Design And Implementation Of Optical Fiber Link And Interface For Logging

Data transmission system is an important part of the logging system in the oil and gas wells, which can not only transmit real-time monitoring information from downhole to the ground, but also send the control command to downhole. Therefore, the transmission rate imposes a crucial impact on the production efficiency of the logging system. In particular, a transmission system with a higher data rate can support more logging equipments, providing improvements in estimation of oil and gas resources, productivity, and reductions in the production costs.Therefore, the development of novel and reliable transmission system for logging is one of hot topics in this field, since a full recognition of the downhole condition can provide excellent services for the oil and gas production. Recently, high-speed transmission system for logging based on optical fiber link has been put into use aboard, while relevant research and developments are just at the starting stage in China. To develop a high-speed transmission system for logging, the design and the implementation of related optical link and interface are carried out in this thesis.Firstly, several conventional transmission approaches and applications are introduced, with their characteristics and weaknesses analyzed. According to the requirements in practical applications, a high-speed transmission link system based on optical fiber link is designed and implemented, by taking both the data rate and bit error rate (BER) into account. Based on the designed system above, the optical transceiver modules, USB to serial port adapter, CAN bus module in downhole and some other modules are developed by utilizing Altium Designer6.9, respectively. For the optical transceiver modules which should be installed in the narrow space of the drilling rod, the transmitting and the receiving circuits are arranged in the same PCB board to meet the compactness of the layout structure. For the interface between the serial port of the optical fiber link and the computer (especially without serial port), the USB to serial port adapter makes the interconnection between them more convenient and flexible. By connecting the optical transceiver modules with the USB to serial port adapter, an optical fiber link for logging transmission system is established and tested. A data rate up to115.2kbit/s is realized under the high-temperature condition (i.e.,110℃). For the CAN bus among downhole instruments, a chip of C8051F04x series with with a built-in CAN controller is used for the design of the CAN bus, circuits, and hardwares by taking the stability and reliability into account. In addition, with the aid of Labview2010, the operation interface for the host computer is made, including the data acquisition and the control parts. Finally, an experimental platform for high-speed optical fiber transmission system of logging is established, such that the effectiveness of the the optical fiber link and the transmission system is verified through software and hardware tests.In conclusion, the design process and the results of the high-speed fiber transmission link and interface for logging are reviewed. Meanwhile, the development trend of the communication technology for logging and the work items to be performed in the future are discussed.