Increasing the resolution of electromagnetic tools for resistivity evaluations in near borehole zones

• US 7,427,862 B2
• Filed: 09/29/2006
• Issued: 09/23/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Dashevsky, Yuliy A., Borisov, Gleb A., Epov, Michail I.
• Primary Examiner(s): Patidar; Jay M
• Application Number:
  US11/537,105
• Publication Number:
  US 20080079431A1
• Time in Patent Office: 725 Days
• Field of Search: 324333-339, 702 6- 7
• US Class Current: 324/339
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

A tool for performing electromagnetic measurements within a borehole includes a transmitter including a coil having N-turns wound coaxially around a long metallic mandrel and a receiver including a coil having a one-turn receiving loop wound coaxially around the mandrel; wherein the transmitter is adapted for providing a current I of a predetermined frequency ƒ of a maximum intensity in a predetermined part of a near borehole zone; and wherein the receiver is disposed a distance L from the transmitter and adapted for receiving a signal from the transmitter. A method for use of the tool is provided.

Claims

1. A tool for performing electromagnetic measurements within a borehole, the tool comprising:

a transmitter comprising a coil having N-turns wound coaxially around a long metallic mandrel and a receiver comprising a coil having a one-turn receiving loop wound coaxially around the mandrel;

wherein the transmitter is adapted for providing a current I of a predetermined frequency ƒ

at a maximum intensity in near borehole zone; and

wherein the receiver is disposed a distance L from the transmitter and adapted for receiving a signal from the transmitter.

2. The tool as in claim 1, wherein the distance L is between about 0.4 meters and about 2.0 meters.

3. The tool as in claim 1, wherein the distance L is selected for providing the maximum intensity at a predetermined distance from a central axis of the tool.

4. The tool as in claim 1, wherein the frequency ƒ

is between about 0.001 MHz and about 10 MHz.

5. The tool as in claim 1, wherein the near borehole zone comprises a zone extending from a surface of the tool up to about one meter.

6. The tool as in claim 1, wherein a length of the long metallic mandrel comprises a length that does not substantially perturb performance of the transmitter and the receiver during operation of the tool.

7. A method for determining properties of formations in a near borehole zone, the method comprising:

applying a signal to a tool disposed into a borehole, the tool comprising a transmitter comprising a coil having N-turns wound coaxially around a long metallic mandrel and a receiver comprising a coil having a one-turn receiving loop wound coaxially around the mandrel;

wherein the transmitter is adapted for providing a current I of a predetermined frequency ƒ

at a maximum intensity in near borehole zone; and

wherein the receiver is disposed a distance L from the transmitter and adapted for receiving a signal from the transmitter;

generating the maximum intensity of the current I within the near borehole zone;

receiving the signal from the near borehole zone with the receiver; and

analyzing the signal to determine the properties of the formations.

8. The method as in claim 7, wherein analyzing provide for determination of at least one of filtration capacity for a local reservoir, permeability, capillary pressure, and relative permeability of the surrounding formations.

9. The method as in claim 7, wherein the generating comprises generating the maximum intensity in a predetermined part of the near borehole zone.

10. The method as in claim 7, further comprising generating the maximum intensity at a plurality of predetermined locations to provide for determination of the properties at each of the locations.

11. A computer program product stored on machine readable media and comprising instructions for determining properties of formations in a near borehole zone, by:

applying a signal to a tool disposed into a borehole, the tool comprising a transmitter comprising a coil having N-turns wound coaxially around a long metallic mandrel and a receiver comprising a coil having a one-turn receiving loop wound coaxially around the mandrel;

wherein the transmitter is adapted for providing a current I of a predetermined frequency ƒ

at a maximum intensity in near borehole zone; and

wherein the receiver is disposed a distance L from the transmitter and adapted for receiving a signal from the transmitter;

generating the maximum intensity of the current I within the near borehole zone;

receiving the signal from the near borehole zone with the receiver; and

analyzing the signal to determine the properties of the formations.

12. The method as in claim 11, wherein analyzing provide for determination of at least one of filtration capacity for a local reservoir, permeability, capillary pressure, and relative permeability of the surrounding formations.

13. The method as in claim 11, wherein the generating comprises generating the maximum intensity in a predetermined part of the near borehole zone.

14. The method as in claim 11, further comprising generating the maximum intensity at a plurality of predetermined locations to provide for determination of the properties at each of the locations.