Method For Improving Wellbore Survey Accuracy And Placement

• US 20130002257A1
• Filed: 06/20/2012
• Published: 01/03/2013
• Est. Priority Date: 06/29/2011
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: McElhinney, Graham A., Ceh, Leon, Stenerson, Kenneth, Forbes, Euan
• Granted Patent: US 9,297,249 B2
• Time in Patent Office: Days
• US Class Current: 324/346
• CPC Class Codes: E21B 47/022 of the borehole, e.g. using geomagnetism
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: G01V 3/40 specially adapted for measuring magnetic field characteristics of the earth

Abstract

Methods for improving wellbore survey accuracy and placement are disclosed. The Earth'"'"'s magnetic field may be measured at a magnetically clean surface location and correlated with a non-magnetic reference direction to obtain a direction of the Earth'"'"'s field (e.g., a magnetic declination or a magnetic inclination). The direction of the Earth'"'"'s magnetic field may in turn be processed in combination with magnetic measurements made in a subterranean borehole to obtain one or more survey parameters.

Claims

1. A surveying method comprising:

(a) obtaining a non-magnetic reference direction at a magnetically clean surface location;

(b) measuring a magnetic field of the Earth at the magnetically clean surface location; and

(c) processing the reference direction obtained in (a) and the magnetic field of the Earth measured in (b) to determine a direction of the Earth'"'"'s magnetic field.

2. The surveying method of claim 1, wherein the direction of the Earth'"'"'s magnetic field comprises at least one of a magnetic declination and a magnetic inclination of the Earth'"'"'s magnetic field.

3. The surveying method of claim 1, further comprising:

(d) measuring a magnetic field in a subterranean borehole; and

(e) processing the magnetic field measured in (d) with the direction of the Earth'"'"'s magnetic field determined in (c) to obtain a magnetic azimuth of the subterranean borehole with respect to true north.

4. The surveying method of claim 1, further comprising:

(d) measuring a magnetic field in a subterranean borehole; and

(e) processing the magnetic field measured in (d) with the direction of the Earth'"'"'s magnetic field determined in (c) to obtain an interference magnetic field emanating from another subterranean borehole.

5. A surveying method comprising:

(a) obtaining a first global positioning measurement at a first surface location;

(b) obtaining a second global positioning measurement at a second surface location;

(c) processing the first and second global positioning measurements obtained in (a) and (b) to determine a reference direction between the first and second surface locations;

(d) measuring a magnetic field of the Earth at the first surface location; and

(e) processing the reference direction obtained in (c) and the magnetic field of the Earth measured in (d) to determine at least one of a magnetic declination and a magnetic inclination of the Earth'"'"'s magnetic field.

6. The surveying method of claim 5, wherein the first and second global positioning measurements made in (a) and (b) are synchronized.

7. The surveying method of claim 5, wherein the magnetic field of the Earth is measured in (d) using a magnetic field sensor that is substantially aligned with the reference direction determined in (c).

8. The surveying method of claim 5, wherein the magnetic field of the Earth is measured in (d) using a tri-axial magnetic field sensor of which one axis is substantially aligned with the reference direction determined in (c).

9. The surveying method of claim 5, wherein the magnetic field of the Earth is measured in (d) using a tri-axial magnetic field sensor deployed in hot box configured to maintain sensor temperature at a constant temperature in a range from about 25 to about 175 degrees C.

10. The surveying method of claim 5, wherein the first and second surface locations are spaced apart by a distance in a range from about 100 to about 1000 meters.

11. The surveying method of claim 5, wherein the reference direction is determine in (c) by subtracting the first global positioning measurement obtained in (a) from the second global positioning measurement obtained in (b).

12. The surveying method of claim 5, further comprising:

(f) measuring a magnetic field in a subterranean borehole; and

(g) processing the magnetic field measured in (f) with at least one of the magnetic declination and the magnetic inclination of the Earth'"'"'s magnetic field determined in (e) to obtain a magnetic azimuth of the subterranean borehole with respect to true north.

13. The surveying method of claim 5, further comprising:

(f) measuring a magnetic field in a subterranean borehole; and

(g) processing the magnetic field measured in (f) with at least one of the magnetic declination and the magnetic inclination of the Earth'"'"'s magnetic field determined in (e) to obtain an interference magnetic field emanating from another subterranean borehole.

14. The surveying method of claim 5, wherein the first surface location is magnetically clean.

15. The surveying method of claim 14, wherein the first surface location is obtained via making a proton magnetometer scan of a predetermined surface region.

16. The surveying method of claim 5, wherein the magnetic field of the Earth is measured in (d) using first and second tri-axial magnetic field sensors and wherein the method further comprises:

(f) calibrating the first and second magnetometer sets to one another using the magnetic field measurements made in (d).

17. A method for surveying a subterranean borehole, the method comprising:

(a) obtaining a first global positioning measurement at a first surface location;

(b) obtaining a second global positioning measurement at a second surface location;

(c) processing the first and second global positioning measurements obtained in (a) and (b) to determine a reference direction between the first and second surface locations;

(d) measuring a magnetic field of the Earth at the first surface location;

(e) processing the reference direction obtained in (c) and the magnetic field of the Earth measured in (d) to determine at least one of a magnetic declination and a magnetic inclination of the Earth'"'"'s magnetic field

(f) measuring a magnetic field in the subterranean borehole; and

(g) processing the magnetic field measured in (f) with at least one of the magnetic declination and the magnetic inclination of the Earth'"'"'s magnetic field determined in (e) to obtain at least one of a magnetic azimuth of the subterranean borehole with respect to true north and an interference magnetic field emanating from another subterranean borehole.

18. The method of claim 17, wherein the reference direction and a predetermined section of the subterranean borehole are aligned within about 10 degrees of one another.

19. The method of claim 18, wherein the magnetic field of the Earth is measured in (d) using a tri-axial magnetic field sensor of which one axis is substantially aligned with the reference direction determined in (c).

20. The method of claim 18, wherein the predetermined section of the subterranean borehole is substantially horizontal.