METHOD OF ANALYSING WELL CASING INNER SURFACE Russian patent published in 2010 - IPC E21B47/00 E21B49/00 

FIELD: oil-and-gas production.

SUBSTANCE: main transducer output voltages are measured in every profilographed point on analysed profile, auxiliary transducer output voltages are subtracted therefrom and differential voltages are then recorded and processed. Note here that auxiliary transducer voltages are taken to be proportional to solution magnetic conductivity by shunting transducer pole tips with the help of ferromagnetic body so that there is a clearance between the latter and casing outer surface to allow free circulation of said solution. Ferromagnetic body is located at a distance from casing outer surface that does not exceed transducers operating ranges, while auxiliary transducer proper is arranged at one height with the main transducer. In analysis, transducer calibration curve is corrected with due allowance for solution magnetic conductivity variations. For this, short-term shunting of the main transducer pole tips is performed to produce reference differential voltage that corresponds to zero clearance between well casing inner surface and transducer case outer surface. Controlled clearances corresponding to each profilographed point of j-th profile are defined using mathematical relationship cited in this invention.

EFFECT: higher accuracy of determination well casing inner surface wear.

8 cl, 8 dwg