| With the development of science and technology,the demand for energy in various countries is increasing,and oil and gas resources account for the main part of energy,so the exploration of oil and gas resources is very critical.Well logging technology is an important technical means for oil and gas resource exploration.Compared with wireline logging,logging while drilling(LWD)is more suitable for complex terrains.It can measure formation information while drilling,and has less damage to formations.Therefore,in oil and gas In the field of exploration,the status of LWD is becoming more and more important.Based on the project “Development of Acquisition and Storage System for Omnidirectional Acoustic Wave Train Signals While Drilling”,this thesis researches,designs and implements a main control system of an omni-directional wave train acoustic logging tool while drilling.The all-round wave train acoustic logging tool while drilling can measure all-round acoustic signals downhole and comprehensively analyze formation information.The main work of the thesis is as follows:(1)Carry out the overall design of the main control system and specify the design indicators.The main control system mainly includes a main control module and a storage module.The main control module is responsible for controlling data storage and communicating with other parts of the instrument and the upper computer as a communication center.The data storage module is responsible for the storage of acoustic logging data and auxiliary information? the design indicators cover Communication rate,temperature measurement accuracy,data storage module capacity and maximum operating temperature,etc.(2)In order to solve the problem of inter-board communication and storage control at high temperature,multiple sub-modules are designed in the main control module with DSP processor as the core,including multi-channel communication sub-module,power supply sub-module and temperature measurement sub-module.Methods such as the use of large pads are used to solve the problem of heat dissipation at high temperatures.In order to control the acquisition timing independently,the corresponding acquisition control process is designed.(3)In order to store a large amount of different types of logging data,the Nor Flash storage sub-module for storing non-omnidirectional wave train acoustic logging data and auxiliary information,the NAND Flash sub-module for storing omni-directional wave train acoustic test data and Extended storage submodules for storing large arrays and variables.According to the difference of the memory chip and data,the corresponding underlying driver,memory reading process and power-on positioning algorithm are designed to solve the address positioning problem when the system is powered on again after poweroff.In order to solve the problem of data verification and error correction and the reduction of the service life of the data storage module due to the different frequency of use of memory chips,the error correction verification algorithm and wear leveling algorithm were studied,and the Hamming code as the core was designed according to the actual situation.ECC check error correction algorithm and wear leveling algorithm suitable for data storage modules.(4)The main control module and the data storage module were tested,and the test results showed that the communication rate of the multi-channel communication sub-module with the acquisition control board,the launch control board,the ground control system and the Port port can reach 625 Kbps,40Kbps and 1.04 Mbps respectively,the measurement accuracy of the temperature measurement sub-module can reach ±1°C,and the poweron positioning algorithm,calibration and error correction algorithm can all realize their functions? at the same time,at a high temperature of 150°C,the main control module and data storage module can run for a long time(up to 120 hours),which meets the design requirements. |
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