Tubing collar position sensing apparatus, and associated methods, for use with a snubbing unit

Snubbing apparatus for vertically moving a tubing string into and out of a well bore, the tubing string including a duality of elongated tubing joints interconnected end-to-end by an enlarged diameter tubing collar, said snubbing apparatus comprising:

• a vertically extending riser spool through which the tubing string may be axially moved into and out of the well bore;
• vertically spaced upper and lower blowout preventers mounted on said riser spool at opposite ends of a longitudinal section thereof, each of said upper and lower blowout preventers being individually closable to form a sliding pressure seal around a tubing joint portion of the tubing string, and individually openable to permit axial passage of the tubing collar therethrough;
• means for selectively moving the tubing string upwardly or downwardly through said riser spool;
• and
• means for detecting and indicating the entry of the tubing collar into said riser spool section, the vertical position of the tubing collar within said riser spool section, and the direction of vertical travel of the tubing collar through said riser spool section, said means for detecting and indicating including:
• electric induction coil means, operatively mounted on said riser spool section, past which the tubing collar may be moved as it traverses said riser spool section, and
• circuit means for supplying electrical power to said electric induction coil means at a predetermined frequency, detecting variations in the supplied electrical power attributable to variations in the vertical position of the tubing collar relative to said electric induction coil means, and responsively indicating the entry of the tubing collar into said riser spool section, the vertical position of the tubing collar within said riser spool section, and the direction of vertical travel of the tubing collar through said riser spool section.

Snubbing apparatus for vertically moving a tubing string into and out of a well bore, the tubing string including a duality of elongated tubing joints interconnected end-to-end by an enlarged diameter tubing collar, said snubbing apparatus comprising:

• a vertically extending riser spool through which the tubing string may be axially moved into and out of the well bore;
• vertically spaced upper and lower blowout preventers mounted on said riser spool at opposite ends of an essentially nonmagnetic longitudinal section thereof;
• means for selectively moving the tubing string upwardly or downwardly through said riser spool;
• and
• means for electromagnetically sensing the entry of the tubing collar into said riser spool section, said means for electromagnetically sensing including:
• an electric induction coil coaxially circumscribing said riser spool section,
• means for supplying electric power to said electric induction coil, and
• means for detecting an electric power phase shift occasioned by entry of the tubing collar into said riser spool section, and responsively generating an output signal indicative of said entry.

A method of detecting the entry of a tubing string joint connecting collar into a longitudinal section of a riser spool disposed between upper and lower blowout preventers during axial tubing string movement through the riser spool, said method comprising the steps of:

• securing an electric induction coil to the longitudinal riser spool section between the upper and lower blowout preventers;
• supplying electrical power to said electric induction coil;
• causing the tubing collar, as it enters said longitudinal riser spool section, to create a phase shift in said electrical power;
• and
• detecting said phase shift and responsively generating an output signal indicative thereof.

A method of detecting the entry of a tubing string joint connecting collar into a longitudinal section of a riser spool through which the tubing string is vertically moved, the vertical position of the collar within the riser spool section, and the direction of vertical travel of the collar through the riser spool section, said method comprising the steps of:

• securing upper and lower electric induction coils to the riser spool section;
• supplying electrical power to each of said upper and lower electric induction coils;
• causing the tubing collar, as it vertically traverses the riser spool section, to create phase shifts in the electrical power supplied to each of said upper and lower electrical induction coils;
• and
• detecting said phase shifts and responsively generating output signals combinatively indicative of the entry of the tubing collar into the riser spool section, the vertical position of the tubing collar within the riser spool section, and the direction of vertical travel of the tubing collar through the riser spool section.

Apparatus for sensing the entry, into a predetermined longitudinal section of a pipe extending downwardly into a well bore, of a tubing collar portion of an elongated tubing string being axially moved through the interior of said pipe, said apparatus comprising:

• electric induction coil means outwardly circumscribing said longitudinal section of said pipe;
• circuit means for supplying electrical power to said electric induction coil means at a predetermined frequency, detecting variations in the supplied electrical power attributable to variations in the longitudinal position of said collar portion relative to said longitudinal section of the pipe, and responsively generating output signal means indicative of the entry of said collar portion into said longitudinal section of the pipe;
• and
• isolating means for isolating the pipe interior above said section of pipe from the well bore pressure while permitting the axial passage of the tubing string through said section of pipe.