Design Of Downhole Main Control Circuit Of Quadrupole Acoustic Logging While Drilling Tool

Logging while drilling(LWD)technology has unique advantages and has developed rapidly in recent years.It has become an important branch of logging technology.Compared with wireline logging technology,LWD tools measure formation information while drilling operations.At this time,the formation damage is minimum by the outside world,and the logging data can record formation characteristics more accurately.The design of quadrupole acoustic LWD tool is a sub-project of the national major scientific and technological project "Development of large oil and gas fields and coalbed methane".The purpose is to design an advanced acoustic LWD tool which can realize combined logging with multiple acoustic source modes.The downhole main control circuit board is the control center of the quadrupole acoustic LWD tool,as well as the data processing center and data storage center.It connects the downhole acquisition board and the transmitting transducer and the ground control system.Aiming at the hardware connection characteristics of downhole main control board,multi-channel board-to-board communication is designed.Aiming at the multi-mode acquisition characteristics of quadrupole acoustic LWD tool,the acquisition process control program and data processing program are designed.The data transmission between downhole instruments and ground system is carried out by mud pulse,and the transmission efficiency is very low.The logging data can't be uploaded to the ground in real time.So a mass storage module is designed to ensure that the logging data are stored safely and reliably in the downhole circuit system.and the time difference extraction algorithm is transplanted to the DSP platform to realize.In this thesis,the instrument structure and logging principle of the quadrupole acoustic LWD tool are briefly introduced.Then the overall design of the downhole main control board is described,and the key and difficult technologies in the design are put forward.Next,the function modules of the downhole main control board are analyzed in detail from two aspects of hardware design and software design.According to the function requirement of downhole main control board,the hardware circuit with DSP processor as the core is designed.The peripheral circuit includes multi-channel communication interface module,memory chip array module and auxiliary information measurement module.According to the power requirement of the circuit,a power module is designed to meet the power requirement of the system.The thesis focuses on the program design ideas and implementation methods of five key modules: multi-channel communication module,acquisition process module,auxiliary information measurement,downhole time difference extraction algorithm transplantation and mass storage module.At the end of the thesis,each module is tested,and the test results are analyzed to prove that the downhole main control board achieves the design target.