Method of generating seismic wavelets using seismic range equation

• US 5,173,880 A
• Filed: 11/08/1990
• Issued: 12/22/1992
• Est. Priority Date: 12/26/1989
• Status: Expired due to Fees

• Current Assignee: Exxon Production Research Company (Exxon Mobil Corporation)
• Original Assignee: Exxon Production Research Company (Exxon Mobil Corporation)
• Inventors: Zimmerman, Carol J., Duren, Richard E.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US07/610,467
• Time in Patent Office: 775 Days
• Field of Search: 364/73, 364/421, 367/21, 367/38, 367/73, 367/48, 367/22, 367/23, 367/24, 367/47
• US Class Current: 367/73
• CPC Class Codes: G01V 1/282 Application of seismic models, synthetic seismograms

Abstract

A method of deterministically computer generating a model of a response voltage waveform of a seismic receiver employed in a seismic, particularly marine, data gathering system, the model incorporating factors that have been identified as significant contributions to amplitude, such as directivity, divergence, attenuation, interbed multiples, and transmissivity. The model is generated from the mathematical manipulation of well log data and data gathering system characteristics into a seismic range equation, namely: ##EQU1## where E_r (f)=received energy density

E(f)=radiated energy density

D(θ_s, φ_s, f)=source directivity along θ_s, φ_s direction at the source

A_c (θ_H, φ_H, f)=Capture area along θ_H, φ_H direction at the hydrophone array

R_T =target reflection coefficient

D_v =divergence ##EQU2## One preferred use of the resulting modeled waveform is in a pre-process comparison with actual seismic data for validating and interpreting such actual data. Another use is in the deconvolution of seismic data for improved resolution.

Claims

1. A method of modeling an amplitude spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining values for the factors corresponding to the source, the medium, the target, and the receiving system, said factors including radiated energy density, directivity, capture area, target reflection coefficient, divergence, and loss factor, and

combining said values for said factors simultaneously in one concise analytical formulation to produce a model amplitude spectrum of the seismic wavelet.

2. A method, in accordance with claim 1, wherein said model amplitude spectrum is modeled by utilizing the following seismic range equation:

##EQU26## having seven elements wherein;

     1) E(f) is the radiated energy density from the source at frequency, f;

2) D(θ

_s,φ

_s,f) is source directivity along the θ

_s, φ

_s direction;

3) A_c (θ

_H,φ

_H,f) is the capture area of the receiving system for incident angle θ

_H,φ

_H ;

4) R_T is the P-wave reflection coefficient of the target interface;

5) D_v is the divergence;

6) L(f) is representative of the losses associated with the subsurface; and

7) E_p (f) is the received energy density at the receiving system,

said method comprising

determining the physical subsurface characteristics, for the subsurface layers (i) transversed by the seismic wavelet, including the P-wave velocity (α

_i), S-wave velocity (β

_i), density (ρ

_i), and thickness (h_i), assuming the seismic wavelet path begins at the source of a seismic data gathering system, at frequency (f), through the medium at ray angle (θ

_s) with respect to the normal to the surface and at corresponding ray angles (θ

_i) to the predetermined target bed at depth (d), returning through the medium to the receiving system,

determining the parameters of the seismic data gathering system, including, a frequency spectrum of the radiated waveforms from the individual array elements, number of source array elements, said number being at least one, position of the source array elements, when said number of elements is greater than one, value of any firing delays associated with source array elements (δ

_n), the value of any receiving array and load impedances (Z_H (f) and Z_L (f)), receiving array sensitivity (S_H (f)), and the receiving array depth (d_H),

calculating the radiated energy density E(f),

calculating the source directivity D(θ

_s,φ

_s,f),

calculating the capture area (A_c (θ

_H,φ

_H, f)) along the incident direction at the receiving array,

determining the target'"'"'s power reflection coefficient (R_T²),

calculating the divergence (D_v) for a given offset,

calculating the loss factor (L(f)),

dividing the product of the radiated energy density (E(f)), the source directivity D(θ

_s,θ

_s,f), the capture area A_c (θ

_h,φ

_h,f), the target power reflection coefficient (R_T²), by the divergence (D_v), and the loss factor (L(f)), to form the received energy density (E_p (f)), and

deriving said model amplitude spectrum (|A_p (f)|) of said model seismic wavelet, for all frequencies across the seismic band, utilizing said received energy density (E_p (f)) and said value of any load impedance.

3. A method in accordance with claim 2, wherein said radiated energy density is derived from a number of said source array elements (N), said frequency (f), said seismic velocity of first layer traversed (α

₁), said density of the first layer transversed (ρ

_i), and from an illumination factor.

4. A method in accordance with claim 3, wherein said illumination factor (I_n (f)) is derived from said frequency spectrum (A_n (f)) of the radiated waveforms, said value of any firing delay (δ

_n), and said frequency (f).

5. A method in accordance with claim 2, wherein said source directivity is derived from the ratio of said radiated energy density per unit solid angle radiated in a particular direction (θ

_s,φ

_s) to said radiated energy density E(f).

6. A method in accordance with claim 2, wherein said capture area is derived from the multiplication of a capture area along an acoustic axis normal to the surface and a transmitting pattern of said receiving array.

7. A method in accordance with claim 6, wherein said capture area along the direction of an acoustic axis normal to the surface, is derived from said receiving array sensitivity S_H (f), said value of any load and receiving array impedances (Z_L (f) and Z_H (f)), said density of the first transversed layer, said P-wave velocity of the first transversed layer, and said receiving array depth.

8. A method in accordance with claim 6, wherein said transmitting pattern is defined by the ratio of the receiving array directivity (D(θ

_H,φ

_H,f) along the incident ray direction to a directivity of the receiving array along the acoustic axis (D(O,φ

_H,f).

9. A method in accordance with claim 2, wherein said target'"'"'s reflection coefficient is derived from the said angle of incidence (θ

_i), said seismic velocities (α

_i,α

_i+1,β

_i and β

_i+1), and said densities (ρ

_i and ρ

_i+1) of layers at the interface.

10. A method in accordance with claim 2, wherein said divergence is derived from said thickness (h_i) of subsurface layers transversed by the seismic wavelet, said ray angle (θ

_i) in each subsurface layer, and said offset X between source and receiver.

11. A method in accordance with claim 2, wherein said loss factor includes transmission loss (L_t).

12. A method in accordance with claim 11, wherein said transmission loss (L_t) is the loss associated with crossing the interfaces twice and is derived from the transmission coefficients (T_i,i+1, T_i+1,i) associated with the corresponding layers traversed.

13. A method in accordance with claim 12, wherein said interfaces include solid-to-solid interfaces, a fluid-to-solid interface, and a solid-to-fluid interface.

14. A method in accordance with claim 2, wherein said loss factor includes Q-loss (L_Q (f)).

15. A method in accordance with claim 14, wherein said Q-loss is derived from an attenuation constant (Q_i) for each transversed subsurface layer, said P-wave velocity (α

_i) of each transversed subsurface layer, said thickness of each transversed subsurface layer (h_i), said frequency (f), and said ray angle (θ

_i).

16. A method in accordance with claim 15, wherein said attenuation constant for each said subsurface layer is estimated by finding an effective attenuation constant (Q) down to said target depth from existing seismic data in the area.

17. A method of modeling a phase spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by the seismic wavelet,

deriving the value of any phase components of load and receiving array impedances, and

combining said phase components of said electromotive force and said load and receiving array impedances to produce a metal phase spectrum of the seismic wavelet.

18. A method in accordance with claim 17, wherein said phase components of said electromotive force φ

.sub.ε

(f) are derived from a sum of the phase spectrum of receiver sensitivity φ

_s (f), the phase spectrum of an incident pressure pulse on the receiver array A(θ

_H,φ

_H, f) , and a phase contribution due to the presence of the image array, assuming the receiving array is at depth d_H.

19. A method in accordance with claim 18, wherein said phase spectrum of a pressure pulse incident on the receiver array is derived from a radiated far-field source pulse phase spectrum φ

_o (f) combined with a phase spectrum contribution of the earth filter.

20. A method in accordance with claim 19, wherein said radiated far-field source pulse is derived from individual frequency spectra A_n (f), element geometry (r_n), value of any firing delay (δ

_n), and direction θ

_s, φ

_s.

21. A method in accordance with claim 19, wherein said earth filter includes a Q-loss filter.

22. A method of modeling a frequency spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining values for factors corresponding to the source, the medium, the target, and the receiving system, said factors including radiated energy density, directivity, capture area, target reflection coefficient, divergence, and loss factor,

combining said values for said factors to produce a model amplitude spectrum of the seismic wavelet,

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by the seismic wavelet,

deriving the value of any phase components of load and receiving array impedances,

combining said components of said electromotive force and said load and receiving array impedances to produce a model phase spectrum of the seismic wavelet, and

combining said model amplitude spectrum with said model phase spectrum to produce a model frequency spectrum of the seismic wavelet.

23. A method of determining the effect of an offset variation in an analog receiving and recording system that would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining a capture area along the acoustic axis for a source-to-receiver offset,

determining additional capture areas along the acoustic axis for other source-to-receiver offsets, and

finding the ratio of said capture area to said additional capture areas and said capture area to determine an offset variation in the analog receiving and recording system.

24. A method of determining a transmitting pattern of a receiving array to show the effect of the receiving array and an image array (or ghost reflection) that affects an amplitude spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining the directivity of the receiving array along an incident direction,

determining the directivity of the receiving array along an acoustic axis, and

taking the ratio of said directivity of the receiving array along the incident direction to said directivity of the receiving array along the acoustic axis to determine a transmitting pattern of the receiving array.

25. A method of determining a phase component of an array image that affects a phase spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining an incident angle of the seismic wavelet,

determining a cable depth in water,

combining said incident angle and said cable depth in water to provide a time delay associated with the array image, and

determining the phase component associated with the array image from said time delay.

26. A method of modeling an amplitude spectrum of a downgoing interbed multiple that would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining a ray path of the downgoing interbed multiple that would be received by a seismic data gathering system,

determining value for factors corresponding to the source, the medium that would be transversed by the downgoing interbed multiple, the target, and the receiving system, said factors including radiated energy density, directivity, capture area, reflection coefficients, divergence, and loss factor, and

combining said values for said factors to produce a model amplitude spectrum of the downgoing interbed multiple.

27. A method of modeling an amplitude spectrum of an downgoing interbed multiple that would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining a ray path of the upgoing interbed multiple that would be received by a seismic data gathering system,

determining value for factors corresponding to the source, the medium that would be transversed by the upgoing interbed multiple, the target, and the receiving system, said factors including radiated energy density, directivity, capture area, reflection coefficients, divergence, and loss factor, and

combining said values for said factors to produce a model amplitude spectrum of the downgoing interbed multiple.

28. A method of modeling a phase spectrum of a downgoing interbed multiple that would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining a ray path of the downgoing interbed multiple that would be received by a seismic data gathering system,

determining phase components of an electromotive force (φ

₆₈ (f)) generated by the downgoing interbed multiple,

deriving the value of any phase components of load and receiving array impedances, and

combining said phase components of said electromotive force and said load and receiving array impedances to produce a model phase spectrum of the downgoing interbed multiple.

29. A method of modeling a phase spectrum of an upgoing interbed multiple that would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining a ray path of the upgoing interbed multiple that would be received by a seismic data gathering system,

determining phase components of an electromotive force (φ

₆₈ (f)) generated by the upgoing interbed multiple,

deriving the value of any phase components of load and receiving array impedances, and

combining said phase components of said electromotive force and said load and receiving array impedances to produce a model phase spectrum of the upgoing interbed multiple.

30. A method for modeling an interbed multiple loss factor that would affect a primary seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

selecting a number J_max representing a number of subsurface layers an interbed multiple will cross after being reflected once, but before being reflected again,

determining a frequency spectrum for the primary seismic wavelet,

determining a frequency spectrum for each downgoing interbed multiple associated with each subsurface layer down to a target layer, assuming J_max +1 interbed multiples will be generated per said subsurface layer,

determining a frequency spectrum for each upgoing interbed multiple associated with each subsurface layer down to a target layer, assuming J_max +1 interbed multiples will be generated per said subsurface,

determining downgoing ratios by dividing said frequency spectrum for each downgoing interbed multiple by said frequency spectrum for the primary seismic wavelet,

determining upgoing ratios by dividing said frequency spectrum for each upgoing interbed multiple by said frequency spectrum of said primary seismic wavelet,

taking the reciprocal of the squared magnitude of the sum of 1, the sum of said downgoing ratios, and the sum of said upgoing ratios (eliminating redundancy) to determine the interbed multiple loss factor.

31. A method in accordance with claim 30, wherein said selecting of said number J_max includes

assuming a downgoing interbed multiple following a downgoing secondary ray path beginning at the source at ray angle (θ

_d), at frequency (f), through a predetermined number of subsurface layers, to layer (i), up through a predetermined number of interfaces (J), down to the target at said depth (d), up through the subsurface layers to the receiving system, and

assuming an upgoing interbed multiple following an upgoing secondary ray path beginning at the source at ray angle (θ

_u), at a frequency (f), down to the target at said depth (d), up to a predetermined subsurface layer (i), down a predetermined number of interfaces (J), then back up through the subsurface layers to the receiving system.

32. A method for modeling an unprocessed seismic trace, said method comprising

determining values for factors corresponding to the source, the medium that would be transversed by a seismic wavelet, the target, and the receiving system that would affect said seismic wavelet, said factors including, source-to-receiver offset, radiated energy density, directivity, capture area, target reflection coefficient, divergence, and loss factor,

combining said values for said factors to produce a model amplitude spectrum of said seismic wavelet,

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by said seismic wavelet,

deriving the value of any phase component of load and receiver array impedances,

combining said components of said electromotive force and said load and receiver array impedances to produce a model phase spectrum of said seismic wavelet,

combining said model amplitude spectrum with said model phase spectrum to produce a model frequency spectrum for a model seismic wavelet for said source-to-receiver offset,

determining a time-reflection sequence from a parallel layered subsurface, and

convolving said model seismic wavelet with said time reflection sequence to develop a model of the unprocessed seismic trace for said source-to-receiver offset.

33. A method of affecting an enhanced amplitude-versus-offset analysis by comparing unprocessed seismic data and modeled data, said method comprising

generating a model of an unprocessed seismic trace at a source-to-receiver offset,

generating several models of unprocessed seismic traces for other source-to-receiver offsets corresponding to those recorded for the seismic data,

combining said models for said source-to-receiver offsets to develop an unprocessed model gather, and

comparing variations in the amplitude versus offset of unprocessed seismic data to variations in amplitude versus offset of said unprocessed model gather for corresponding source-to-receiver offsets.

34. A method of affecting an enhanced amplitude-versus-offset analysis on recorded seismic data wherein the seismic data and modeled data are processed and compared at any step therein, said method comprising

generating a model of an unprocessed seismic trace for a source-to-receiver offset,

generating a plurality of additional models of unprocessed seismic traces for other source-to-receiver offsets corresponding to those recorded for the recorded seismic data,

combining said models for source-to-receiver offsets to develop an unprocessed model gather,

processing said unprocessed model gather to produce a processed model gather,

processing the recorded seismic data to produce processed seismic data, and

comparing variations in the amplitude versus offset of said processed seismic data to variations in amplitude versus offset of said processed model gather.

35. A method in accordance with claim 34, wherein said processing of both said unprocessed model gather and said processing of the recorded seismic data, includes

deconvolving said unprocessed model gather with model seismic wavelets for corresponding source-to-receiver offsets to produce a processed model gather, and

deconvolving the recorded seismic data with said model seismic wavelets for corresponding source-to-receiver offsets to produce a processed seismic gather.

36. A method in accordance with claim 35, wherein said processing of both said unprocessed model gather and the recorded seismic data incorporates an average amplitude correction factor method, said method comprising

determining an average amplitude spectrum of a model seismic wavelet for one source-to-receiver offset for a frequency band,

determining average amplitude for each of said source-to-receiver offsets for said frequency band,

calculating the average amplitude correction factor for each source-to-receiver offset from the ratios of said average amplitude spectrum to said average amplitudes,

multiplying said average amplitude correction factors by said unprocessed model gather at corresponding source-to-receiver offsets, and

multiplying said average amplitude correction factors by the recorded seismic data at corresponding source-to-receiver offsets.

37. A method in accordance with claim 34, wherein said processing of both said unprocessed model gather and the recorded seismic data incorporates a zero phase filtering method, said method comprising

determining an amplitude spectrum for said model seismic wavelet for a source-to-receiver offset corresponding to one in the recorded seismic data and frequency band,

determining an amplitude spectrum for each model seismic wavelet at each source-to-receiver offset corresponding to those in the recorded seismic data for said frequency band to determine overall amplitude spectra,

calculating zero phase filters from the ratio of the amplitude spectrum to said amplitude spectra, and

multiplying the zero phase filters by the unprocessed model gather and the recorded seismic data in said frequency band at the corresponding source-to-receiver offsets.

38. A prestack deconvolution method of processing seismic data, said method comprising

determining values for factors corresponding to the source, the medium that would be transversed by a seismic wavelet, the target, and the receiving system, said factors including, source-to-receiver offset, radiated energy density, directivity, capture area, target reflection coefficient, divergence, and loss factor,

combining said values for said factors to produce a model amplitude spectrum of said seismic wavelet,

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by said seismic wavelet,

deriving the value of any phase contributions of load and receiver array impedances,

combining said components of said electromotive force and said load and receiver array impedances to produce a model phase spectrum of a seismic wavelet,

combining said model amplitude spectrum with said model phase spectrum to produce a model frequency spectrum for a model seismic wavelet for said source-to-receiver offset, and

deconvolving a seismic trace for said source-to-receiver offset by said model seismic wavelet.

39. An average-amplitude correction factor method of processing seismic data, which comprises

determining values for factors for a source-to-receiver offset in a frequency band, corresponding to the source, the medium that would be transversed by a seismic wavelet, and the receiving system, said factors including directivity, capture area, divergence, and loss factor,

combining said values for said factors to produce a first average amplitude for said source-to-receiver offset for said frequency band,

generating average amplitudes for each source-to-receiver offset in said frequency band,

calculating average amplitude correction factors as the ratios of said average amplitudes to said first average amplitude, and

multiplying seismic traces at said source-to-receiver offsets by said average amplitude correction factors at the respective offsets.

40. A zero phase filtering method of processing recorded seismic data, which comprises

determining an amplitude spectrum for a model seismic wavelet for a source-to-receiver offset corresponding to one in the recorded seismic data and frequency band,

generating an amplitude spectrum for each model seismic wavelet at each source-to-receiver offset corresponding to those in the recorded seismic data for said frequency band to determine amplitude spectra,

calculating the zero phase filters from the ratios of said amplitude spectra to said amplitude spectrum, and

multiplying the zero phase filters by seismic traces in said frequency band at respective source-to-receiver offsets.

41. A prestack deconvolution method of processing a model seismic trace, which comprises

determining values for factors corresponding to the source, the medium that would be transversed by a seismic wavelet, the target, and the receiving system, said factors including, source-to-receiver offset, radiated energy density, directivity, capture area, target reflection coefficient, divergence and loss factor,

combining said values for factors to produce a model amplitude spectrum of said seismic wavelet,

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by said seismic wavelet

deriving the value of any phase contributions of load and receiver array impedances,

combining said components of said electromotive force and said load and receiver array impedances to produce a model phase spectrum of a seismic wavelet,

combining said model amplitude spectrum with said model phase spectrum to produce a model frequency spectrum for a model seismic wavelet,

determining a time-reflection sequence developed from a parallel layered subsurface,

convolving said model seismic wavelet with said time reflection sequence to develop a model seismic trace for said source-to-receiver offset, and

deconvolving said model trace by said model seismic wavelet.

42. An average-amplitude correction factor method of processing a model seismic gather, which comprises

determining values for factors for a source-to-receiver offset in a frequency band, corresponding to the source, the medium that would be transversed by a seismic wavelet, and the receiving system, said factors including directivity, capture area, divergence, and loss factor,

combining said values for said factors to produce a first average amplitude for said source-to-receiver offset for said frequency band,

generating an average amplitude for each source-to-receiver offset in said frequency band,

calculating average amplitude correction factors as the ratios of said average amplitudes to said first average amplitude, and

multiplying the average amplitude correction factors by seismic traces at respective source-to-receiver offsets.

43. A zero phase filtering method of processing a model seismic gather, which comprises

determining an amplitude spectrum for a model seismic wavelet for a source-to-receiver offset and frequency band,

generating an amplitude spectrum for each model seismic wavelet at each source-to-receiver offset for said frequency band to determine amplitude spectra,

calculating zero phase filters from the ratios of said amplitude spectra to said amplitude spectrum, and

multiplying the zero phase filters by model traces in the frequency domain at respective source-to-receiver offsets.

44. A method creating a stacked modeled seismic wavelet that simultaneously incorporates therein a multiplicative effect of source-to-receiver factors which would affect a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

generating models of unprocessed seismic wavelets for source-to-receiver offsets, and

processing said models of unprocessed seismic wavelets at different source-to-receiver offsets into a model stacked wavelet.

45. A post stack deconvolution method of processing stacked seismic data, which comprises

generating models of unprocessed seismic wavelets for source-to-receiver offsets,

processing said models of unprocessed seismic wavelets at different source-to-receiver offsets into a model stacked wavelet, and

deconvolving stacked seismic data by said model stacked wavelet.

46. A method of deriving a seismic data gathering system frequency response required to produce requisite received electrical energy density of a seismic wavelet issued from a source, transverses a medium, is reflected from a target, and is received by a receiving system by utilizing the following seismic range equation:

##EQU27## having seven elements

     1) E(f) is the radiated energy density from a source at frequency, f;

2) D(θ

_s,φ

_s,f) is source directivity along the θ

_s, φ

_s direction;

3) A_c (θ

_H,φ

_H,f) is the capture area of a receiving system for incident angle θ

_H,φ

_H ;

4) R_T is the P-wave reflection coefficient of a target interface;

5) D_v is the divergence;

6) L(f) is representative of the losses associated with seismic data gathering; and

7) E_r (f) is the received energy density at a receiver array,

said method comprising

selecting a system requisite received electrical energy density of the seismic wavelet returned from subsurface,

determining physical subsurface characteristics, for subsurface layers (i) transversed by the seismic wavelet, including P-wave velocity (α

i), S-wave velocity (β

_i), density (ρ

_i), and thickness (h_i), assuming the seismic wavelet path begins at the source of a seismic data gathering system, at frequency (f), through the medium at ray angle (θ

s) with respect to the normal to the surface and at corresponding ray angles (θ

_i) through subsurface layers, to the predetermined target bed at depth (d) through said subsurface layers to a receiving system of the seismic data gathering system,

determining the target'"'"'s power reflection coefficient (R_T²),

calculating divergence (D_v) for a given offset,

calculating the loss factor (L(f)) associated with the subsurface layers, and

determining a system frequency response as a function of radiated energy density from the source, source directivity, and capture area from the product of received electrical energy density (E_r (f)), the divergence (D_v), and the loss factor divided by the square of the target'"'"'s power reflection coefficient.

47. A method in accordance with claim 46, wherein said target'"'"'s power reflection coefficient is derived from the said ray angle (θ

_i), said seismic velocity (α

_i,α

_i+1,β

_i and β

_i+1), and said density (ρ

_i and ρ

_i+1) at layers at the interface.

48. A method in accordance with claim 46, wherein said divergence is derived from said thickness (h_i) of the subsurface layer transversed by the seismic wavelet, said ray angle (θ

_i) in each subsurface layer, and offset distance X.

49. A method in accordance with claim 46, wherein said loss factor includes transmission loss (L_t).

50. A method in accordance with claim 49, wherein said transmission loss (L_t) is a loss associated with crossing the interfaces twice and is derived from transmission coefficients associated with the corresponding subsurface layers traversed (T_i'"'"'i+1 T_i+1'"'"'i).

51. A method in accordance with claim 50, wherein said interface include the following interfaces:

solid-to-solid, fluid-to-solid, and solid-to-fluid.

52. A method in accordance with claim 46, wherein said loss factor includes Q-loss (L_Q (f)).

53. A method in accordance with claim 52, wherein said Q-loss is derived from an attenuation constant (Q_i) for each transversed subsurface layer, said P-wave velocity (α

_i) of each transversed subsurface layer, said width of each transversed subsurface layer (h_i), said frequency (f), and said ray angle (θ

_i).

54. A method in accordance with claim 53, wherein said attenuation constant is estimated by finding an effective attenuation constant (Q) down to said target depth from existing seismic data in the area.

55. A method in accordance with claim 46, wherein said loss factor includes interbed multiple loss L_ib (f).

56. A method in accordance with claim 46, wherein said radiated energy density E(f) is derived from a number of source array element (N), said number being at least one, said frequency (f), said seismic velocity of first layer traversed (α

₁), said density of the first layer transversed (ρ

₁), and an illumination factor.

57. A method in accordance with claim 56, wherein said illumination factor (I_n (f)) is derived from an amplitude spectrum (A_n (f)) of the radiated seismic wavelet, a value of any firing delay (δ

_n), and said frequency (f).

58. A method in accordance with claim 46, wherein said source directivity is derived from the ratio of a radiated energy density per unit solid angle radiated in particular direction (θ

_s,φ

_s) to radiated energy density E(f).

59. A method in accordance with claim 46, wherein said capture area (A_c (θ

_H,φ

_H,f)) is determined from the multiplication of capture area along the acoustic axis and a transmitting pattern of a receiving system.

60. A method in accordance with claim 59, wherein said capture area along the acoustic axis, said axis being normal to the surface, is derived from receiving array sensitivity S_H (f), value of any load and receiving array impedances (Z_L (f) and Z_H (f), said density of the first transversed layer, said P-wave velocity of the first transversed layer, and array depth.

61. A method in accordance with claim 59, wherein said transmitting pattern is defined by the ratio of a receiving array directivity D(θ

_H,φ

_H,f) along the incident ray direction to the directivity of the receiving array along the acoustic axis (D(O,φ

_H,f), said axis being normal to the surface.

62. A method in accordance with claim 46, and including a method for deriving a seismic data gathering system source frequency response required to produce a requisite received electrical energy density of a seismic wavelet issued from a source, transverses a medium, is reflected from a target, and is received by a receiving system for specified receiver characteristics, said method comprising

specifying a receiving system including the value of any receiving array and load impedances (Z_H (f) and Z_L (f)), receiving array sensitivity (S_H (f)), and receiving array depth (d_H),

calculating said capture are (A_c (θ

_H,φ

_H,f)) from the product of the capture area along the acoustic axis and transmitting pattern of receiving array, and

dividing said system response by said capture area to determine the seismic data gathering system source frequency response as a function of source directivity and radiated energy density.

63. A method in accordance with claim 46, and including a method for deriving a seismic data gathering system receiver frequency response required to produce a requisite received electrical energy density of a seismic wavelet issued from a source, transverses a medium, is reflected from a target, and is received by a receiving system, for specified source characteristics, which comprises

specifying a source including a frequency spectrum of the outgoing waveforms from a number of individual source array elements, said number being at least one, a position of the source array elements when the number of said elements is greater than one, and a value of any firing delays associated with source array elements (δ

_n),

calculating said radiated energy density E(f),

calculating said source directivity from the ratio of said radiated energy density per unit solid angle radiated in a particular direction (θ

_s,φ

_s) to said radiated energy density E(f), and

dividing said system frequency response by said source directivity and said radiated energy density to determine the seismic data gathering system receiver frequency response.

64. A method of modeling an amplitude spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining values for the factors corresponding to the source, the medium, the target, and the receiving system that would affect the seismic wavelet, and

combining said values for said factors multiplicatively to produce a model amplitude spectrum of the seismic wavelet.

65. A method of modeling a frequency spectrum of a seismic wavelet that issues from a seismic source, traverses a medium, is reflected from a target, and is received by a receiving system, said method comprising

determining values for factors corresponding to the source, the medium, the target, and the receiving system that would affect a seismic wavelet,

combining said values for said factors multiplicatively to produce a model amplitude spectrum of the seismic wavelet,

determining phase components of an electromotive force (φ

.sub.ε

(f)) generated by the seismic wavelet,

deriving the value of any phase components of load and receiving array impedances,

combining said components of said electromotive force and said load and receiving array impedances to produce a model phase spectrum of the seismic wavelet, and

combining said model amplitude spectrum with said model phase spectrum to produce a model frequency spectrum of the seismic wavelet.

66. A method of interpreting stacked seismic traces derived from recorded seismic data, said method comprising

generating a model of an unprocessed seismic trace at a source-to-receiver offset corresponding to one in the recorded seismic data,

generating several models of unprocessed seismic traces for different source-to-receiver offsets corresponding to those in the recorded seismic data,

combining said models for said source-to-receiver offsets to develop an unprocessed model gather,

processing said unprocessed model gather into a stacked model trace, and

comparing variations in stacked seismic trace to variations in said stacked model trace.

67. A method of interpreting stacked seismic data derived from recorded seismic data wherein seismic data and modeled data are processed, stacked, and compared, said method comprising

generating a model of an unprocessed seismic trace for a source-to-receiver offset corresponding to one in the recorded seismic data,

generating a plurality of additional models of unprocessed seismic traces for different source-to-receiver offsets corresponding to those in the recorded seismic data,

combining said models to develop an unprocessed model gather,

processing said unprocessed model gather to produce a processed model gather,

processing the recorded seismic data to produce processed seismic data,

processing said processed model gather into a stacked model trace,

processing said processed seismic data into a stacked seismic trace, and

comparing said stacked seismic trace to said stacked model trace.

68. A method of interpreting stacked seismic data derived from recorded seismic data wherein seismic data and modeled data are stacked, processed, and compared at any step therein, said method comprising

generating a model of an unprocessed seismic trace for a source-to-receiver offset corresponding to one in the recorded seismic data,

generating a plurality of additional models of unprocessed seismic traces for different source-to-receiver offsets corresponding to those in the recorded seismic data,

combining said models to develop an unprocessed model gather,

processing said unprocessed model gather into an unprocessed stacked model trace,

processing the unprocessed recorded seismic data into an unprocessed stacked seismic trace,

processing said unprocessed model stacked trace to produce a processed model stacked trace,

processing said unprocessed stacked seismic data to produce model stacked data, and

comparing variations of said processed stacked seismic data to variations in said processed model stacked trace.

69. A method in accordance with claim 68 wherein said processing of both said unprocessed stacked model trace and unprocessed stacked seismic data incorporates a post stack deconvolution method, said method comprising

generating models of unprocessed seismic wavelets for source-to-receiver offsets corresponding to those recorded for the recorded seismic data,

processing said models of unprocessed seismic wavelets into a model stacked wavelet,

deconvolving said unprocessed model stacked trace by said model stacked wavelet, and

deconvolving said unprocessed stacked seismic data by said model stacked wavelet.