Research On Corrosion Detecting Methods And Technologies For Metal Casing

Metal casing has a large number of applications in the oil industry, and casing corrosionhas become a kind of inevitable phenomenon due to the long-term impact of various factorssuch as changes in formation stress and temperature, corrosive liquid/gas. Casing damage wellhas become a thorny problem in oilfield exploitation, which not only affects the service life ofoil and water well, oil and gas production and water injection effect, but also can lead tovarious oil well quality accidents and huge economic losses. Monitoring the quality of casingcorrosion situation in a timely manner can effectively avoid all kinds of oil well productionaccident and reduce property losses. Casing corrosion detection technology, therefore, hasgreat application space and practical value in oil ifeld production.Field distribution scanning method was applied to detect casing corrosion in this research.Firstly, the principle of ifeld distirbution scanning method to detect the casing corrosion andtesting steps were analyzed，and stable current ifeld theory and finite element method (FEM)were introduced in the paper. By using the COMSOL finite element analysis software, casingmodel, such as uniform corrosion, perforation, crack defects etc, was built and computed.Secondly，the simulation was accomplished in the DC exciting models, and the structureparameters of the electrode system were given based on a large number of simulationexperiments. Under the DC exciting model in the current ifeld, anomaly changes in currentdensity and potential distribution in defective casing wall were analyzed, then a qualitativeevaluation of casing corrosion was made. Fanally, in the electric and magnetic ifeld，models ofuniform corrosion and blind hole corrosion were simulated and calculated，and the problem ofdistinguishing corrosion of internal wall from that of external wall was elaborated based on theprinciple of skin effect. Meanwhile, by taking the mixed corrosion model as an example,measurement results was interpreted as a2D image in MATLAB through applyingtechnologies of multi-frequency excitation, array measurement and array signal synthesisprocessing, then the type and location of corrosion can be more directly and accuratelypresented. The paper also designed the electrode arrangement, distirbution structure and theoverall scheme of signal acquisition system in combination with the simulation experimentresults.This thesis proposes a kind of casing corrosion detection method based on field distribution scanning method, which provides a new method for existing casing corrosiondetection technology, and the simulation results have great guiding significance in engineeringapplications.