Study Of High Resolution Induction And Digital Spherical Focus Logging System

Considering the demand of exploration and extraction of thin oil reservoir in domestic oilfields，this research studied induction logging and digital spherical focus logging(SFL) systembased on fundamental theory of electric logging and Hihg Resolution Induction Logging Tool.Main research contents included study of theories and analysis of detecting performance,circuits of down whole system and experiment.Based on the dual coil structure in the induction logging theory, the high resolution5coilstructure was raised, which increased the radial detecting depth and vertical resolution of thisinstrument. Digital focus method was adopted to achieve conventional spherical focuslogging，by which the size of instrument could be reduced and the stability and serviceabilitycould be improved. In terms of mechanical structure, this paper used a pattern which puts theinduction coil and focus electrode array in two coaxial mandrils. In order to control theworking states of the logging tool and process the data, we used FPGA and DSP as the coreparts of system. Data acquisition of downwhole logging signal is also important in thissystem，so16bit high-precision A/D converter is used. Simulation and debug of circuitmodules and experiment of imitating layer for SFL were completed in this article.The applications of FPGA, DSP and ADC not only were the way to achieve the digitalfocus for SFL, but also improve the performance of this tool. This research indicated thatlogging instrument is developing to integration, digitization and high-resolution. Meanwhile,it is helpful to facilitate the development of logging technology in our country.