Power tong positioner

A method for positioning a power tong unit longitudinally along a tubular, with respect to the position of a threaded connection seam or end, comprising the steps of:

• a) providing a power tong unit comprising an electric coil mounted thereon;
• a source of electric current connected to said electric coil;
• a means for detecting a change in said electro-magnetic field of said electric coil, said means for detecting comprising a digital processor, in response to relative movement between said electric coil and said tubular in a direction substantially parallel to the longitude of said tubular, and wherein said change in said electro-magnetic field comprises a chance in at least one of impedance, current, and phase angle of said electric current;
• b) providing a portfolio of surface profile attributes corresponding to electric coil impedance measurements on a plurality of tubulars and tubular connections, said portfolio stored in a database, said portfolio including impedance measurements on one or more of tool joint upset shapes, identification grooves, hardbanding, and connection seams;
• c) selecting, from said portfolio, a surface profile corresponding to the tubular and tubular connection relative to which said power tong unit is to be positioned;
• d) positioning said electric coil, through which an alternating electric current is being flowed, sufficiently close to a tubular that said tubular is within an electro-magnetic field emanating from said coil;
• e) creating relative movement between said electric coil and said tubular along the longitude of said tubular, while said electric coil remains at a substantially constant distance from an outer surface of said tubular, until a threaded connection seam or end is within said electro-magnetic field;
• f) detecting a change in said electro-magnetic field, caused by the presence of said threaded connection end or other defined attribute therein, wherein said change in said electro-magnetic field comprises a change in at least one of impedance, current, and phase angle of said alternating electric current, and wherein said change is detected by a digital processor, and wherein said change is caused by one or more surface profile attributes;
• g) by comparison with said surface attribute profile, determining which of said changes is caused by said connection end or other defined attribute therein, as opposed to other attributes;
• h) generating a signal when said change is detected, and sending said signal to a processor, said signal comprising data from which a position of said connection end may be determined;
• and
• I) emitting a signal from said processor to a power positioner holding a power tong unit, said power positioner positioning said power tong unit along a longitude of said tubular such that said threaded connection may be gripped by said power tong unit, for makeup or breakout of said threaded connection.