INDUCTION LOGGING TOOL TO IDENTIFY DEFECTS OF CASING AND TUBING JOINTS Russian patent published in 2008 - IPC E21B49/00 G01N27/83 

FIELD: petroleum industry.

SUBSTANCE: invention is referred to oilfield geophysics, i.e. to technical condition controls of casing and tubing downhole. For this purpose, the logging tool consists of nonmagnetic sealed housing and cylindrical (C) bed (B) with coaxially mounted hollow C magnetic conductor with end pole terminals (EP) and EP claw mounted at the three height distance from the lower EP terminal. Inductance coils are mounted coaxially to the empty C magnetic conductor on both sides of the EP claw. Inductance coil mounted above the EP claw makes exciter coil, inductance coil mounted below the EP claw making the power coil. The said coils are engaged oppositely. Additional bucking coil is mounted coaxially to the power coil. Induction logging tool contains even number of indicator coil represented by multiloop frames without core parallelogram in cross section with a slope of larger part to the cylindrical bed. Indicator coils are installed axially and equidistantly from the cylindrical bed and mounted even circumferentially in two rows with alignment between the last ones and immediately adjacent between them selves. Indicator coils of the top raw are installed immediately adjacent with smaller parallelogram part to the top EP terminal. Indicator coils of the bottom row are mounted above the EP claw immediately adjacent with indicator coils of the top raw. Windings of indicator coils are connected in couples. The pair is represented by adjacent indicator coils of different rows engaged oppositely. Windings of the indicator coils are made single-wired. Width of the indicator coil winding is calculated from the expression. Slope angle of the larger parallelogram side to the CB is calculated from the expression. Measuring coils are identical to indicator coils and located inside them, connected between each other and with terminal of the bucking coil.

EFFECT: higher response and resolution capability of the induction logging tool.

6 dwg