Design Of High-voltage And Acquisition Module Of The Neutron LWD Tool

Neutron Logging-While-Drilling(LWD)technology has the advantages of both nuclear logging technology and LWD technology,which can measure the hydrogen content of the formation,calculate the porosity of the formation and obtain the position of the oil layer while drilling.The neutron LWD tool is a logging tool developed according to neutron LWD technology,which is one of the most widely used logging tools in the field of petroleum exploration.The high-voltage and acquisition module is a key component of the neutron LWD tool.Its main function is to provide the high-voltage excitation power required for the neutron detector to work,and to collect and count the pulse signals returned by the detector.The neutron count rate is the raw data for measuring formation porosity and determining formation information in the neutron logging method.Therefore,the stable operation of the high-voltage and acquisition module is a prerequisite for successful neutron LWD.In this thesis,the principle of neutron LWD and the neutron LWD system are introduced firstly.The design requirements and technical indicators of the high-voltage and acquisition module are analyzed by combining the circuit structure and working process.Then,the overall scheme of the high-voltage and acquisition module is determined.Secondly,the requirements analysis and scheme design of the high-voltage DC power supply part are carried out in the thesis.The primary high-voltage circuit uses DC/AC inverter to realize the voltage conversion from DC ± 5 V to AC 200 V.Then,the secondary booster circuit,which completes 6 times voltage boosting and rectification,is designed based on the principle of the CrockCroft-Walton times voltage circuit.The stable output of 1200 V DC high-voltage is realized.Then,the design of hardware circuit and FPGA software of the high-voltage and acquisition module are introduced in the thesis.Among them,the design of hardware circuit includes signal signal processing circuit,power circuit,FPGA and its peripheral circuit,and high-voltage DC power circuit design,which are explained in detail respectively.FPGA software design includes highvoltage control logic,pulse counting logic and communication logic design,which realizes the work control and communication function of the high-voltage and acquisition module.The hardware and software design of the high-voltage and acquisition module meets the functional requirements of the module in the overall solution of the tool.Finally,a series of experiments for testing various functions of high-voltage and acquisition module are introduced,including signal processing circuit function test,neutron counting function test,high-voltage DC power supply test,high temperature and power consumption test.The experimental results are analyzed,and they show that the performance of the high-voltage and acquisition module of the neutron LWD tool meets the design requirements.