Design And Implementation Of Telemetry System Of Integrated Instrument For Coring And Pressure Measurement

With the increasing demand for oil in modern industry,the exploration and extraction of oil is receiving more and more attention.During oil exploration,downhole geological data can be transmitted to the surface through the logging transmission system,and then the oil and gas status can be inferred from these geological data.With a full understanding of the state of the oil and gas downhole,it will be possible to extract the maximum amount of oil and thus successfully increase the efficiency of oil extraction.Therefore,the transmission of downhole geological data is of great importance in oil exploration,in order to transmit these data more quickly and accurately,a wellperforming logging system is essential.Cable logging is a common type of logging system that uses a cable specifically designed for logging to connect to logging tools in order to transmit the data collected,and it occupies a very important place in the global oil industry.In this paper,we design a cable telemetry system with strong anti-interference capability for integrated instrument for coring and pressure measurement.The system is based on OFDM modulation and demodulation technology,which enables data transmission under integrated instrument for coring and pressure measurement.The following contents are studied in this paper:1.For system communication scheme.First,according to the actual working environment and performance requirements,the communication mode,communication mechanism,modulation and demodulation algorithm,codec algorithm and cable core allocation of the system are determined.Moreover,the appropriate signal transmission frequency band is selected according to the amplitude-frequency characteristics of the cable channel,and then the data frame format of the system is determined.2.For the system design,the algorithm is mainly completed with DSP chips on the surface and downhole,combined with the algorithm complexity and working environment to determine the use of DSP chip,and then designed the implementation of other hardware functional modules.Meanwhile,designed the system communication physical layer protocols,including the design and implementation of downhole modulator and surface demodulator,state transfer during modem operation,communication timing between surface and downhole,etc.3.In terms of communication algorithm design,it mainly includes the actual realization of sampling clock synchronization,frame synchronization,channel estimation and equalization,channel analysis,channel coding and randomization and other common algorithms in OFDM system,and gives the actual test results after testing each module.Especially for the frame synchronization algorithm,two different anti-interference synchronization algorithms are proposed in this paper.Firstly,their feasibility is confirmed by simulation,and then the two algorithms can meet the performance requirements of the system through system test.