working conditions of pumping unit, and this is obvious in the plateau machine. The RTU of this paper build directly the electric energy acquisition circuit and indicator diagram application, collect load, displacement, current, power. Thus the RTU ensures the consistency of the sampling time. This makes the diagram diagnosis develops from theoretical analysis to practical application level.