Profilograph for examining pipes in oil wells

Claim 1

Apparatus for the continuous and remote recording of sizes and shapes of cross-sections of columns of casing pipes extending into wells below ground comprising; a source of alternating current located on the surface of the ground; an exploration unit fastened to a logging cable, said exploration unit being lowered and raised within said column of casing pipes by said cable; a measurement unit including an electric circuit mounted on the ground surface and being connected to said exploration unit by said logging cable and having current supplied thereto from said alternating current source; a recorder for cross-sectional profile diagrams having an input connected to the output of said measurement unit and including a synchronous motor connected to said alternating current source for effecting movement of the diagram of said recorder; a recorder for a spiral profile having an input connected to the output of said measurement unit and including means for moving the diagram synchronously with the movement of said exploration unit; said exploration unit comprising a non-magnetic casing, a reference-voltage transformer, a rotary transformer pickup, a current collector in the form of slip rings, a synchronous motor including speed reduction means by means of which said transformer pickup is rotated about the longitudinal axis of this exploration unit; said pickup having a primary and a secondary winding formed about a U-shaped core with pole terminals separated from each other and facing the wall of said column of casing pipes; said referencevoltage transformer having a U-shaped core including a primary and a secondary winding, said transformer including an adjustable armature adjacent the poles of the core enabling adjustment of the diamagnetic clearance between said core and the armature; the primary windings of said pickup and of said reference-voltage transformer being wound with a high-resistance wire and connected in series and via said slip rings to the conductors of said logging cable, and the measurement unit to said a.c. source; the secondary windings of said pickup and reference-voltage transformer having opposing connection and being connected to said measurement unit via said slip rings and the phantom circuit of the cable; said measurement unit comprising a matching transformer with a primary winding connected via the phantom circuit of the cable to said secondary windings of the pickup and reference-voltage transformer, and a rectifying bridge being connected to the secondary winding of said matching transformer and delivering signals to said recorders.