Method and system for introducing electric current into a well

A system for inhibiting formation of solids within a petroleum well comprising:

• a grounded wellhead of electrically conducting material,
• a casing of electrically conducting material attached to said wellhead,
• a tubing attached to said wellhead and positioned within said casing,
• collar means in said tubing and below said wellhead electrically insulating the tubing above said collar means from the tubing below said collar means,
• said tubing below said collar means formed of electrically conducting material,
• connecting means below said collar means electrically connecting said tubing and casing,
• vertically spaced insulators on said tubing insulating said tubing from said casing between said collar means and said connecting means, and
• a source of current connected to said wellhead and to said tubing immediately below said collar means.

A power transmission system for wells comprising:

• a grounded wellhead of electrically conducting material,
• a casing of electrically conducting material attached to said wellhead,
• a tubing attached to said wellhead and positioned within said casing,
• collar means in said tubing and below said wellhead electrically insulating the tubing above said collar means from the tubing below said collar means,
• said tubing above and below said collar means formed of electrically conducting materials,
• a load electrically connected to said tubing below said collar means,
• connecting means electrically connecting said load to said casing,
• vertically spaced insulators on said tubing insulating said tubing from said casing between said collar means and said load, and
• a source of current electrically connected to said wellhead and to said tubing below said collar means.

A tubing collar comprising:

• inner and outer tubular connectors of electrically conducting material concentrically arranged with one end of the inner connector positioned intermediate the ends of the outer connector and provided with threads for making up with the tubing above and below the collar,
• a plurality of circumferentially extending interlocking shelves carried by the inner and outer connectors,
• insulating material between the inner and outer connectors,
• said insulating material additionally extending from said one end of the inner connector along the inner surface through the outer connector and away from the inner connector a selected distance to minimize shorting between the tubular connectors by a mixture of conducting and non-conducting liquid flowing through the collar, and
• one of said connectors including means for connecting an electrical conduit to said one connector.

A system for inhibiting formation of solids within a petroleum well having a production tubing comprising,

• a coaxial cable extending down the tubing,
• said cable provided by a central conductor and a coaxial braid of steel wire along its entire length and wires of less resistance than said braid of steel wire in engagement therewith at spaced points along its axial length to provide a path of low resistance along a section of said cable,
• means connecting said central conductor and braid of steel wire at the lower end of the cable, and
• means for maintaining said cable extended in said tubing.

A system for heating the tubing of a petroleum well comprising a wellhead,

• a tubing suspended from the wellhead,
• a stuffing box on the wellhead,
• a multi-conductor cable supported by a saddleblock on the wellhead and extending down through the stuffing box and through said tubing to a selected depth in the well,
• means interconnecting said multi-conductor of said cable at said selected depths,
• and control means for a source of electric current at the surface connected to said conductors,
• at least one of said conductors having different resistances at different depths to provide uneven heating at different depths in the well;
• said cable including,
• a central conductor,
• inner insulation material around said central conductor,
• a braided steel conductor around said insulation material,
• outer insulation material around said braided steel conductor,
• and wire means having lower resistance than said braided steel conductor along the lower section of said cable and in electrical contact with said braided steel conductor to lower the total resistance of said lower cable section.