Research On Magnetic Flux Leakage Detection Technology For Electromagnetic Combined Tubing Defects

Tubing is an indispensable and commonly used material for oil,gas,and water well production and operates in a well with a corrosive medium.Under the effect of piston effect,bulging effect,temperature effect and spiral bending,the tubing string is subjected to complex loads,resulting in failure of the tubing,and problems such as disconnection,detachment,leakage,and jamming of the tubing.The main failure mode of the oil pipe is divided into a horizontal defect and a longitudinal defect according to the defect extension direction.The closer the angle of the defect cutting magnetic lines is to the orthogonality,the greater the leakage magnetic field strength is,and the best effect of defect detection is.Therefore,in order to make a full inspection of the flaws in the tubing,it is necessary to perform the magnetization in both the lateral(horizontal)and longitudinal(axial)directions.In this paper,the engineering ? 73 oil pipe is taken as the test object,and an electromagnetic and permanent magnet-type oil pipe defect magnetization detection.Firstly,the magnetic flux leakage detection technology in non-destructive testing is selected as the inspection method for oil pipe defects.Based on the fundamental theorem of electromagnetic field and Maxwell's equations,the finite element model under the analytical method and the finite element model under the numerical method are established.And the choice of magnetization technology and measurement components was studied.Secondly,the longitudinal magnetization of the tubing is performed by means of DC coil magnetization.The parameters of the coil are designed and selected through theoretical calculation of the coil magnetization.The magnetization of the tubing is transverse magnetized using a permanent magnet magnetization method,and the permanent magnet magnetization is preliminarily determined through the magnetic circuit design.The material and structure dimensions of the device.The finite element analysis of the magnetization process was performed using Anosoft software.The tubing satisfies the magnetization requirements of the defect detection,verifying the correctness of the theoretical calculation of the defect magnetization device.Thirdly,the simulation of the magnetic flux leakage detection of the horizontal and vertical flaws in the tubing was carried out.Including the probe lift-off value and defect geometry impact on the defect signal.Aiming at tubing detection as dynamic detection process,Ansoft was used to carry out dynamic simulation analysis of transverse defects and longitudinal imperfections of the tubing,and the linear velocity and speed of tubing defects detection were selected based on the simulation results.Finally,the horizontal and vertical flaw detection experiments of the oil pipe were carried out,and the experimental scheme was formulated,including the part of the defect magnetization device,the part of the defect detection probe,and the design of the defect signal acquisition and storage part.The artificial flaws of different defect sizes were machined using the method of digital milling.Defects were tested.The experimental results and the simulation results are basically the same,which verifies the correctness of the simulation analysis and the feasibility of the magnetization detection device.