| Induction logging plays an important role in the resistivity logging field. With thedevelopment of logging technology, the array induction logging tool has become the maintool to measure the formation resistivity, due to the higher resolution, deeper depth ofinvestigation，clearer invasion indication and richer formation information. However, metalsinside or outside the array induction logging tool has some impacts on the measurementsignal. Taking the domestic array induction logging tool (MIT) as the study objection, theeffect characteirstic of the metal on MIT measurement have been studied by finite elementnumerical simulation sotfware (COMSOL). Research results have the important theoreticaland practical significance on the array induction logging tool design, manufacture and actualmeasurement. The study content includes the following three aspects.Firstly, the pirnciple of two-coil logging and the array induction logging with three coils,and COMSOL sotfware, and the theory of finite element calculation, and the basic structure ofthe array induction logging tool (MIT) are introduced. These are the theory basis for themodel.Secondly, metal impact inside MIT has studied. A two-dimensional axisymmetric modelis established with the COMSOL sotfware. Measurement signals are calculated in thesesituations, such as two ends metal, metal mandrel, shielding layer and multiple metals. Theresults show that impact of the shielding layer and the metal mandrel is more than the twoends metal which inlfuences the closer sub-arrays only. When a plurality of metal bodies exist,the inlfuence is greater than only the metal mandrel, less than only the shielding layer.Finally，metal impact outside MIT is investigated. The different positions and differentsizes of the metal are considered in the model. The results show that the mental impact outsideMIT on measurement-signal is obvious within a certain distance of the tool. The metal impacton the closest sub-array is bigger than other sub-arrays. |
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