Design Of High-voltage Transmitting Circuit Of Ultrasonic Imaging LWD Tool

Known as "black gold" and "the bloodline of industry",petroleum has played an irreplaceable role in promoting the development and progress of industrial society and is an important and indispensable resource for all nations.Therefore,it is important to research new logging methods and logging instruments to improve petroleum exploration efficiency and detection level.Logging while drilling is an important logging method as it avoids the effects of mud intrusion and allows more original data to be obtained from the well wall.Logging while drilling imaging technology is an important branch of logging while drilling technology,which can intuitively reflect the situation of the well wall during the drilling process and accurately guide the drilling process of the drill collar.The ultrasonic imaging logging while drilling tool works by using the reflection of sound waves as they travel from one medium to another.The downhole circuitry processes the reflected echoes in real time to obtain information on the arrival and amplitude of the echoes,which are stored via the downhole storage circuit.The hardware circuitry of the ultrasonic imaging logging while drilling tool is divided into high-voltage transmitter circuitry,which excites the acoustic transducer to emit,and main control circuitry,which completes the acquisition and calculation of the ultrasonic echo signal and communication with other instruments.The main work of this thesis is the design and implementation of the high-voltage transmitter circuit of the ultrasonic imaging logging while drilling tool,which focuses on the following aspects.I.The design of a high voltage and high frequency emission drive circuit which can output a transducer excitation voltage of up to 200 V peak-to-peak and has a transducer excitation frequency of 250 k Hz.A high voltage power supply circuit and a MOSFET driver circuit are built to excite the transducer.A transducer tail vibration removal circuit is designed to reduce the effect of tail vibration on the measurement.And a transmitter circuit power supply control design is incorporated to reduce the overall power consumption of the circuit by cutting off the power supply to the circuit when the high voltage high frequency transmitter circuit is not operating.II.The design of high voltage and low frequency transmitter driver circuit.This part of the circuit consists of a boost circuit and a full-bridge drive circuit constructed by IGBTs.The peak-to-peak excitation voltage at both ends of the acoustic transducer in the circuit can reach 2000 V,and the frequency of the transducer drive signal is 25 k Hz.The boost circuit consists of a full-bridge inverter circuit,a transformer step-up circuit and a rectifier filter circuit.The excitation pulse of the transducer is obtained under the combined action of the full-bridge drive circuit with the drive signals generated by the controller.In order to ensure that the transmission efficiency of the drive circuit and the excitation voltage at both ends of the transducer meet the design requirements,an impedance matching circuit is designed.III.The design of the control module for the transmitter circuit of the ultrasonic imaging logging while drilling tool.The control module that consists of the ds PIC microcontroller and its peripheral circuits is responsible for the generation of the transducer drive signal,the communication with the main control circuit,and the control of the power output.And the control program for the high voltage transmitter drive circuit is also designed.IV.Set up a test environment in the laboratory for the high-voltage emission circuit of the ultrasonic imaging logging while drilling tool and test the high-voltage emission circuit.The test results show that the modules of the high-voltage transmitter circuit are working properly and meet the expected design requirements.