Main Control Circuit Design And Time Of Arrival Extraction Algorithm Design Of Ultrasonic LWD Imager

The most important task in petroleum exploration is to find out the reserves and location of oil in rock formations.Research on the fractures on the wellbore is an important method to explore the reserves and locations of oil.Ultrasonic imaging logging method is widely used as a safe,environmentally friendly and efficient exploration method.Ultrasonic imaging logging method transmits ultrasonic waves to the borehole wall through the ultrasonic transducer,and receives the echoes reflected by the borehole wall.Ultrasonic image can be drawn according to the time of arrival of the ultrasonic echoes.Logging personnel can judge the oil storage in the rock formation to a limited extent according to the distribution of the fractures on the wellbore wall.Ultrasonic imager while drilling is a set of combined logging tools used to image the borehole wall during drilling.Firstly,this paper introduces the research and development process of LWD ultrasonic imaging technology,and expounds the instrument structure and logging principle of LWD ultrasonic imager.Then,according to the working environment and content of LWD ultrasonic imager,this paper analyzes the functions and working modules of downhole main control circuit,and expounds each functional module in the main control circuit in detail from two aspects of software design and hardware design.Firstly,according to the actual needs of the instrument,the core control module of underground main control circuit with PIC and FPGA as the core is designed.According to the needs of communication between the core control module and the outside world,the information interaction function module is designed.The module includes the information interaction between the main control chips on the main control board,the information interaction between the main control board and the ground system,and the information interaction between the main control board and the transmitting board;The echo signal processing and acquisition function module is designed to process the analog signal of borehole echo and convert the echo analog signal into binary data;Aiming at the problem of low communication efficiency between downhole main control circuit and ground system during logging operation,a logging data storage module is designed,which uses a large capacity norflash storage array to store logging data in real time;An auxiliary information acquisition module is designed to monitor the temperature on the board of the downhole main control circuit and the amplitude of the transmitting voltage during logging operation;Aiming at the key performance parameter of echo signal arrival,the echo signal preprocessing and arrival extraction algorithms are designed.Finally,the test of each functional module designed in this paper is described.The test results show that the design meets the functional requirements of the instrument.A large number of experimental results show that the performance of the echo arrival extraction algorithm designed in this paper can meet the index requirements of the instrument.