Replaceable antennas for wellbore apparatus
An antenna structure is separately and independently formed with respect to a downhole tool. The antenna is adapted for easy and rapid deployment on the tool. An independently formed ‘partial ring section’ (or arcuate shaped member) contains an antenna coil. In one embodiment, two or more of the independently formed partial ring sections are placed in a recess on the tubular forming the downhole tool. In another embodiment, the partial ring sections can also be placed in one or more longitudinally distributed sections about the tool. Another embodiment includes partial ring sections forming an antenna with multiple coils of differing orientation to provide directional sensitivity.
1. An antenna for use in a downhole tool, comprising:
a first partial ring section disposed within a portion of a recess in and extending circumferentially around a tubular, the first partial ring section having two ends;
a first coil disposed on or in the first partial ring section, the first coil providing a current path that extends less than about 180 degrees about the tubular;
a second partial ring section disposed within a different portion of the recess and having two ends; and
a second coil disposed on or in the second partial ring section, the second coil providing a current path that extends less than about 180 degrees about the tubular;
wherein the ring sections are removeably secured to the tubular.
2. The antenna of claim 1 , further comprising a rubber layer disposed over the first and/or second partial ring sections.
3. The antenna of claim 1 , wherein each of the coils produces an axially directed dipole moment relative to a longitudinal axis of the tubular.
4. The antenna of claim 1 , wherein each of the coils produces a diagonally directed dipole moment relative to a longitudinal axis of the tubular.
5. The antenna of claim 1 , wherein each of the coils produces a transversely directed dipole moment relative to a longitudinal axis of the tubular.
6. The antenna of claim 1 , wherein the first coil produces an axially directed dipole moment relative to a longitudinal axis of the tubular and the second coil produces a diagonally directed dipole moment relative to the longitudinal axis of the tubular.
7. The antenna of claim 1 , wherein the first coil produces an axially directed dipole moment relative to a longitudinal axis of the tubular and the second coil produces a transversely directed dipole moment relative to the longitudinal axis of the tubular.
8. The antenna of claim 1 , wherein the first coil produces a diagonally directed dipole moment relative to a longitudinal axis of the tubular and the second coil produces a transversely directed dipole moment relative to the longitudinal axis of the tubular.
9. The antenna of claim 1 , further comprising a plurality of partial ring sections disposed within the recess, each partial ring section having a coil disposed thereon or therein, each coil providing a current path that extends less than about 180 degrees about the tubular.
10. The antenna of claim 9 , wherein:
at least one coil produces a diagonally directed dipole moment relative to a longitudinal axis of the tubular;
at least one coil produces a transversely directed dipole moment relative to the longitudinal axis of the tubular; and
at least one coil produces an axially directed dipole moment relative to the longitudinal axis of the tubular.
11. The antenna of claim 9 , wherein:
at least one coil produces a first transversely directed dipole moment relative to a longitudinal axis of the tubular;
at least one coil produces a second transversely directed dipole moment relative to the longitudinal axis of the tubular that is orthogonal to the first transversely directed dipole moment; and
at least one coil produces an axially directed dipole moment relative to the longitudinal axis of the tubular.
12. The antenna of claim 9 , wherein the partial ring sections are made from nonconductive materials.
13. The antenna of claim 12 , wherein each of the partial ring sections has a rubber layer disposed over the nonconductive materials.
14. The antenna of claim 1 , wherein the first partial ring section and the second partial ring section are made from nonconductive materials.
15. The antenna of claim 1 , further comprising a shield disposed over each partial ring section.
16. The antenna of claim 1 , wherein the tubular comprises one of a drill collar or a wireline tool.
17. The antenna of claim 1 , further comprising a plurality of coils disposed on or in at least one of the partial ring sections, wherein any one of the coils produces a dipole moment that is axial, transverse, or diagonal relative to a longitudinal axis of the tubular.
18. A method to repair or reconfigure an antenna disposed on a wellbore tool, comprising:
removing one or more partial ring sections disposed within a recess in and extending circumferentially around a tubular, each of the one or more partial ring sections having two ends and one or more coils disposed on or in the partial ring section, each of the one or more coils providing a current path that extends less than about 180 degrees about the tubular;
removeably securing one or more replacement partial ring sections within the recess, each of the one or more replacement partial ring sections having two ends and one or more coils disposed on or in the replacement partial ring section, each of the one or more coils providing a current path that extends less than about 180 degrees about the tubular; and
coupling an electrical source to one or more of the one or more coils disposed on or in the one or more replacement partial ring sections.
19. The method of claim 18 , wherein the coils are linked with electronic means adapted to energize the coils or receive electromagnetic signals from the coils.
20. The method of claim 18 , further comprising disposing a shield over the replacement partial ring sections.
21. The method of claim 18 , wherein the wellbore tool comprises one of a drill collar or a wireline tool.