Estimation of long‐wavelength near‐surface velocity and low‐relief structural anomalies Part I. A case history in central Saudi Arabia

1997 ◽  
Author(s):  
Peter I. Pecholcs ◽  
Sun Nguyen ◽  
Dan Kosloff ◽  
Alex Litvin
Keyword(s):  
Saudi Arabia ◽  
Case History ◽  
Surface Velocity ◽  
Near Surface ◽  
Long Wavelength ◽  
Structural Anomalies

LONG WAVELENGTH STATIC ESTIMATION

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 939-959 ◽  
Author(s):  
Aaron H. Booker ◽  
A. Frank Linville ◽  
Cameron B. Wason
Keyword(s):  
Surface Effects ◽  
Mackenzie Delta ◽  
Model Data ◽  
Static Structure ◽  
Near Surface ◽  
Long Wavelength ◽  
Time Profiles ◽  
Common Depth Point ◽  
Theoretical Performance ◽  
Structural Anomalies

Estimation and removal of near‐surface effects in common‐depth‐point (CDP) data have been frequently discussed in the literature. A common problem with many automated statics techniques is their inability to extract statics whose spatial wavelengths are longer than a spread length. This, of course, can result in false structural anomalies. This paper describes an approach which extends the useful static estimation bandwidth to wavelengths of the order of 4 to 8 spread lengths. Traveltimes from one or more reflecting horizons are picked at each depth point and CDP offset. The time profiles are then decomposed into source static, receiver static, structure, and residual normal moveout (RNMO) estimates, and the process is iterated if required. A suite of analytical displays provides the user with direct QC measures of the traveltime picking performance. The technique will be demonstrated on model data to illustrate the theoretical performance over slowly changing near‐surface weathering anomalies. In addition, field examples will be shown from the Mackenzie Delta where permafrost variability in the near‐surface can create large traveltime anomalies.

Data-driven tomographic velocity analysis in tilted transversely isotropic media: A 3D case history from the Canadian Foothills

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. VE261-VE268 ◽  
Author(s):  
Sylvestre Charles ◽  
David R. Mitchell ◽  
Rob A. Holt ◽  
Jiwu Lin ◽  
John Mathewson
Keyword(s):  
Case History ◽  
Model Building ◽  
Velocity Model ◽  
Data Driven ◽  
Surface Velocity ◽  
Near Surface ◽  
Model Driven ◽  
Velocity Model Building ◽  
Data Driven Approach ◽  
Anisotropy Model

We evaluated how velocity and anisotropy model-building strategies affect seismic imaging in the Canadian Foothills Thrust Belt by comparing the results of a model-driven approach with those of a data-driven approach. Two independently run Kirchhoff prestack depth-imaging projects were initiated using different static corrections for near-surface weathering layers and using different velocity and anisotropy model-building strategies. We observed that an isotropic data-driven reflection tomography velocity model-building approach resulted in a significantly better stack image than did a highly interpretive anisotropic model-driven velocity model-building approach. By carefully introducing anisotropy into the former, data-driven approach, we achieved significant improvements in positioning, including more accurate depth ties between the seismic image and well tops and better definition of structural geometries. The differences in the imaging observed at the various stages of this case history illustrate the sensitivity of the final depth images to the treatment of the near-surface velocity field, the macrointerval velocity model-building technique, and the choices of [Formula: see text] and [Formula: see text], which are the Thomsen anisotropy parameters for tilted transverse isotropy. The data-driven approach successfully challenged the historical idea that we must perform a geologic interpretation of the seismic data to derive an accurate depth velocity model in a complex geologic setting.

Near-surface and anisotropy modeling for efficient land seismic depth imaging in low-relief geology

2017 ◽  
Vol 5 (4) ◽  
pp. SR1-SR12 ◽  
Author(s):  
Daniele Colombo ◽  
Ernesto Sandoval-Curiel ◽  
Mats Ris ◽  
Salvarajah Seeni
Keyword(s):  
Joint Inversion ◽  
Surface Velocity ◽  
Accurate Estimation ◽  
Earth Model ◽  
Velocity Analysis ◽  
Near Surface ◽  
Depth Imaging ◽  
Long Wavelength ◽  
Transient Electromagnetic ◽  
Seismic Image

Prestack depth migration of land data presents unique characteristics and challenges that distinguish it from the workflows applied for marine data. Such unique characteristics are primarily related to the near surface. In areas of low-relief geology, near-surface velocity variations can obscure the reservoir structure. The remaining deeper earth model section has good lateral continuity and can be described effectively by smooth velocity fields. Strategies for estimating the near-surface effects and incorporating them into a processing workflow are of primary importance for the successful depth imaging of land seismic data. The second important aspect of a depth imaging workflow is that the seismic image must honor the well markers or formation tops. The subhorizontal fine-scale layering of low-relief structures can cause anisotropy that needs to be taken into account to achieve accurate well ties and good image quality. We have evaluated the application of an efficient workflow to achieve fast and reliable depth imaging in layered geology; this involves the decomposition of the near-surface velocity into short-, medium-, and long-wavelength terms followed by reflection velocity analysis and anisotropic parameter scanning. The long-wavelength components are solved by dynamic velocity analysis, whereas the medium- and short-wavelength terms are evaluated by surface-consistent analysis applied to refracted and reflected data. Interaction with seismic interpreters and geology-consistent updates mitigates the possibility of introducing errors in areas not covered by wells. The workflow is applied to a structure-controlled wadi in central Saudi Arabia showing complex near-surface conditions and imaging problems. The study incorporates high-resolution helicopter-borne transient electromagnetic data that are used to constrain seismic traveltime inversion through cross-gradient structural regularization (joint inversion). Fast and robust depth imaging constrained by well data is obtained through accurate estimation of near-surface velocities, anisotropy, and geology-consistent analysis.

scholarly journals Physics-Based Relationship for Pore Pressure and Vertical Stress Monitoring Using Seismic Velocity Variations

2021 ◽  
Vol 13 (14) ◽  
pp. 2684
Author(s):  
Eldert Fokker ◽  
Elmer Ruigrok ◽  
Rhys Hawkins ◽  
Jeannot Trampert
Keyword(s):  
Pore Pressure ◽  
Seismic Velocity ◽  
Pressure Head ◽  
Groundwater Table ◽  
Surface Velocity ◽  
Seismic Velocities ◽  
Stress Monitoring ◽  
Near Surface ◽  
Velocity Variations ◽  
Velocity Changes

Previous studies examining the relationship between the groundwater table and seismic velocities have been guided by empirical relationships only. Here, we develop a physics-based model relating fluctuations in groundwater table and pore pressure with seismic velocity variations through changes in effective stress. This model justifies the use of seismic velocity variations for monitoring of the pore pressure. Using a subset of the Groningen seismic network, near-surface velocity changes are estimated over a four-year period, using passive image interferometry. The same velocity changes are predicted by applying the newly derived theory to pressure-head recordings. It is demonstrated that the theory provides a close match of the observed seismic velocity changes.

Surface-Wave Simulation for the Continuously Moving Seismic Sources

2021 ◽  
Author(s):  
Yuefeng Yan ◽  
Chengyu Sun ◽  
Tengfei Lin ◽  
Jiao Wang ◽  
Jidong Yang ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Velocity Estimation ◽  
Surface Velocity ◽  
Seismic Sources ◽  
Near Surface ◽  
Moving Source ◽  
Source Data ◽  
Doppler Effects

Abstract In exploration and earthquake seismology, most sources used in subsurface structure imaging and rock property estimation are fixed in certain positions. Continuously moving seismic sources, such as vehicles and the metro, are one kind of important passive sources in ambient noise research. Commonly, seismic data acquisition and processing for moving sources are based on the assumption of simple point passive sources, and the dispersion curve inversion is applied to constrain near-surface velocity. This workflow neglects the Doppler effects. Considering the continuously moving properties of the sources, we first derive the analytical solution for the Rayleigh waves excited by heavy vehicles and then analyze their Doppler effects and dispersion curves. We observe that the moving source data have the Doppler effect when compared with the changes in the frequency of the source intensity, but this effect does not affect the frequency dispersion of Rayleigh waves. The dispersion curves computed for moving source records are consistent with the analytical dispersion solutions, which provide a theoretical foundation for velocity estimation using moving source data.

AN APPROACH TO INVERSE FILTERING OF NEAR‐SURFACE LAYER EFFECTS FROM SEISMIC RECORDS

Geophysics ◽  
1961 ◽  
Vol 26 (6) ◽  
pp. 754-760 ◽  
Author(s):  
Pierre L. Goupillaud
Keyword(s):  
Surface Layer ◽  
Seismic Reflection ◽  
Normal Incidence ◽  
Resolving Power ◽  
Surface Velocity ◽  
Inverse Filtering ◽  
Near Surface ◽  
Seismic Records ◽  
Stratification Variable ◽  
Velocity Information

This paper suggests a scheme for compensating the effects that the near‐surface stratification, variable from spread to spread, produces on both the character and the timing of the seismic traces. For this purpose, accurate near‐surface velocity information is mandatory. This scheme should greatly reduce the correlation difficulties so frequently encountered in many areas. It may also be used to enhance the resolving power of the seismic reflection technique. The approach presented here is based on the rather restrictive assumptions of normal incidence, parallel equispaced plant reflectors, and noiseless conditions.

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