Apparatus and methods for making azimuthal resistivity measurements
A resistivity measuring tool used in a drillstring having a drill bit on a distal end for drilling a wellbore in a formation includes a tool body having a longitudinal axis, a transmitting antenna, and a receiving antenna. The receiving antenna includes an antenna body having a longer axis disposed longitudinally in the tool body, and a wire coil having a central axis disposed around the antenna body, wherein the wire coil central axis is substantially perpendicular to the longer axis of the antenna body, and wherein the wire coil is configured to generate a magnetic moment orthogonal to the tool body longitudinal axis. The transmitting antenna is configured to transmit electromagnetic energy into the formation and induce a voltage signal related to a parameter of the formation in the receiving antenna.
1. A tool comprising:
a tool body;
a receiving antenna configured to be disposed within a pocket of a tool body wherein the receiving antenna comprises:
an antenna body having a longer axis configured to be disposed longitudinally in the tool body; and
a wire coil configured to generate a magnetic moment wherein the wire coil has a central axis disposed around the antenna body and wherein the wire coil central axis is angled with respect to the longer axis of the antenna body,
wherein the receiving antenna is configured to receive a voltage signal related to a parameter of a geologic formation;
wherein the tool further comprises an antenna shield configured to be placed over the pocket of the tool body;
and wherein the tool body has an outer perimeter and wherein the pocket is formed within only a portion of the outer perimeter.
2. The tool of claim 1 , wherein the receiving antenna is disposed within a pocket extending radially inward from an outer surface of the tool body.
3. The tool of claim 2 , further comprising a non-conducting material disposed within the pocket beneath and around the wire winding.
4. The tool of claim 2 , further comprising a magnetic material disposed within the pocket beneath and around the wire winding.
5. The tool of claim 2 , wherein the pocket extends radially inward from the outer surface a maximum radial depth of approximately one inch.
6. The tool of claim 2 , wherein the pocket extends axially a maximum of approximately ten inches along the longitudinal axis.
7. The tool of claim 2 , further comprising an antenna shield having openings therein covering the antenna body and wire winding within the pocket and attached to the tool body.
8. The tool of claim 7 , wherein the openings in the antenna shield are curved.
9. The tool of claim 1 , further comprising multiple receiving antennas proximate to the outer surface of the tool body and azimuthally-spaced around a circumference of the tool body.
10. The tool of claim 9 , wherein the multiple receiving antennas are azimuthally-spaced at or less than 180 degrees apart.
11. The tool of claim 9 , wherein the multiple receiving antennas are connected in series or parallel.
12. The tool of claim 1 , further comprising a transmitting antenna.
13. The tool of claim 12 , wherein the transmitting antenna comprises a wire winding that is symmetric about the longitudinal axis of the tool body.
14. The tool of claim 1 , further comprising a sensor configured to measure the angular position of the tool body relative to the wellbore.
15. The tool of claim 1 , further comprising a transmitting antenna configured to induce the voltage signal related to a parameter of the geologic formation that is received by the receiving antenna.
16. The tool of claim 1 , wherein the antenna body comprises wire grooves configured to hold the wire in place.
17. The tool of claim 1 , wherein the antenna shield comprises one or more openings.
18. The tool of claim 1 , wherein the antenna shield is configured to be attached to the tool body with bolts.