| Oil casing is a metal pipeline supporting the shaft lining of oil wells.It plays an important role in oil exploitation and exploration.However,due to the influence of service life and operating environment,casing is prone to wear and tear.Oil leakage caused by pipeline damage will directly affect oil field productivity,resulting in huge economic losses and ecological environment problems.Therefore,it is of great practical significance to study the detection and evaluation of pipeline wear and tear.Multi-frequency eddy current testing technology is a new non-destructive testing technology.It has the advantages of high detection sensitivity and little influence by environmental factors.The thesis based on the eddy current detection theory and combined with the detection scheme of the original magnetic thickness gauge,the simulation study and parameter optimization design of the detection sensor are carried out.The influence of environmental factors on the underground measurement is analyzed by finite element simulation,and the detection method is further improved to improve the accuracy of the physical property detection of ferromagnetic pipelines.Firstly,the thesis introduces the advantages of eddy current effect in detecting oil casing.Then,based on the principle of eddy current detection,a mathematical model for measuring the physical properties of pipeline through transmission impedance between transceiver and receiver coils is established and deduced.The influencing factors of transmission impedance increment are analyzed and a multi-frequency eddy current detection scheme is proposed.Secondly,two-dimensional and three-dimensional simulation models and inversion databases of pipeline physical property detection are established by means of finite element software,and the rationality of simulation models is analyzed based on eddy current effect.Then,through the finite element simulation method,the influence of different sensor coil groups and instrument support mandrel on the detection effect is analyzed.Titanium alloy is selected as the mandrel material of magnetic thickness gauge,and a new sensor is designed and tested.Then,on the basis of using multi-frequency eddy current to detect the physical properties of pipelines,the influence of environmental factors such as the deviation of the device from the axis of pipelines,the infiltration of oilfield water into pipelines and the high temperature environment on the detection results is analyzed through simulation,andthe corresponding detection and correction schemes are studied.Finally,signal detection platform and pipeline physical attribute inversion algorithm are introduced.According to the inversion effect of pipeline inner diameter and magnetic permeability when the instrument has weak eccentricity,a dual-coil switching detection scheme is formulated.Through the measurement of ferromagnetic pipelines with different inner diameters,the rationality of the design optimization of multi-frequency eddy current detection scheme for magnetic thickness gauge is verified.The test results show that the instrument has a high detection accuracy for the inner diameters of pipelines,and the device meets the design requirements. |
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