DOWNHOLE MEASUREMENT OF FORMATION CHARACTERISTICS WHILE DRILLING

• US 20090049889A1
• Filed: 10/29/2008
• Published: 02/26/2009
• Est. Priority Date: 12/19/2005
• Status: Active Grant

• Current Assignee: Schlumberger (Schlumberger NV)
• Original Assignee: Schlumberger (Schlumberger NV)
• Inventors: Taherian, Reza, Poitzsch, Martin E., Tabanou, Jacques R., POP, JULIAN J.
• Granted Patent: US 8,056,408 B2
• Time in Patent Office: Days
• US Class Current: 73/19.90
• CPC Class Codes: E21B 49/005 Testing the nature of borehole walls or the formation by using drilling mud or cutting data
• CPC Class Codes: E21B 49/081 with down-hole means for trapping a fluid sample E21B49/10 takes precedence

Abstract

A method for determining a property of formations surrounding an earth borehole being drilled with a drill bit at the end of a drill string, using drilling fluid that flows downward through the drill string, exits through the drill bit, and returns toward the earth'"'"'s surface in the annulus between the drill string and the periphery of the borehole, including the following steps: obtaining, downhole near the drill bit, a pre-bit sample of the mud in the drill string as it approaches the drill bit; obtaining, downhole near the drill bit, a post-bit sample of the mud in the annulus, entrained with drilled earth formation, after its egression from the drill bit; implementing pre-bit measurements on the pre-bit sample; implementing post-bit measurements on the post-bit sample; and determining a property of the formations from the post-bit measurements and the pre-bit measurements.

Claims

1. A method of determining whether non-hydrocarbon gas exists in a formation surrounding an earth borehole being drilled with a drill bit at the end of a drill string, using drilling fluid that flows downward through the drill string, exits through the drill bit, and returns toward the earth'"'"'s surface in the annulus between the drill string and the periphery of the borehole, comprising the steps of:

obtaining, downhole near the drill bit, a pre-bit sample of the mud in the drill string as it approaches the drill bit;

obtaining, downhole near the drill bit, a post-bit sample of the mud in the annulus, entrained with drilled earth formation, after its egression from the drill bit;

implementing pre-bit measurements on the pre-bit sample;

implementing post-bit measurements on the post-bit sample; and

determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation.

2. The method of claim 1 wherein determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation includes determining from the pre-bit measurements and the post-bit measurements whether CO₂ gas exists in the formation.

3. The method of claim 1 wherein determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation includes determining from the pre-bit measurements and the post-bit measurements whether He gas exists in the formation.

4. The method of claim 1 wherein determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation includes determining from the pre-bit measurements and the post-bit measurements whether H₂S gas exists in the formation.

5. The method of claim 1 wherein determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation includes determining from the pre-bit measurements and the post-bit measurements whether N₂ gas exists in the formation.

6. The method of claim 1 wherein determining from the pre-bit measurements and the post-bit measurements whether non-hydrocarbon gas exists in the formation includes determining from the pre-bit measurements and the post-bit measurements whether H₂S gas and at least one of CO₂ gas, He gas, and N₂ gas exist in the formation.

7. The method of claim 1 wherein the steps of implementing pre-bit measurements on the pre-bit sample and implementing post-bit measurements on the post-bit sample are performed downhole.

8. The method of claim 1 wherein the step of determining whether non-hydrocarbon gas exists in the formation comprises examining at least one of a ratio, a comparison, and a difference of the pre-bit measurements and the post-bit measurements.

9. The method of claim 1 wherein the step of determining whether non-hydrocarbon gas exists in the formation is performed downhole.

10. The method of claim 9 further comprising transmitting uphole one of the determination of whether non-hydrocarbon gas exists in the formation, the pre-bit measurements, the post-bit measurements, and combinations thereof.

11. The method of claim 1 wherein the step of determining whether non-hydrocarbon gas exists in the formation comprises determining the composition of one of the pre-bit sample, the post-bit sample, and combinations thereof.

12. The method of claim 1 wherein the step of implementing post-bit measurements on the post-bit sample comprises using downhole at least one of mass spectrometry, optical spectrometry, Fourier Transform Infrared Spectroscopy (FTIR), gas chromatograph FTIR (GC-FTIR), gas chromatograph mass spectrometry (GC-MS) ultraviolet spectroscopy, fluorescence spectroscopy, nuclear magnetic resonance (NMR), and a molecular sieve.

13. A method of determining whether non-hydrocarbon gas exists in a formation surrounding an earth borehole being drilled with a drill bit at the end of a drill string, using drilling fluid that flows downward through the drill string, exits through the drill bit, and returns toward the earth'"'"'s surface in the annulus between the drill string and the periphery of the borehole, comprising the steps of:

obtaining, downhole near the drill bit, a post-bit sample of the mud in the annulus, entrained with drilled earth formation, after its egression from the drill bit;

implementing downhole post-bit measurements on the post-bit sample, including separating solid components and at least a portion of fluid components of the post-bit sample; and

analyzing at least one of the separated components to determine whether non-hydrocarbon gas exists in the formation.

14. The method of claim 13 wherein the step of separating solid components and at least a portion of fluid components of the post-bit sample includes heating the post-bit sample to obtain a vapor, and analyzing the vapor.

15. The method of claim 14 further comprising repeating the heating the fluid components and analyzing the vapor steps at a higher temperature.

16. The method of claim 13 wherein the step of separating solid components and at least a portion of fluid components of the post-bit sample is implemented using selective membranes.

17. The method of claim 13 wherein the step of separating solid components and at least a portion of fluid components of the post-bit sample includes expanding a volume of the post-bit sample.

18. The method of claim 13 wherein the step of implementing post-bit measurements on the post-bit sample comprises using downhole at least one of mass spectrometry, optical spectrometry, FTIR, GC-FTIR, GC-MS ultraviolet spectroscopy, fluorescence spectroscopy, NMR, and a molecular sieve.

19. The method of claim 13 further comprising:

obtaining, downhole near the drill bit, a pre-bit sample of the mud in the drill string as it approaches the drill bit; and

determining the composition of one of the pre-bit sample, the post-bit sample, and combinations thereof.

20. The method of claim 19 further comprising transmitting uphole one of the determination of whether non-hydrocarbon gas exists in the formation, the pre-bit measurements, the post-bit measurements, and combinations thereof.

21. A method of determining whether non-hydrocarbon gas exists in a formation surrounding an earth borehole being drilled with a drill bit at the end of a drill string, using drilling fluid that flows downward through the drill string, exits through the drill bit, and returns toward the earth'"'"'s surface in the annulus between the drill string and the borehole, comprising the steps of:

obtaining, downhole near the drill bit, a post-bit sample of the mud in the annulus, entrained with drilled earth formation, after its egression from the drill bit; and

implementing downhole post-bit measurements on the post-bit sample with a mass spectrometer to determine whether non-hydrocarbon gas exists in the formation.

22. The method of claim 21 further comprising transmitting uphole at least one of the post-bit measurements and the determination of whether non-hydrocarbon gas exists in the formation.

23. The method of claim 21 further comprising separating volatile components of the post-bit sample, and implementing downhole post-bit measurements on the separated volatile components.

24. The method of claim 21 wherein the step of separating volatile components of the post-bit sample includes expanding a volume of the post-bit sample.

25. The method of claim 21 wherein the step of separating volatile components of the post-bit sample includes heating the post-bit sample to obtain a vapor, and analyzing the vapor.

26. The method of claim 21 further comprising determining at least a C1-C8 compositional analysis on the post-bit sample.

27. The method of claim 21 wherein the mass spectrometer is a quadrupole mass spectrometer.