Design Of High Temperature Petroleum Logging System Based On PLC

Measurements operation of colleting down-hole environmental parameters requires us to collect data from 2000 meters to even 7000 meters of subsurface and transmit data back to the ground.Due to the specialty of the environment,petroleum logging system always works in an extreme environment of high temperature,high pressure and high airtight.Besides,the cables used in a petroleum logging system,neither the single-core cable nor the seven core armored cable were initially designed for data transmission.Considering the rigorous signal transmission condition and the low transmission speed,how to realize an accurate down-hole data collection in this kind of harsh environment has become the focus of the engineers' research.In this paper,collaborate with the power line carrier communication technology,the author implements a system for over 3000 meters subsurface environment down-hole data collection and transmission to realize the down-hole data collection and transmission under environment of 200 Celsius degrees.Firstly in this paper,I introduces the background of the research,elaborates the power line communication and petroleum logging system's present situation and develops an research program based on single-core power line carrier communication transmission for data collection and transmission.After that,focus on power line communication technology,this paper analyzes its classification,impedance characteristics,attenuation and noise characteristics in detail for single-core power line carrier communication channel model establishing.The simulation results reveals single-core power line communication channel's amplitude-frequency characteristics and phase frequency characteristics,which provide the basis of the system design.In order to improve the reliability and accuracy of the system,this paper introduces the signal modulation technology.After comparing both advantages and disadvantages of power line communication between using OFDM technology and using spread spectrum technology,this paper chooses OFDM technology as this subject's Modulation and demodulation technology.For OFDM,this paper analyzes its technical principle and mathematical expressions,and then briefly introduces its IDFT realization,guard interval and cyclic prefix technologies.With the comparison of several common digital modulation modes,this paper selects DPSK as the digital modem scheme of the system.Combined with power line communication technology,this paper realizes OFDM technologyin single power line communications,and achieve the power line carrier communication's overall design for this project.Based on this design,this paper generates the overall hardware solution,introduces above-ground part and underground part's modules features separately and gives the schematic design.After hardware section,this paper focuses on introducing the software compensation algorithm applied in this project,analyzes the requirement of the software algorithm and completes large amount of calibration experiments.With the analysis on the experiments data using LabVIEW,this paper generates an appropriate sensor compensation algorithm for this project.Finally,all the modules are cooperated together and this paper makes great amount of test.In the very end,a conclusion and future prospects of the system's deficiencies are given.