Design Of Down Hole Formation Resistivity Parameter Acquisition And Transmission System

Raw data of formation resistivity can be obtained in various ways, including array laterolog technology which was evolved from dual laterolog. As one of the focused logging technology, it can significantly reduce the impact of factors like flushed zone and adjacent formation on apparent resistivity, and provide curves with different depths of investigation. These are of great help to judge invasion character and it's more suitable for well logging in thin layer and permeable formation, thus been widely used. Rarely does domestic companies have such kind of instruments, so continuous research is of important significance and value on the basis of previous work.Under the background of the design of laterolog array tool prototype, it brings great challenge to design logging system in view of its special working environment and complex processes such as data acquisition, transmission and processing.This article started from the current development status and basic principles of laterolog array well logging, hardware circuit was divided into several functional units according to data flow and take the whole system into account. On the basis of these units, completed the software part of main controller and communication circuit of the tool system. This part contains the implementation of reading and preprocessing of raw logging data, automatic gain control of transmit signal and copying function of initialized sections. Among these functions, in order to decrease the pressure on the telemetry system, introduced the digital phase sensitive detection algorithm to preprocess the raw logging data which reduced the amount of data greatly and satisfied the requirements. Distortion of the emission source may occur when the differences of well conditions considered, use the calculation result of the same algorithm to realize the judgment of distortion state of those signals, thus completed the automatic gain control of the emission source instead of manual control. Copying function of the initialized sections for optimizing DSP program execution time was added to the program to against the situation——the amount of the computations of the DSP is large and processes such like data read focus on the interrupt service routine which may be interrupted. This function will copy all the initialized sections which downloaded to the FLASH before to the internal zero wait-state RAM and run after the tool power up, this gives code execution a boost from up to 15 wait-states to zero wait-states.Completed the functional debugging of the program on the embedded system at last,the software was able to obtain raw logging data and upload the preprocessed result and working parameters both correct and in time. The debug result showed that the designed software turns out to meet the expectations. Besides, take advantages of the fast and conventional features of PSpice simulation, model and simulate the assumptions made in the debugging process on the key circuits of the tool, utilize the simulation results to guide the engineer to optimize the tool. The results indicates that the optimization, to some degree, improved the measurement range and accuracy of the tool.Finally, simulated the data preprocessing of main controller and communication circuit with MATLAB. After further processing, the results are presented in a more intuitionistic way, that result, to some degree, displays the measurement outcome of the formation resistivity with no correction at different frequency(different depth) of the tool.All the works finished in this article have laid a foundation for the development and engineering of the array laterolog logging tool.