Elastic full wavefield inversion with refined anisotropy and V
Methods for inversion of seismic data to infer subsurface physical property parameters, comprising constructing an inhomogeneous anisotropy model and/or inhomogeneous V S /V P or V P /V S model; and inverting the seismic data in a sequential or simultaneous approach to obtain at least one subsurface physical property parameter using an elastic inversion algorithm and the inhomogeneous anisotropy model and/or inhomogeneous V S /V P or V P /V S model. Constructing an inhomogeneous anisotropy model may comprise deriving geobodies from at least one of seismic facies analysis, regional geologic information, or seismically derived earth models; and adjusting at least one of ε, δ, γ, or parameters of the elastic stiffness tensor matrix in a homogeneous anisotropy model in areas corresponding to the geobodies. Constructing an inhomogeneous V S /V P or V P /V S model may comprise deriving geobodies and adjusting values in a homogeneous V S /V P or V P /V S model in areas corresponding to the geobodies.
1. A method for prospecting for hydrocarbons using inversion of seismic data to infer subsurface physical property parameters comprising:
constructing an inhomogeneous anisotropy model;
inverting the seismic data in a sequential or simultaneous approach to obtain at least one subsurface physical property parameter using an elastic inversion algorithm and the inhomogeneous anisotropy model; and
wherein the subsurface physical property parameters comprise P-wave velocity V P , S-wave velocity V s , density, and combinations thereof;
identifying potential hydrocarbon-bearing formations in a subsurface region based on the physical property parameter; and
causing a well to be drilled that targets the potential hydrocarbon-bearing formations.
2. The method of claim 1 , wherein using an elastic inversion algorithm comprises:
extracting only PP mode data from the seismic data;
inverting the PP mode data sequentially in two or more different offset ranges, each offset range inversion determining P-wave impedance (I p ) and at least one of S- wave impedance (I s ), P-wave velocity over S-wave velocity (V p /V s ), S-wave velocity over P-wave velocity (V s /V p ), and S-wave velocity (V s ), wherein in a second and subsequent inversions, parameters determined in a previous inversion are held fixed; and
using the inverted subsurface physical property parameters to construct the inhomogeneous anisotropy model.
3. The method of claim 2 , wherein a near-offset range is sequentially first to be inverted to infer I P , using a computer programmed with an acoustic or elastic inversion algorithm.
4. The method of claim 3 , wherein a mid-offset range is sequentially second to be inverted to infer at least one of Is, V p /V s , V s /V p , and V s , with I P fixed at its value from the first inversion, said second inversion using an elastic inversion algorithm.
5. The method of claim 4 , wherein inverting the seismic data is performed in a sequential approach comprising:
inverting a far-offset range to infer density or V P , using an elastic inversion algorithm, with I P fixed at its value from the inversion of the near-offset range and I P or V p /V S or V s /V p or V S fixed at its value from the inversion of the mid-offset range.
6. The method of claim 5 , wherein density ρ is inferred, and further comprising:
computing V P from the relationship I P =ρV P using I P and the inferred density.
7. The method of claim 5 , wherein V P is inferred, and further comprising:
computing density ρ from the relationship I P =ρV P using I P and the inferred V P .
8. The method of claim 5 , further comprising repeating the inversions of the near-offset data, mid-offset data, and far-offset data at least one time to update the inferred physical property parameters.
9. The method of claim 4 , wherein the acoustic and elastic inversion algorithms are full waveform inversion algorithms.
10. The method of claim 1 , wherein constructing the inhomogeneous anisotropy model comprises:
deriving geobodies from at least one of seismic facies analysis, regional geologic information, or seismically derived earth models; and
adjusting at least one of the elastic stiffness tensor matrix in a homogeneous anisotropy model in areas corresponding to the geobodies.
11. The method of claim 10 , wherein the geobodies are sand geobodies.
12. A method for prospecting for hydrocarbons using inversion of seismic data to infer subsurface physical property parameters comprising:
constructing an inhomogeneous anisotropy model and an inhomogeneous V S /V P or V P /V S model;
inverting the seismic data in a sequential or simultaneous approach to obtain at least one subsurface physical property parameter using an elastic inversion algorithm and the inhomogeneous anisotropy model and the inhomogeneous V S /V P or V P /V S model;
wherein the subsurface physical property parameters comprise P-wave velocity V P , S-wave velocity V S , density, lambda, mu, and combinations thereof;
identifying potential hydrocarbon-bearing formations in a subsurface region based on the physical property parameter; and
causing a well to be drilled that targets the potential hydrocarbon-bearing formations.
13. The method of claim 12 , wherein using an elastic inversion algorithm comprises:
extracting only PP mode data from the seismic data;
inverting the PP mode data sequentially in two or more different offset ranges, each offset range inversion determining P-wave impedance (I P ) and at least one of S-wave impedance (I S ), P-wave velocity over S-wave velocity (V P /V S ), S-wave velocity over P-wave velocity (V S /V P ), and S-wave velocity (V S ), wherein in a second and subsequent inversions, parameters determined in a previous inversion are held fixed; and
using the inverted subsurface physical property parameters to construct the inhomogeneous anisotropy model and the inhomogeneous V S /V P or V P /V S model.
14. The method of claim 13 , wherein a near-offset range is sequentially first to be inverted to infer I P , using a computer programmed with an acoustic or elastic inversion algorithm.
15. The method of claim 14 , wherein a mid-offset range is sequentially second to be inverted to infer at least one of I S , V P /V S , V S /V P , and V S , with I P fixed at its value from the first inversion, said second inversion using an elastic inversion algorithm.
16. The method of claim 15 , wherein inverting the seismic data is performed in a sequential approach comprising:
inverting a far-offset range to infer density or V P , using an elastic inversion algorithm, with I P fixed at its value from the inversion of the near-offset range and I P or V P /V S or V S /V P or V S fixed at its value from the inversion of the mid-offset range.
17. The method of claim 16 , wherein density ρ is inferred, and further comprising:
computing V P from the relationship I P =ρV P using I P and the inferred density.
18. The method of claim 16 , wherein V P is inferred, and further comprising:
computing density ρ from the relationship I P =ρV P using I P and the inferred V P .
19. The method of claim 16 , further comprising repeating the inversions of the near-offset data, mid-offset data, and far-offset data at least one time to update the inferred physical property parameters.
20. The method of claim 15 , wherein the acoustic and elastic inversion algorithms are full waveform inversion algorithms.
21. The method of claim 12 , wherein constructing the inhomogeneous anisotropy model comprises:
deriving geobodies from at least one of seismic facies analysis, regional geologic information, or seismically derived earth models; and
adjusting parameters of the elastic stiffness tensor matrix in a homogeneous anisotropy model in areas corresponding to the geobodies.
22. The method of claim 21 , wherein the geobodies are sand geobodies.
23. The method of claim 12 , wherein constructing the inhomogeneous V S /V P or V P /V S to model comprises:
deriving geobodies from at least one of seismic facies analysis, regional geologic information, or seismically derived earth models; and
adjusting values in a homogeneous V S /V P or V P /V S model in areas corresponding to the geobodies.
24. The method of claim 23 , wherein the geobodies are sand geobodies, and areas corresponding to sand are assigned lower V P /V S values if constructing a V P /V S model or assigned higher V S /V P values if constructing a V S /V P model.
25. A method for prospecting for hydrocarbons using inversion of seismic data to infer subsurface physical property parameters comprising:
constructing an inhomogeneous V S /V P or V P /V S model;
inverting the seismic data in a sequential or simultaneous approach to obtain at least one subsurface physical property parameter using an elastic inversion algorithm and the inhomogeneous V S /V P or V P /V S model;
wherein the subsurface physical property parameters comprise P-wave velocity V P , S-wave velocity V S , density, lambda, mu, and combinations thereof;
identifying potential hydrocarbon-bearing formations in a subsurface region based on the physical property parameter; and
causing a well to be drilled that targets the potential hydrocarbon-bearing formations.
26. The method of claim 25 , wherein using an elastic inversion algorithm comprises:
extracting only PP mode data from the seismic data;
inverting the PP mode data sequentially in two or more different offset ranges, each offset range inversion determining P-wave impedance (I P ) and at least one of S-wave impedance (I S ), P-wave velocity over S-wave velocity (V P V S ), S-wave velocity over P-wave velocity (V S /V P ), and S-wave velocity (V S ), wherein in a second and subsequent inversions, parameters determined in a previous inversion are held fixed; and
using the inverted subsurface physical property parameters to construct the inhomogeneous V S /V P or V P /V S model.
27. The method of claim 26 , wherein a near-offset range is sequentially first to be inverted to infer I P , using a computer programmed with an acoustic or elastic inversion algorithm.
28. The method of claim 27 , wherein a mid-offset range is sequentially second to be inverted to infer at least one of I S , V P /V S , V S /V P , and V S , with I P fixed at its value from the first inversion, said second inversion using an elastic inversion algorithm.
29. The method of claim 28 , wherein inverting the seismic data is performed in a sequential approach comprising:
inverting a far-offset range to infer density or V P , using an elastic inversion algorithm, with I P fixed at its value from the inversion of the near-offset range and I P or V P /V S or V S /V P or V S fixed at its value from the inversion of the mid-offset range.
30. The method of claim 29 , wherein density ρ is inferred, and further comprising:
computing V P from the relationship I P =ρV P using I P and the inferred density.
31. The method of claim 29 , wherein V P is inferred, and further comprising:
computing density ρ from the relationship I P =ρV P using I P and the inferred V P .
32. The method of claim 29 , further comprising repeating the inversions of the near-offset data, mid-offset data, and far-offset data at least one time to update the inferred physical property parameters.
33. The method of claim 28 , wherein the acoustic and elastic inversion algorithms are full waveform inversion algorithms.
34. The method of claim 25 , wherein constructing the inhomogeneous V S /V P or V P /V S model comprises:
deriving geobodies from at least one of seismic facies analysis, regional geologic information, or seismically derived earth models; and
adjusting values in a homogeneous V S /V P or V P /V S model in areas corresponding to the geobodies.
35. The method of claim 34 , wherein the geobodies are sand geobodies, and areas corresponding to sand are assigned lower V P /V S values if constructing a V P /V S model or assigned higher V S /V P values if constructing a V S /V P model.