INDUCTION SONDE TO DETERMINE DEFECTS IN CASING STRING Russian patent published in 2003 - IPC

FIELD: well logging, aids monitoring technical state of casing and tubing strings. SUBSTANCE: induction sonde incorporates non-magnetic sealed case 1 with cylindrical base 2 that carries magnetic circuit 3 with pole faces 4 and generator coil 5 which turns are arranged coaxially to cylindrical base 2, induction coils 6 positioned axially and equidistantly with reference to cylindrical base 2. Axes of induction coils 6 in each pair are displaced one relative to another and coils are connected in pairs and in opposition. Magnetic circuit 3 comes in the form of hollow cylinder with solid pole faces 4, thickness of cylinder wall and height of each face are equal and their values are found by mathematical formula. Distance between faces 4 of magnetic circuit 3 is established by mathematical expression. Induction coils 6 are multiturn frames without cores, they have form of parallelogram in section with inclination angle of its larger side to cylindrical base 2 calculated by mathematical formula. Even number of induction coils 6 are is uniformly positioned in two rows between faces 4 of magnetic circuit 3 along circumference. Alignment between coils should be followed. Each pair of induction coils 6 is presented by diametrically opposite coils from different rows. EFFECT: enhanced sensitivity and simplified design of induction sonde. 5 dwg