Method and Tool for Directional Electromagnetic Well Logging

• US 20140292341A1
• Filed: 10/23/2013
• Published: 10/02/2014
• Est. Priority Date: 04/01/2013
• Status: Active Grant

• Current Assignee: Oliden Technology LLC
• Original Assignee: Oliden Technology LLC
• Inventors: Yang, Jian
• Granted Patent: US 9,389,332 B2
• Time in Patent Office: Days
• US Class Current: 324/339
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

A directional antenna, system and method are provided. The methods include acquiring a plurality of data pairs, each data pair comprising an induced signal at a receiver and a corresponding toolface angle using a tool including at least one antenna assembly, as described herein. It further discloses a method to generate a measurement containing information about the directionality of the formation by calculating areas of an induced signal function approximated by the plurality of data pairs.

Claims

1. A method, comprising:

disposing a tool in a borehole disposed in a formation comprising;

at least one transmitter and at least one receiver;

wherein at least one of the transmitter and the receiver is a directional antenna; and

wherein the transmitter and receiver are axially spaced relative to one another;

acquiring in the borehole a plurality of data pairs, each data pair comprising a induced signal at the at least one receiver and a corresponding toolface angle from among a total toolface range; and

calculating at least one area of an induced signal function approximated by the plurality of data pairs to generate a measurement characterizing the formation.

2. The method according to claim 1, further comprising:

dividing the total toolface range into a plurality of sub-sets;

calculating, for each sub-set of the total toolface range, the area of the induced signal function to generate the measurement characterizing the formation.

3. The method according to claim 1, wherein the plurality of sub-sets is four sub-sets.

4. The method according to claim 1, wherein the plurality of sub-sets is eight sub-sets.

5. The method according to claim 1, wherein the plurality of sub-sets span equal ranges of toolface angles.

6. The method according to claim 1, wherein the measurement comprises one or more of:

a 0^th harmonic coefficient of the induced signal,

one or more 1^st harmonic coefficients of the induced signal, and

one or more 2^nd harmonic coefficients of the induced signal.

7. The method according to claim 1, wherein the calculating comprises a discrete integration method.

8. The method according to claim 7, wherein the discrete integration method comprises a trapezoidal integration method.

9. The method according to claim 1, wherein the measurement further comprises a linear combination of one or more of the 0^th harmonic coefficient, the 1^st harmonic coefficient, and the 2^nd harmonic coefficient.

10. The method according to claim 1, wherein the measurement further comprises a magnitude ratio or a phase difference between two different linear combinations of one or more of the 0^th harmonic coefficient, the 1^st harmonic coefficient, and the 2^nd harmonic coefficient.

11. The method according to claim 1, wherein the measurement further comprises a linear combination of the areas of the plurality of sub-sets of the induced signal function.

12. The method according to claim 1, wherein the measurement further comprises a magnitude ratio or a phase difference between two different linear combinations of the areas of the plurality of sub-sets of the induced signal function.

13. The method according to claim 1, further comprising using the measurement characterizing the formation.

14. The method according to claim 1, wherein the at least one directional transmitter comprises:

a tool body section with a longitudinal axis, the tool body section having an external surface comprising;

a plurality of grooves of reduced radial dimension spaced around the tool body section, each of the plurality of grooves being oriented at a non-axial direction with respect to the longitudinal axis of the tool body section;

a plurality of lands spaced around the tool body section, each land of the plurality of lands separating at least two adjacent grooves of the plurality of grooves;

an antenna pathway traversing the plurality of grooves and plurality of lands around the tool body section; and

a coil disposed in the antenna pathway.

15. The method according to claim 1, wherein the at least one axially spaced directional receiver comprises:

a tool body section with a longitudinal axis, the tool body section having an external surface comprising;

a plurality of grooves of reduced radial dimension spaced around the tool body section, each of the plurality of grooves being oriented at a non-axial direction with respect to the longitudinal axis of the tool body section;

a plurality of lands spaced around the tool body section, each land of the plurality of lands separating at least two adjacent grooves of the plurality of grooves;

an antenna pathway traversing the plurality of grooves and plurality of lands around the tool body section; and

a coil disposed in the antenna pathway.

16. A downhole measurement tool, comprising:

at least one transmitter;

at least one receiver;

wherein at least one of the transmitting antenna and the receiving antenna comprises a directional antenna; and

a controller configured to (i) cause the tool to acquire a plurality of data pairs while rotating in a subterranean borehole, each data pair comprising an induced signal and a corresponding toolface angle from among a total toolface range; and

(ii) calculate downhole at least one area of an induced signal function approximated by the plurality of data pairs to generate a measurement characterizing the formation.

17. The downhole measurement tool of claim 16, wherein the controller is further configured to divide the total toolface range into a plurality of sub-sets;

and calculate, for each sub-set of the total toolface range, the area of the induced signal function to generate a measurement characterizing the formation.

18. The downhole measurement tool of claim 17, wherein the plurality of sub-sets is four sub-sets.

19. The downhole measurement tool of claim 17, wherein the plurality of sub-sets is eight sub-sets.

20. The downhole measurement tool of claim 17, wherein the plurality of sub-sets span equal ranges of toolface angles.

21. The downhole measurement tool of claim 16, the controller being further configured to output the measurement comprising one or more of:

a 0^th harmonic coefficient of the induced signal, one or more 1^st harmonic coefficients of the induced signal, and one or more 2^nd harmonic coefficients of the induced signal.

22. The downhole measurement tool of claim 16, the controller being further configured to apply a discrete integration method.

23. The downhole measurement tool of claim 16, the controller being further configured to output the measurement comprising a linear combination of one or more of the 0^th harmonic coefficient, the 1^st harmonic coefficient and the 2^nd harmonic coefficient.

24. The downhole measurement tool of claim 16, the controller being further configured to output the measurement comprising a magnitude ratio or a phase difference between two different linear combinations of one or more of the 0^th harmonic coefficient, the 1^st harmonic coefficient, and the 2^nd harmonic coefficient.

25. The downhole measurement tool of claim 16, the controller being further configured to output the measurement comprising a linear combination of the areas of the plurality of sub-sets of the induced signal function.

26. The downhole measurement tool of claim 16, the controller being further configured to output the measurement comprising a magnitude ratio or a phase difference between two different linear combinations of the areas of the plurality of sub-sets of the induced signal function.

27. The downhole measurement tool of claim 16, the controller being further configured to transfer to the surface the measurement characterizing the formation.

28. The downhole measurement tool of claim 16, wherein the transmitter and the receiver are deployed on a single tool module.

29. The downhole measurement tool of claim 16, wherein the transmitter and the receiver are deployed on more than one separable tool modules.