| In the oil industry,well logging technology in multiphase flow measurement is an important means of reservoir dynamic monitoring,which can provide geophysical logging information for reservoir management and optimization of oil well production performance.The booming transmission data of well logging sensors used in multiphase flow measurement demands higher transmission rate and its quality in logging technology with wireline data transmission.However,the characteristics of narrow effective bandwidth,selective fading and interference by extremely high temperature and pressure environment of the single-core logging cable,which results in unpredictable performance in the transmission rate and transmission quality.In addition,the problems of logging hardware in the transmission equipment such as complex circuit,high power consumption and difficult data exchange among modules reduces the transmission reliability.Hence,the study of data transmission system of well logging sensors used in multiphase flow measurement with high-speed and stability is of great significance to the improvement of well logging technology for real-time monitoring and efficient production of oil field exploitation.This study designs and realizes the data transmission system of well logging sensors in multiphase flow.The cable distribution parameter model is established to analyze the transmission characteristics of single-core cable.On this basis,the data transmission algorithm based on Orthogonal Frequency Division Multiplexing(OFDM)is studied and the transmission performance among different modulation-demodulation algorithm is compared and analyzed.In addition,the hardware and software of data transmission system is designed and the OFDM data transmission algorithm is realized based on the hardware architecture of dual-core Digital Signal Processor(DSP).Combined with the measurement platform of multi-phase transfer sensing system,the data transmission simulation device of well logging sensor is set up to test and analyze the signal transmission performance of multi-channel signals of the rotating electric field conductance sensor with eight electrodes.Innovative research results of this thesis are as follows:1.When comparing with the traditional domestic logging transmission system,the hardware architecture based on dual-core DSP not only reduces thecommunication difficulty between control module and signal processing module,but also simplifies the hardware system complexity which can reduced the power consumption and system volume size.2.According to the characteristics of single-core cable,the key technologies such as 16 QAM subcarrier modulation-demodulation and Cycle Prefix are adopted,and Time-domain equalization algorithm is combined with Frequency-domain equalization algorithm.Therefore,the transmission system effectively improves the data transmission rate and anti-disturbance level.3.The designed data transmission system of well logging sensors is utilized to carry out the transmission test using the actual signals of oil-water two phase flow well logging sensing system.The results show that the rotating electric field conductance sensor’s signal transmission error rate is less than 1% at transmission rate of 280 kbps under 7000 m simulation transmission,which indicates good hardware and software design results. |
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