Claims
- 1. Apparatus for nuclear magnetic resonance logging that is mountable in a drill string for logging of formations surrounding a borehole, comprising:a tubular drill collar having a generally cylindrical inner surface having an inner diameter and a generally cylindrical outer surface having an outer diameter; first means in said drill collar for producing a first magnetic field; second means in said drill collar for producing a second magnetic field; and means in said drill collar for receiving nuclear magnetic resonance signals from an investigation region in the formations; said second means comprising an antenna disposed in a recess spanning an axial extent in said outer cylindrical surface, the outer surface of said drill collar having a diameter that is reduced from said outer diameter over the axial extent of said recess, and the inner surface of said drill collar having a diameter that is not substantially reduced from said inner diameter over the axial extent of said recess.
- 2. Apparatus as defined by claim 1, wherein said receiving means includes means coupled with said antenna for detecting signals induced in said antenna.
- 3. Apparatus as defined by claim 2, wherein said recess is an annular recess.
- 4. Apparatus as defined by claim 3, wherein said antenna comprises at least one generally cylindrical arc-shaped conductor plate in said recess.
- 5. Apparatus as defined by claim 3, wherein said antenna comprises a plurality of generally cylindrical arc-shaped conductor plates in said recess.
- 6. Apparatus as defined by claim 3, wherein said antenna comprises at least one multi-turn loop formed in a generally cylindrical arc shape in said recess.
- 7. Apparatus as defined by claim 2, wherein said antenna comprises at least one generally cylindrical arc-shaped conductor plate in said recess.
- 8. Apparatus as defined by claim 2, wherein said antenna comprises a plurality of generally cylindrical arc-shaped conductor plates in said recess.
- 9. Apparatus as defined by claim 2, wherein said antenna comprises at least one multi-turn loop formed in a generally cylindrical arc shape in said recess.
- 10. Apparatus as defined by claim 9, wherein said at least one multi-turn loop comprises a plurality of multi-turn loops.
- 11. Apparatus as defined by claim 9, wherein said loop has an axis that is substantially perpendicular to the longitudinal axis of said drill collar.
- 12. Apparatus as defined by claim 9, wherein said generally cylindrical arc shape of said loop is centered on a line oriented in the direction of the longitudinal axis of said drill collar.
Parent Case Info
This is a division of U.S. patent application Ser. No. 09/094,201, filed Jun. 9, 1998 which is a continuation-in-part of U.S. patent application Ser. No. 08/880,343, filed Jun. 23, 1997, now U.S. Pat. No. 5,977,768, issue date Nov. 2, 1999.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5629623 |
Sezginer et al. |
May 1997 |
A |
5923167 |
Chang et al. |
Jul 1999 |
A |
6184681 |
Heisler et al. |
Feb 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
2 310 500 |
Aug 1997 |
GB |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
08/880343 |
Jun 1997 |
US |
Child |
09/094201 |
|
US |