Claims
- 1. A method of estimating a subsurface formation's velocity ratio using a bottom hole assembly comprising:
(a) generating a compressional wave having a first wavelength from said bottom hole assembly; (b) detecting a compressional wave received signal using said bottom hole assembly; (c) generating a shear wave having a second wavelength from said bottom hole assembly; (d) detecting a shear wave received signal using said bottom hole assembly; and (e) phase matching said detected compressional and shear wave received signals to determine said velocity ratio.
- 2. The method of claim 1 wherein the ratio of said first wavelength to said second wavelength is approximately two.
- 3. The method of claim 1 wherein the amplitude of said shear wave received signal is adjusted to approximate the amplitude of said compressional wave received signal before said phase matching.
- 4. The method of claim 1 wherein said phase matching involves the matching of individual data points between said shear wave received signal and said compressional wave received signal.
- 5. The method of claim 1 wherein said phase matching involves the matching time intervals between said shear wave received signal and said compressional wave received signal.
- 6. The method of claim 5 wherein said time intervals are approximately of equal width in time.
- 7. The method of claim 5 wherein each said time interval is determined such that the energy level in said shear wave received signal and said compressional wave received signal is approximately constant throughout said interval.
- 8. The method of claim 1 wherein said velocity ratio is used to determine the shear wave velocity of said subsurface formation.
- 9. The method of claim 1 wherein said velocity ratio is used to determine the compressional wave velocity of said subsurface formation.
- 10. The method of claim 8 wherein said shear wave velocity is used to determine the two-way travel time to a reflector in said formation.
- 11. The method of claim 10 wherein said two-way travel time is used to determine the distance to said reflector.
- 12. The method of claim 1 wherein said velocity ratio is used to determine the effective stress of said formation.
- 13. The method of claim 12 wherein said effective stress is used to determine the pore pressure of said formation.
- 14. The method of claim 13 wherein said pore pressure is calculated as a function of depth.
- 15. A method of estimating a subsurface formation's velocity ratio using a bottom hole assembly comprising:
(a) generating a compressional wave having a first wavelength from said bottom hole assembly; (b) detecting a compressional wave received signal using said bottom hole assembly; (c) generating a shear wave having a second wavelength from said bottom hole assembly, said second wave length being approximately one-half of said first wavelength; (d) detecting a shear wave received signal using said bottom hole assembly; and (e) phase matching said detected compressional and shear wave received signals to determine said velocity ratio, said phase matching involves the matching time intervals between said shear wave received signal and said compressional wave received signal.
- 16. The method of claim 15 wherein said velocity ratio is used to determine the shear wave velocity of said subsurface formation.
- 17. The method of claim 15 wherein said velocity ratio is used to determine the compressional wave velocity of said subsurface formation.
- 18. The method of claim 16 wherein said shear wave velocity is used to determine the two-way travel time to a reflector in said formation.
- 19. The method of claim 18 wherein said two-way travel time is used to determine the distance to said reflector.
- 20. The method of claim 15 wherein said velocity ratio is used to determine the effective stress of said formation.
- 21. The method of claim 20 wherein said effective stress is used to determine the pore pressure of said formation.
- 22. The method of claim 21 wherein said pore pressure is calculated as a function of depth.
- 23. A method of continuously estimating the pore pressures of formations ahead of a bottom hole assembly, comprising the steps of
(a) generating a compressional wave having a first wavelength from said bottom hole assembly; (b) detecting a compressional wave received signal using said bottom hole assembly; (c) generating a shear wave having a second wavelength from said bottom hole assembly, said second wave length being approximately one-half of said first wavelength; (d) detecting a shear wave received signal using said bottom hole assembly; (e) phase matching said detected compressional and shear wave received signals to determine said velocity ratio, said phase matching involves the matching time intervals between said shear wave received signal and said compressional wave received signal; (f) using said velocity ratio to determine the effective stress of a formation ahead of said bottom hole assembly; and (g) using said effective stress to determine said pore pressures of said formations ahead of said bottom hole assembly; repeating steps (a) though (g) as said bottom hole assembly moves sequentially downward through said formations.
- 24. A method of continuously monitoring the wellbore pressure safety margin corresponding to formations ahead of a bottom hole assembly, comprising the steps of generating a compressional wave having a first wavelength from said bottom hole assembly;
(a) detecting a compressional wave received signal using said bottom hole assembly; (b) generating a shear wave having a second wavelength from said bottom hole assembly, said second wave length being approximately one-half of said first wavelength; (c) detecting a shear wave received signal using said bottom hole assembly; (d) phase matching said detected compressional and shear wave received signals to determine said velocity ratio, said phase matching involves the matching time intervals between said shear wave received signal and said compressional wave received signal; (e) Using said velocity ratio to determine the effective stress of a formation ahead of said bottom hole assembly; (f) Using effective stress to determine the pore pressure of said formation ahead of said bottom hole assembly; (g) Using said pore pressure to determine the wellbore pressure safety margin of a formation ahead of said bottom hole assembly; and (h) repeating steps (a) though (h) as said bottom hole assembly moves sequentially downward through said formations.
- 25. A method of continuously optimizing the weight of drilling mud used in a drilling operation, comprising the steps of:
(a) detecting a compressional wave received signal using said bottom hole assembly; (b) generating a shear wave having a second wavelength from said bottom hole assembly, said second wave length being approximately one-half of said first wavelength; (c) detecting a shear wave received signal using said bottom hole assembly; (d) phase matching said detected compressional and shear wave received signals to determine said velocity ratio, said phase matching involves the matching time intervals between said shear wave received signal and said compressional wave received signal; (e) using said velocity ratio to determine the effective stress of a formation ahead of said bottom hole assembly; (f) using effective stress to determine the pore pressure of said formation ahead of said bottom hole assembly; and (g) using said pore pressure to specify a weight of said drilling mud which corresponds to a target wellbore pressure safety margin.
Parent Case Info
[0001] This application is a continuation-in-part of U.S. application Ser. No. 09/686,735 filed Oct. 10, 2000, now abandoned, and of co-pending U.S. application Ser. No. 09/973,529 filed Oct. 9, 2001.
Continuation in Parts (2)
|
Number |
Date |
Country |
Parent |
09973529 |
Oct 2001 |
US |
Child |
10318786 |
Dec 2002 |
US |
Parent |
09686735 |
Oct 2000 |
US |
Child |
09973529 |
Oct 2001 |
US |