scholarly journals The cross-dip correction as a tool to improve imaging of crooked-line seismic data: a case study from the post-glacial Burträsk fault, Sweden

Solid Earth ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 581-598
Author(s):  
Ruth A. Beckel ◽  
Christopher Juhlin
Keyword(s):  
Seismic Data ◽  
Correction Term ◽  
Regional Scale ◽  
Synthetic Data ◽  
Shear Zones ◽  
Seismic Profile ◽  
Line Geometry ◽  
Processing Methods ◽  
Processing Scheme ◽  
The Cross

Abstract. Understanding the development of post-glacial faults and their associated seismic activity is crucial for risk assessment in Scandinavia. However, imaging these features and their geological environment is complicated due to special challenges of their hardrock setting, such as weak impedance contrasts, often high noise levels and crooked acquisition lines. A crooked-line geometry can cause time shifts that seriously de-focus and deform reflections containing a cross-dip component. Advanced processing methods like swath 3-D processing and 3-D pre-stack migration can, in principle, handle the crooked-line geometry but may fail when the noise level is too high. For these cases, the effects of reflector cross-dip can be compensated for by introducing a linear correction term into the standard processing flow. However, existing implementations of the cross-dip correction rely on a slant stack approach which can, for some geometries, lead to a duplication of reflections. Here, we present a module for the cross-dip correction that avoids the reflection duplication problem by shifting the reflections prior to stacking. Based on tests with synthetic data, we developed an iterative processing scheme where a sequence consisting of cross-dip correction, velocity analysis and dip-moveout (DMO) correction is repeated until the stacked image converges. Using our new module to reprocess a reflection seismic profile over the post-glacial Burträsk fault in northern Sweden increased the image quality significantly. Strike and dip information extracted from the cross-dip analysis helped to interpret a set of southeast-dipping reflections as shear zones belonging to the regional-scale Burträsk Shear Zone (BSZ), implying that the BSZ itself is not a vertical but a southeast-dipping feature. Our results demonstrate that the cross-dip correction is a highly useful alternative to more sophisticated processing methods for noisy datasets. This highlights the often underestimated potential of rather simple but noise-tolerant methods in processing hardrock seismic data.

scholarly journals The crossdip correction as a tool to improve imaging of crooked line seismic data: A case study from the post-glacial Burträsk fault, Sweden

2018 ◽  
Author(s):  
Ruth A. Beckel ◽  
Christopher Juhlin
Keyword(s):  
Seismic Data ◽  
Correction Term ◽  
Regional Scale ◽  
Synthetic Data ◽  
Shear Zones ◽  
Seismic Profile ◽  
Line Geometry ◽  
Processing Methods ◽  
Processing Scheme ◽  
Noise Tolerant

Abstract. Understanding the development of post-glacial faults and their associated seismic activity is crucial for risk assessment in Scandinavia. However, imaging these features and their geological environment is complicated due to special challenges of their hardrock setting, such as weak impedance contrasts, sometimes high noise levels and crooked acquisition lines. A crooked line geometry can cause time shifts that seriously de-focus and deform reflections containing a crossdip component. Advanced processing methods like swath 3D processing and 3D pre-stack migration can, in principle, handle the crooked line geometry, but may fail when the noise level is too high. For these cases, the effects of reflector crossdip can be compensated for by introducing a linear correction term into the standard processing flow. However, existing implementations of the crossdip correction rely on a slant stack approach which can, for some geometries, lead to a duplication of reflections. Here we present a module for the crossdip correction that avoids the reflection duplication problem by shifting the reflections prior to stacking. Based on tests with synthetic data, we developed an iterative processing scheme where a sequence consisting of crossdip correction, velocity analysis and DMO correction is repeated until the stacked image converges. Using our new module to reprocess a reflection seismic profile over the post-glacial Burträsk Fault in Northern Sweden increased the image quality significantly. Strike and dip information extracted from the crossdip analysis helped to interpret a set of southeast dipping reflections as shear zones belonging to the regional scale Burträsk Shear Zone (BSZ), implying that the BSZ itself is not a vertical, but a southeast dipping feature. Our results demonstrate that the crossdip correction is a highly useful alternative to more sophisticated processing methods for noisy datasets. This highlights the often underestimated potential of rather simple, but noise-tolerant methods, in processing hardrock seismic data.

One‐pass 3-D seismic extrapolation with the 45° wave equation

Geophysics ◽  
1997 ◽  
Vol 62 (6) ◽  
pp. 1817-1824 ◽  
Author(s):  
Hongbo Zhou ◽  
George A. McMechan
Keyword(s):  
Wave Equation ◽  
Seismic Data ◽  
Correction Term ◽  
Synthetic Data ◽  
Second Order ◽  
Order Partial Differential Equation ◽  
Third Order ◽  
Partial Differential ◽  
Numerical Tests ◽  
And Migration

One‐pass 3-D modeling and migration for poststack seismic data may be implemented by replacing the traditional 45° one‐way wave equation (a third‐order partial differential equation) with a pair of second‐ and first‐order partial differential equations. Except for an extra correction term, the resulting second‐order equation has a form similar to the Claerbout 15° one‐way wave equation, which is known to have a nearly circular impulse response. In this approach, there is no need to compensate for splitting errors. Numerical tests on synthetic data show that this algorithm has the desirable attributes of being second order in accuracy and economical to solve. A modification of the Crank‐Nicholson implementation maintains stability.

Seismic anisotropy and natural fractures from VSP and borehole sonic tools—A field study

Geophysics ◽  
1996 ◽  
Vol 61 (2) ◽  
pp. 456-466 ◽  
Author(s):  
Wallace E. Beckham
Keyword(s):  
Field Study ◽  
Shear Wave ◽  
Seismic Data ◽  
Seismic Anisotropy ◽  
Seismic Profile ◽  
Azimuthal Anisotropy ◽  
Small Scale ◽  
Natural Fractures ◽  
Vertical Seismic Profile ◽  
The Cross

A multicomponent vertical seismic profile (VSP), cross‐dipole shear‐wave log, formation micro imaging (FMI) log, and oriented core were obtained in the Brady Ranch 1–5 well, Carter County, Oklahoma in November 1992. The intent was to study the properties of fractured intervals and the response of the seismic data with respect to fracture orientation. The primary zones of interest were the Sycamore and Hunton carbonates. A full nine‐component VSP was obtained from 152 to 3010 m. Data from a cross‐dipole shear‐wave log were obtained primarily in the deep carbonates at 2600–2900 m. The VSP and cross‐dipole data gave estimates of the orientation of azimuthal anisotropy in the section, and indicate three changes in the orientation of azimuthal anisotropy with depth. An east‐northeast orientation was obtained in the deepest zone, which includes the carbonate interval. The cross‐dipole data indicate anisotropy having east‐northeast, east‐south‐east, and approximately north‐south orientations in this zone. The cross‐dipole tool may be responding to small scale microcracks, which may have more random orientations than the larger scale macrofractures. FMI log data and oriented core, also obtained in the deep carbonate section, indicate macrofractures oriented in east‐northeast and east‐southeast directions.

Tomography of diffraction-based focusing operators

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. R217-R225 ◽  
Author(s):  
Luiz Alberto Santos ◽  
Webe Joao Mansur ◽  
George A. McMechan
Keyword(s):  
Seismic Data ◽  
East Coast ◽  
Single Channel ◽  
Synthetic Data ◽  
Seismic Profile ◽  
The United States ◽  
Velocity Estimation ◽  
Velocity Analysis ◽  
Multichannel Data ◽  
Kinematic Information

Diffractions carry the same kinematic information provided by common focus point operators (CFPOs). Thus CFPO and diffraction time trajectories may be used separately, or combined into a single unified tomography for velocity analysis. Velocity estimation by tomography of CFPOs reduces the depth-velocity ambiguity compared to two-way time tomography. CFPO estimation is complicated where there are event discontinuities and diffractions. This problem is overcome by using the kinematic information in diffractions in near-offset common-offset gathers. The procedure is illustrated using synthetic data, and a single-channel field seismic profile from the Blake Ridge (off the east coast of the United States). The results show the effectiveness of the proposed method for estimation of velocity from single channel seismic data, and for refinement of the velocity field from multichannel data. Both applications are cost-competitive.

Regularization and datuming of seismic data by weighted, damped least squares

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. U67-U76 ◽  
Author(s):  
Robert J. Ferguson
Keyword(s):  
Least Squares ◽  
Seismic Data ◽  
Synthetic Data ◽  
Real Data ◽  
Structural Data ◽  
Irregular Sampling ◽  
Data Set ◽  
Near Surface ◽  
Damped Least Squares ◽  
Wavefield Extrapolation

The possibility of improving regularization/datuming of seismic data is investigated by treating wavefield extrapolation as an inversion problem. Weighted, damped least squares is then used to produce the regularized/datumed wavefield. Regularization/datuming is extremely costly because of computing the Hessian, so an efficient approximation is introduced. Approximation is achieved by computing a limited number of diagonals in the operators involved. Real and synthetic data examples demonstrate the utility of this approach. For synthetic data, regularization/datuming is demonstrated for large extrapolation distances using a highly irregular recording array. Without approximation, regularization/datuming returns a regularized wavefield with reduced operator artifacts when compared to a nonregularizing method such as generalized phase shift plus interpolation (PSPI). Approximate regularization/datuming returns a regularized wavefield for approximately two orders of magnitude less in cost; but it is dip limited, though in a controllable way, compared to the full method. The Foothills structural data set, a freely available data set from the Rocky Mountains of Canada, demonstrates application to real data. The data have highly irregular sampling along the shot coordinate, and they suffer from significant near-surface effects. Approximate regularization/datuming returns common receiver data that are superior in appearance compared to conventional datuming.

Restricted model domain time Radon transforms

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. A17-A21 ◽  
Author(s):  
Juan I. Sabbione ◽  
Mauricio D. Sacchi
Keyword(s):  
Inverse Problem ◽  
Seismic Data ◽  
Computational Cost ◽  
Synthetic Data ◽  
Model Space ◽  
Radon Transforms ◽  
Iterative Solver ◽  
Hard Thresholding ◽  
Restricted Model ◽  
Marine Data

The coefficients that synthesize seismic data via the hyperbolic Radon transform (HRT) are estimated by solving a linear-inverse problem. In the classical HRT, the computational cost of the inverse problem is proportional to the size of the data and the number of Radon coefficients. We have developed a strategy that significantly speeds up the implementation of time-domain HRTs. For this purpose, we have defined a restricted model space of coefficients applying hard thresholding to an initial low-resolution Radon gather. Then, an iterative solver that operated on the restricted model space was used to estimate the group of coefficients that synthesized the data. The method is illustrated with synthetic data and tested with a marine data example.

Stochastic inversion of pressure and saturation changes from time-lapse AVO data

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. C81-C92 ◽  
Author(s):  
Helene Hafslund Veire ◽  
Hilde Grude Borgos ◽  
Martin Landrø
Keyword(s):  
Stochastic Model ◽  
Seismic Data ◽  
Synthetic Data ◽  
Time Lapse ◽  
Bayesian Framework ◽  
Reservoir Modeling ◽  
Data Set ◽  
The North ◽  
Fluid Saturation ◽  
Likelihood Model

Effects of pressure and fluid saturation can have the same degree of impact on seismic amplitudes and differential traveltimes in the reservoir interval; thus, they are often inseparable by analysis of a single stacked seismic data set. In such cases, time-lapse AVO analysis offers an opportunity to discriminate between the two effects. We quantify the uncertainty in estimations to utilize information about pressure- and saturation-related changes in reservoir modeling and simulation. One way of analyzing uncertainties is to formulate the problem in a Bayesian framework. Here, the solution of the problem will be represented by a probability density function (PDF), providing estimations of uncertainties as well as direct estimations of the properties. A stochastic model for estimation of pressure and saturation changes from time-lapse seismic AVO data is investigated within a Bayesian framework. Well-known rock physical relationships are used to set up a prior stochastic model. PP reflection coefficient differences are used to establish a likelihood model for linking reservoir variables and time-lapse seismic data. The methodology incorporates correlation between different variables of the model as well as spatial dependencies for each of the variables. In addition, information about possible bottlenecks causing large uncertainties in the estimations can be identified through sensitivity analysis of the system. The method has been tested on 1D synthetic data and on field time-lapse seismic AVO data from the Gullfaks Field in the North Sea.

Application of complex-trace analysis to seismic data for random-noise suppression and temporal resolution improvement

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. V79-V86 ◽  
Author(s):  
Hakan Karsli ◽  
Derman Dondurur ◽  
Günay Çifçi
Keyword(s):  
Seismic Data ◽  
Trace Analysis ◽  
Noise Suppression ◽  
Single Channel ◽  
Random Noise ◽  
Synthetic Data ◽  
Low Frequency ◽  
Bright Spot ◽  
Phase Information ◽  
Resolution Improvement

Time-dependent amplitude and phase information of stacked seismic data are processed independently using complex trace analysis in order to facilitate interpretation by improving resolution and decreasing random noise. We represent seismic traces using their envelopes and instantaneous phases obtained by the Hilbert transform. The proposed method reduces the amplitudes of the low-frequency components of the envelope, while preserving the phase information. Several tests are performed in order to investigate the behavior of the present method for resolution improvement and noise suppression. Applications on both 1D and 2D synthetic data show that the method is capable of reducing the amplitudes and temporal widths of the side lobes of the input wavelets, and hence, the spectral bandwidth of the input seismic data is enhanced, resulting in an improvement in the signal-to-noise ratio. The bright-spot anomalies observed on the stacked sections become clearer because the output seismic traces have a simplified appearance allowing an easier data interpretation. We recommend applying this simple signal processing for signal enhancement prior to interpretation, especially for single channel and low-fold seismic data.

scholarly journals Appraising structural interpretations using seismic data — Theoretical elements

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. N29-N40
Author(s):  
Modeste Irakarama ◽  
Paul Cupillard ◽  
Guillaume Caumon ◽  
Paul Sava ◽  
Jonathan Edwards
Keyword(s):  
Seismic Data ◽  
Structural Model ◽  
Synthetic Data ◽  
Target Region ◽  
Structural Interpretation ◽  
Vertical Seismic Profiling ◽  
Seismic Image ◽  
Vsp Data ◽  
Phase Shift Data ◽  
Seismic Images

Structural interpretation of seismic images can be highly subjective, especially in complex geologic settings. A single seismic image will often support multiple geologically valid interpretations. However, it is usually difficult to determine which of those interpretations are more likely than others. We have referred to this problem as structural model appraisal. We have developed the use of misfit functions to rank and appraise multiple interpretations of a given seismic image. Given a set of possible interpretations, we compute synthetic data for each structural interpretation, and then we compare these synthetic data against observed seismic data; this allows us to assign a data-misfit value to each structural interpretation. Our aim is to find data-misfit functions that enable a ranking of interpretations. To do so, we formalize the problem of appraising structural interpretations using seismic data and we derive a set of conditions to be satisfied by the data-misfit function for a successful appraisal. We investigate vertical seismic profiling (VSP) and surface seismic configurations. An application of the proposed method to a realistic synthetic model shows promising results for appraising structural interpretations using VSP data, provided that the target region is well-illuminated. However, we find appraising structural interpretations using surface seismic data to be more challenging, mainly due to the difficulty of computing phase-shift data misfits.

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