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1. 发明申请

WO2022003366A1 METHOD OF AND APPARATUS FOR DETERMINING VARIATIONS IN WALL THICKNESS IN FERROMAGNETIC TUBES 审中-公开
公开(公告)号：WO2022003366A1
公开(公告)日：2022-01-06
申请号：PCT/GB2021/051684
申请日：2021-07-02
申请人： REEVES WIRELINE TECHNOLOGIES LIMITED
发明人： ASSOUS, Said , ELKINGTON, Peter Adrian Spencer , BACCIARELLI, Mark
IPC分类号： G01B7/06 , G01N27/83 , E21B47/085 , E21B47/006 , G01B7/10
摘要： A method of determining variations in wall thickness in an elongate, cylindrical, hollow, ferromagnetic tube, such as downhole borehole casing, defining a tube wall, comprises the steps of: a) energizing the tube with an at least longitudinally extending magnetic field generated inside the tube; b) using a magnetic field-detecting logging tool to generate two or more magnetic flux signals generated inside the tube externally of the material of the tube wall resulting from such energizing at plural circumferential locations on the inner surface of the tube and at a plurality of distances along the tube; c) iteratively, one or more times, using a model of the relationship between the two or more magnetic flux signals generated in Step b) and the thickness of the tube wall to derive the thickness profile of the tube wall by using (i) the magnetic permeability of the material of the tube deduced from the magnetic flux signals and (ii) a defect-free flux parameter representative of any non-linearity between the magnetic field strength and magnetic flux density in the tube, the iteration including: d) using the model to calculate an initial approximate wall thickness profile using an initial estimate of the defect-free flux parameter; e) calculating a metric that is representative of the magnitude of one or more physically inadmissible features in or forming part of the thickness profile; f) determining a quantitative norm of the metric of inadmissible features; g) varying the value of the defect-free flux parameter in order to minimize the quantitative norm of the metric of inadmissible features and selecting the defect- free flux parameter corresponding to minimizing of the quantitative norm; and h) generating one or more signals representing the thickness profile resulting from use of selected defect-free flux parameter as the thickness profile of the wall of the tube.

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