A Design And Realization Of The Master Control Circuit Of Through-Bit Multi-pole Array Acoustic Logging Tool

Multi-pole acoustic logging is a commonly used geophysical logging method,which can identify underground reservoirs,analyse formation anisotropy and evaluate reservoir fracturing.However,in order to improve oil and gas recovery efficiency,large deviated wells and horizontal wells have been widely used in major oilfields at home and abroad,which leads to the inability of conventional cable multi-pole array acoustic logging tools for effective measurement.Therefore,the research and development of a through-bit multi-pole array acoustic logging tool with independent intellectual property rights and suitable for large deviated wells and horizontal wells has important engineering practical significance.According to the engineering application requirements of the through-bit multi-pole array acoustic logging tool,the basic functions and working modes of the downhole master control circuit are analyzed,and the design scheme of the downhole master control circuit based on the structure of "FPGA + DSP" is proposed.According to the requirement of real-time storage of downhole acoustic data,a 16 GBytes downhole data storage scheme based on Nand Flash is adopted.In order to meet the requirement of transmission rate and anti-interference performance for data transmission between master control circuit and acoustic acquisition strip,four LVDS(Low Voltage Differential Signal)interfaces for parallel transmission are designed.In order to solve the problem of long time to read mass storage data,a USB interface with theoretical communication rate of 60MB/s is designed.After the development of the master control circuit,the function and performance are tested.The test results show that the master control circuit can stably and reliably control the acoustic emission module and the acoustic acquisition strip to complete the acoustic exciting,signal acquisition,data storing and data reading according to the predetermined process.The main innovations of this paper are:1.High integration.Based on the structure of "FPGA+DSP",all fanctions of the master control,processing,storage and reading for through-bit logging is integration into a PCB with a width of 40 mm and a length of 300 mm,which satisfies the requirements of multi-function and miniaturization of the master control circuit for through-bit multi-pole array acoustic logging tool.2.Downhole large-capacity storage.A large-capacity downhole data memory based on Nand Flash is designed and implemented,which provides the storage space of logging data for 7 hours.The working temperature of memory chip is respectively125? and 160? before special packing and after,which meet the demand of downhole storage for multi-pole array acoustic logging.3.Design a new USB2.0 communication interface.In order to shorten the time of reading logging data on the ground after lifting up the instrument,the USB2.0communication interface of the instrument was designed and implemented.Its speed reached 20MB/s.Compared with the conventional RS-232 interface,the transmission rate increased by nearly 1400 times,and the working efficiency of the instrument was improved.In summary,according to the actual needs of the project,this paper designs and realizes the master control circuit of the downhole,solves the key technical problems of the through-bit multi-pole array acoustic logging tool,provides a feasible solution for the development of the through-bit multi-pole array acoustic logging tool,and has reference value for the development of other storage logging tools.