Development Of Launch And Detection Circuit For High-Temperature Ultrasonic Imaging Logging Tool

Ultrasonic imaging logging tools are commonly used in cementing quality testing.They can evaluate casing damage and cement cementation quality.Compared with other traditional instruments,they have the advantages of rich logging information,high resolution,and easy analysis.With the increase in the number of high-temperature oil and gas wells,the development of high-temperature ultrasonic imaging logging tools has become a focus of research in recent years.Aiming at the problem of pulse emission and signal detection in high temperature environment,this paper designs the launch and detection circuit of high-temperature ultrasonic imaging logging tool.The circuit mainly includes: receiving amplifier circuit,pulse transmitting driving circuit and pulse triggering and high-speed acquisition circuit.It realized the functions of pulse signal transmission,ultrasonic signal reception,data acquisition and processing under 175? environmentFor the ultrasonic imaging logging tool receiving amplifier circuit working in a high temperature environment,as the temperature increases,the bias current will interfere with the circuit due to the internal resistance of the asymmetric source,and the circuit performance will also decrease.Designed low noise instrument amplifier circuit?bias temperature current compensation circuit?variable gain amplifier circuit and filter circuit.The experimental results show that the circuit has good frequency response and linearity in the temperature range of 25?-175?,and the circuit has high temperature stability.The pulse emission driving circuit needs to transmit high voltage signals,and the circuit has a large working power,which can easily cause the device temperature to rise sharply in a high temperature environment and the circuit will be damaged.Designed power amplifier circuit,high voltage power circuit and motor drive circuit to achieve the function of pulse transmission.And the thermal design of the high-power devices in the power amplifier circuit is improved by adding a heat sink.The simulation and measured data show that the pulse emission drive circuit can emit pulse signals that meet the requirements and can work stably at a high temperature of 175 °C.Digital circuits in high temperature environments may cause the circuit to malfunction due to device temperature performance limitations.Designed a high temperature resistant pulse trigger and high-speed acquisition circuit.The circuit designed an A / D acquisition circuit with FPGA and DSP as the control core.Embedded software part designed signal processing flow such as digital filtering,parameter extraction,gain control and data transmission.And designed the circuit-level thermal design for the high-temperature working environment of the circuit.The test results show that the circuit can work in a high temperature environment downhole,meet logging requirements,and can be used in practical engineering.