摘要:

AbstractMuch of the success of modern seismic data processing derives from the use of the stacking process. Unfortunately, as is well known, conventional normal moveout correction (NMO) introduces mispositioning of data, and hence mis‐stacking, when dip is present. Dip moveout correction (DMO) is a technique that converts non‐zero‐offset seismic data after NMO to true zero‐offset locations and reflection times, irrespective of dip. The combination of NMO and DMO followed by post‐stack time migration is equivalent to, but can be implemented much more efficiently than, full time migration before stack.In this paper we consider the frequency‐wavenumber DMO algorithm developed by Hale. Our analysis centres on the result that, for a given dip, the combination of NMO at migration velocity and DMO is equivalent to NMO at the appropriate, dip‐dependent, stacking velocity. This perspective on DMO leads to computationally efficient methods for applying Hale DMO and also provides interesting insights on the nature of both DMO and conventi

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01843.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFirst breaks of 2D deep reflection data were used to construct velocity‐depth models for improved static corrections to a deeper datum level and for geological interpretations. The highly redundant traveltime data were automatically picked and transformed directly into a velocity‐depth model by maximum depth methods such as the Giese‐ and the Slichter‐method. Comparisons with the results of synthetic calculations and a tomographic approach using iterative inversion methods (ART, SIRT) showed that maximum depth methods provide reliable velocity models as a basis for the computation of static corrections. These methods can economically be applied during data acquisition in the field. They provide particularly long‐period static anomalies, which are of the order of 20–40 ms (0.5‐1 wavelength) within CMP gathers of an example of a deep reflection profile in SW‐Germany sited on crystalline basement. Reprocessing of this profile, which was aimed at the comparison between the effects of the originally used and the new statics, did not result in dramatically improved stacking quality but showed a subtle influence on the detailed appearance of deep

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01844.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractConverted waves require special data processing as the wave paths are asymmetrical. The CMP concept is not applicable for converted PS waves, instead a sorting algorithm for a common conversion point (CCP) has to be applied. The coordinates of the conversion points in a single homogeneous layer can be calculated as a function of the offset, the reflector depth and the velocity ratiovP/ vs.For multilayered media, an approximation for the coordinates of the conversion points can be made.Numerical tests show that the traveltime of PS reflections can be approximated with sufficient accuracy for a certain offset range by a two‐term series truncation. Therefore NMO corrections can be calculated by standard routines which use the hyperbolic approximation of the reflection traveltime curves.The CCP‐stacking technique has been applied to field data which have been generated by three vertical vibrators. The in‐line horizontal components have been recorded. The static corrections have been estimated from additional P‐ and SH‐wave measurements for the source and geophone locations, respectively. The data quality has been improved by processes such as spectral balancing.A comparison with the stacked results of the corresponding P‐ and SH‐wavefield surveys shows a good coherency of structural features in P‐, SH‐ and

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01845.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFrequency‐domain methods are well suited to the imaging of wide‐aperture cross‐hole data. However, although the combination of the frequency domain with the wavenumber domain has facilitated the development of rapid algorithms, such as diffraction tomography, this has also required linearization with respect to homogeneous reference media. This restriction, and association restrictions on source‐receiver geometries, are overcome by applying inverse techniques that operate in the frequency‐space domain.In order to incorporate the rigorous modelling technique of finite differences into the inverse procedure a nonlinear approach is used. To reduce computational costs the method of finite differences is applied directly to the frequency‐domain wave equation. The use of high speed, high capacity vector computers allow the resultant finite‐difference equations to be factored in‐place. In this way wavefields can be computed for additional source positions at minimal extra cost, allowing inversions to be generated using data from a very large number of source positions.Synthetic studies show that where weak scatter approximations are valid, diffraction tomography performs slightly better than a single iteration of non‐linear inversion. However, if the background velocities increase systematically with depth, diffraction tomography is ineffective whereas non‐linear inversion yields useful images from one frequency component of the data after a single iteration. Further synthetic studies indicate the efficacy of the method in the time‐lapse monitoring of injection fluids in tertiary hydrocar

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01846.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIt is advantageous to consider inversion of multi‐source (wide‐aperture) cross‐hole data using methods that (i) are based on the wave equation rather than its high‐frequency ray approximation, and (ii) use the full information content of the recorded wavefield rather than only first‐arrival times. Wave‐theoretical methods require the ability to forward‐model appropriate wave equations for all source positions in arbitrary reference media. This can be achieved using a frequency‐domain elastic wave propagator that facilitates the modelling of multi‐source data at the cost of temporal bandwidth. The trade‐off is deliberate; the propagator is applied to the cross‐hole imaging problem, in which wide spatial bandwidths are more important than temporal bandwidth.By using the frequency‐domain propagator, non‐linear inverse techniques are applied to data from a very large number of source positions. The method can be applied in 2D media of arbitrarya prioricomplexity. In a synthetic example, compressional and shear‐velocity perturbations are successfully resolved with one iteration using only a single frequency component of wide‐aperture

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01847.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01848.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1990.tb01849.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY