The Quantity Traceability Method & Calibration Device Research Of Through Casing Resistivity Logging Tool

The calibration system of through-casing formation resistivity logging is mainly used for logging instrument commissioning,calibrating and adjusting.Specifically,the system not only detects the functions of logging instrument,calibrates resistivity curves and ensures the accuracy of the logging data,but also provides a test platform for debugging instrument and optimizes the system parameters.Therefore,this system is of vital importance in production,testing,calibration and maintenance of logging instrument.Firstly,the principle of through-casing formation resistivity logging is introduced in the paper,the relationship of the casing electrode potential and formation resistivity is analyzed,and the calculation formula of the apparent formation resistivity is derived.Secondly,the construction of the traditional calibration device is studied and the reasons why the traditional calibration device fails to achieve the result are summarized.In view of the problems,a new design scheme of the calibration system of through-casing formation resistivity logging is put forward according to measurement traceability of the single parameter and multi-parameter passing.The system is composed of seven parts: large current excitation source,backup arm source,main controller,serial port server,casing simulator,resistor array and calibration loop.The casing simulator replaces the actual casing,resistor array simulates the changes of formation resistivity,and the main controller realizes communication between the logging instrument and the computer.Finally,the PC system software is built in VB6.0,and four dynamic curves are built in the system software,namely,curve of voltage U₁ between two electrodes,curve of voltage U₂ between other two electrodes,excitation current I and reference voltage U,and the calibration equation is fitted.A new calibration and detection equipment of the through casing resistivity logging tool is designed and developed.The field test and calibration verification experiment of the equipment and the through casing resistivity logging tool are done.The results show that the measuring error of the through casing resistivity logging tool is less than 3.6% after the calibration,and the functions and measurement accuracy of the equipment are verified.The design requirements of functionally tested and calibration of the through casing resistivity logging tool are satisfied.