Research On Some Key Issues Of High-speed Wireline Logging Networks

With the rapid development of modern industry,the demand for oil in the human society has shown an increasing trend. The logging is one of the important stages in the process of oil exploration. The logging transmission system is used to transmit logging data from the down hole to the surface through the appropriate means of communication. The performance of the logging transmission system is one of the key factors,which influences the efficiency and quality of the logging. In recent years,research and design of fast,real-time,accurate logging transmission system is an important direction of development.There are several kinds of means for logging data transmission, such as mud, drill string, fiber, and wireline.Due to the good stability, long transmission distance and other beneficial factors, the wireline remains the main means of logging transmission. As an effective wideband modulating technology, the OFDM (or DMT) is used to improve the transmission speed of the long well logging wireline in recent years. Networked measurement and control system can connect devices more conveniently with good interoperability. In nearly 20 years, some results have been achieved in the research of network control system, and network control system is used in many fields, such as product line in factory. However, the networked system for whole logging transmission is staring at present.We discovered that the logging network is a network focusing on measurement,which needs to acquire accurate data and record the corresponding measurement parameters,such as time,depth,and length. OFDM modulation techniques can improve the rates of cable, and also increase the network transmission delay. The IP packet switched network is a best-effort service network, and don't provide assurance in real-time transmission. Thus, long delay and high jitter are disadvantages for networked logging transmission system.In order to solve these problems, this dissertation presents a time-driven logging data transmission method used in a full IP logging network. The method needs all the nodes in the network to keep accurate time synchronization. The depth acurquied on the surface and data acurquied in downhole equipment is fused based on synchronized time parameters, and then logging curve is obtained. This method is not sensitive to the delay of logging the network. Even in the long-delay network, this method also obtains accurate logging data.In the first chapter, several existing logging transmission mode are described. The current status and development of foreign and domestic technology of logging transmission are introduced, and the development of cable transmission system is analyzed. In second chapter, the framework and characteristics of high-speed wireline logging networks are described at first,including the well logging instrument buses,wireline cable modulation coding method and the logging curve interpretation.The second chapter also describes the framework and components of logging network using IP packet switch, and the theory and data model based on time-driven method. In last section, a preliminary analysis of key issues is presented, including network traffic characteristics, the router queue management method, logging the network time synchronization, and data fusion method.In the third chapter, we give an introude to the basic theory of network traffic modeling, point out that network traffic has a multi-dimensional characteristics, which means that network traffic is relative to the scale of observation time, the protocol layer, application service type,the area and type of network,and network load,etc.. In chapter III, we also focuses on analysis of network traffic logging features, point out that the logging network traffic has periodicity with light-tailed distribution. Simulation results show that traffic on the network layer has similar characteristics of the Poisson distribution. In the last section of the third chapter, we give the main parameters of OFDM modulation, and discussed the impact on network transmission from bottleneck (asymmetric) link with asymmetric bandwidth.In chapter IV, queue management methods in logging router and the optimal method of logging the router are discussed. First of all, we give a review the basic theory of the router, and analyze the characteristics of logging router. Secondly,we discusse the allocation method in the shared buffer mode,and proposed the QMBPS method for queue management in logging router. The QMBPS considers the packet size, queue type, and packet type to improve the bottleneck link utilization,and reduce delay and jitter of short packet,especially ACK packet. The QMBPS gives a priority to packet in the queue by a priority function, and processes all packets in accordance with high or low priority. In chapter IV, optimization method for logging router is proposed to decrease the routing search time and improve the transmission efficiency of the bottleneck link. The time synchronization method for logging network is studied mainly in the chapter V. First, the theory of network time synchronization is analyzed. The relationship between jitter of roundtrip delay and synchronization time offset is obtain. Based on the analysis result of characteristics of each component in one-way delay, we discover that the accuracy of network time synchronization can be improved by reducing the delay jitter. Secondly, the logging networks uses time synchronization method by subnet to avoid frequent time synchronization data to increase the load on the bottleneck link. The modem in down hole is a root reference clock, which provides reference time to downhole instruments and surface modem simultaneously. The surface modem provides synchronized time to other surface equipment. In chapter V, we focuses the study of time synchronization using CSMA/CD shared Ethernet subnet, and propose a selective time synchronization method using hardware timestamp to reduce delay jitter resulted from operating system and buffer. A selective switch for ordinary data frame and frame data is set in low layer to reduce unprecticalble jitter from accessing CSMA/CD. Theoretical analysis and experimental results show that the method is effective and can obtain high precision time synchronization in different network load.In chapter VI,the fractal theory and fractal interpolation method are discussed. According to the fractal characteristics of logging data and real-time requirements of data fusion,this dissertation presentes a new method used to extract sub-logging data with sentencing guidelines of the accumulation of partial Kurtosis,and in the extracted data segment,self-affine method is adopted for rapid interpolation. The simulation results show that the method is effective.The chapter VII gives the design of experimental platform for cable logging high-speed network and business layer data encapsulation. Chapter VIII illustrates the experiment and result analysis, and then gives the summary and outlook of this dissertation.For a networked transmission system of logging, it is an equal emphasis on theoretical research and engineering design. Based on the combination of OFDM modulation techniques used in the telemetry cable and IP packet switching technology used in full logging networks, logging data transmission method based on time-driven in a full IP network is given. That the theoretical analysis is consistent with the simulation result, and the result of examination in testbed shows that these methods are effective. The theoretical methods and technical means presented in this dissertation, not only can be directly used to study and design the cable logging high-speed network system, but also has certain reference values in modeling analysis of other telemetry control network.