Design Of High-voltage Transmitting Circuit Of Quadrupole Acoustic Logging While Drilling Tool

Nowadays,the world is developing rapidly,and the consumption and demand of petroleum resources are also increaseing rapidly.Petroleum is an important energy source that is indispensable for national development.In order to improve the level of oil detection,the demand for logging tools is also increasing.As an important branch of logging while drilling(LWD)technology,the theoretical research of acoustic LWD logging has made a certain progress.Therefore,the acoustic LWD tools also need to be further improved and updated based on the theory.The quadrupole acoustic logging while drilling tool is independently developed in China.It is an iterative product of the monopole acoustic logging tool while drilling.It makes up for the shortcomings of the monopole instrument not being able to measure the S-wave velocity in soft formations and supports multiple operation modes such as monopole,dipole,quadrupole,etc.,with wide application prospects and high application value.The downhole hardware circuit of the instrument includes four parts: a highvoltage transmitting module responsible for exciting the acoustic transducer,an acquisition module responsible for collecting echoes,a central control module responsible for operation flow control and data processing and storage,and a communication power circuit responsible for communicating with the ground and supplying power to the acquisition module.This thesis focuses on the design and implementation of the high-voltage transmitting circuit of the quadrupole acoustic logging while drilling tool.First,the overall structure and working principle of the instrument are introduced,and the key technical points in the design of high-voltage transmitting circuit are analyzed according to requirements.The circuit is divided into three modules: control,drive and power supply,and the overall design scheme is given.The control module is mainly responsible for generating driving signals,communicating with the central control circuit and collecting voltage parameters and controlling the power switch.The hardware circuit is based on the ds PIC digital signal controller and is composed of peripheral circuits,and the control program is also designed.The drive module is used to amplify and boost the power of the drive signal.It adopts a full-bridge drive scheme.In order to ensure stable operation in a high-temperature underground environment,phase-shifting ZVS technology is used to reduce switching losses and improve circuit reliability;The excited acoustic wave transducer is a resistive-capacitive load.If it is directly excited,the electro-acoustic conversion efficiency will be low.Therefore,after analyzing the equivalent model of the transducer,a suitable transducer matching method is selected in order to improve efficiency,the sound wave energy is concentrated in a narrow frequency band as much as possible.Then,the design scheme of the power module is given,including the +5V,+15V power supply for the chip and the 80 V power supply for charging the energy storage capacitor.At the same time,the working stability of the high-voltage power supply is analyzed,and a suitable compensation scheme is designed.Then,an environment was built to perform functional tests and high-temperature tests on the high-voltage transmitter circuit.The results showing that the circuit met the design requirements.Finally,the circuit was installed in the drill collar,and the entire instrument was tested downhole.The data showing that the high-voltage transmitting circuit was well designed.It satisfies the indicator requirements.