| The real-time monitoring of down-hole temperature and pressure parameters is of greatsignificance to realize the reservoir characteristics and understand the reservoir developmentperformance. It is also of great importance to analyze the oil and gas reserves and theirdistribution, to evaluate the production statement and oil well age-size. The key to achieve thereal-time monitoring of down-hole temperature and pressure lies in the reliable informationtransmission between bottom hole and ground surface. The down-hole data wirelesselectromagnetic transmission system studied in this thesis is a combination of down-hole datashort distance wireless transmission technology and electric cable based surface read-outtechnology. With the help of this system, we are able to monitor the temperature and pressureinformation of the lower part of down-hole shut-in tool under well shut-in condition. And thissystem will improve the measurement accuracy and signal transmission stability evidently,which is of remarkable technical and economic significance.In this thesis, we firstly analyze the system transmission characteristics under differenttransmission distance, different tubing and casing diameters, different annular clearance,different wall thickness and different annular medium electric resistivity with the help ofAnsys. According to the analysis results, we determine the parameter range of the down-holedevice mechanical structure.Then on the basis of ground simulation experiment platform, the voltage-frequencycharacteristic experiment is finished and the frequency band under which the signal willtransmit stably with less attenuation is found. The attenuation multiple is also known. Theexperiment results will provide data support for the design of the circuitry system.The signal generator, signal receiver and electric cable based surface read-out system are designed according to the ground experiment results. The signal generator will collect thetemperature and pressure information and transform them into sine wave with differentfrequencies. The sine wave will drive the transmitting coil after amplification. We designsignal generators separately on the basis of ICL8038and MCU. The signal receiver willamplify the small-signal detected by receiving coil and then transform the sine wave intosquare wave. The MCU will measure the frequency value of the square wave through lowpower timer function. The electric cable based read-out system will achievetelecommunication between two microcontrollers through CAN communication protocol. Theelectric cable based read-out system is used to monitor the electric cable communicationbetween bottom hole and ground surface.On the basis of circuitry system, we draw out the PCB boards according to the circuitdesign scheme. The down-hole power supply source and temperature sensor are chosen. Andcombine with the Ansys analysis results we work out the transmitting mechanical joint andreceiving mechanical joint. Their function is supporting the magnetic core coils, the circuitwafers, the down-hole power supply source and the sensor. Finally, the overall design schemeof wireless electromagnetic short transmission system was achieved. |
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