Research On The Application Of Through Casing Resistivity Logging

The domestic through casing resistivity logging instruments are mostly imported fromabroad. Besides the higher price, the maintenance and alteration of instruments and themanagement of accessories are controlled by human. It is imperative to have our owntechnology in today that science and technology is productivity.Firstly, the basic principle of through casing resistivity logging is introduced andanalysed in the thesis. Based on the understanding of each part of the structure, themathematical model of the through casing resistivity logging system is established combiningwith the design experience of logging instrument which is more mature, and the measurementformula of resistivity in the steel casing is calculated by the node voltage method.Secondly, aiming at the complex principle of through casing resistivity logging, and baseon the analysis of the model of through casing resistivity logging system, the design proposalof system is proposed. Each weak signal of voltage acquired by this logging system, as wellseach collected voltage and current are calculated in the measurement formula of resistivitylogging system through the steel casing wells. The experimental results show that this methodhas a high accuracy of measuring data and reaches the detection requirements of the weaksignal of resistivity. After the characteristic analysis of transmission mode of CAN bus, CANbus transmission mode is applied in the system, and the speed of data transmission isimproved. With the technology of over-sampling, noise-shaping and digital filtering,∑-△ADC can efficiently reduce the quantization noise from output signal band, thus improve theSNR (signal to noise ratio). The modulation process and demodulation process of∑-△issimulated by MATLAB.Compared with traditional Nyquist converters,∑-△ADC reducethe requirements of performance specification and device accuracy to analog circuits, simplifythe design. Lastly，the design and debug of circuit are completed combining the actual system, andthe experimental results show that this system has a certain practicality and promotional valuein the measuring technology of formation resistivity in the steel casing wells.