Application of 2D Common Reflection Surface (CRS) Stack in Seismic Imaging

We present an extension of the Common Reflection Surface (CRS) stack that provides support for an arbitrary top surface topography. CRS stacking can be applied to the original prestack data without the need for any elevation statics. The CRS-stacked zero-offset section can be corrected (redatumed) to a given planar level by kinematic wave field attributes. The seismic processing results indicate that the CRS stacked section for rugged surface topography is better than the conventional stacked section for S/N ratio and better continuity of reflection events. Considering the multiple paths of zero-offset rays, the method deals with reflection information coming from different dips and performs the stack using the method of dip decomposition, which improves the kinematic and dynamic character of CRS stacked sections.

The success of standaxd seismic reflection imaging routines, such as Prestack Depth Migration or NMO/DMO/stack depends on the required macro-velocity model. Since their Kirchhoff type implementations collect all possible measured reflections events belonging to either a point in the time or in the depth domain they cannot account for the correct shape of the reflector. In contrast, a common-reflection surface (CRS) stack is a selective stack which depends only on the near-surface velocity. The CRS stack provides a new powerful approach to construct simulated zero-offset (ZO) sections from multicoverage reflection data. It accounts for arbitrary reflector shapes and enables us to establish the macro velocity model after the zero-offset simulation.

When the signal to noise ratio of seismic data is very low, velocity spectrum focusing will be poor., the velocity model obtained by conventional velocity analysis methods is not accurate enough, which results in inaccurate migration. For the low signal noise ratio (SNR) data, this paper proposes to use partial Common Reflection Surface (CRS) stack to build CRS gathers, making full use of all of the reflection information of the first Fresnel zone, and improves the signal to noise ratio of pre-stack gathers by increasing the number of folds. In consideration of the CRS parameters of the zero-offset rays emitted angle and normal wave front curvature radius are searched on zero offset profile, we use ellipse evolving stacking to improve the zero offset section quality, in order to improve the reliability of CRS parameters. After CRS gathers are obtained, we use principal component analysis (PCA) approach to do velocity analysis, which improves the noise immunity of velocity analysis. Models and actual data results demonstrate the effectiveness of this method.

This study introduces a Common Offset (CO) extension of the Common Reflection Surface (CRS) method to address seismic imaging challenges in complex geological settings and with noisy data. This CO-CRS approach aims to enhance the signal-to-noise ratio and overcome the limitations of conventional preconditioning techniques that rely on accurate parameterization. Building upon established work on zero-offset CRS (ZO-CRS), the CO method generates regularized prestack data suitable for both time- and depth-domain processing by interpolating missing offsets using a local hyperbolic approximation. Ultimately, this study utilizes CO-CRS for enhanced velocity analysis and data preconditioning prior to performing prestack time migration (PSTM). In this study, the CO-CRS is then used for velocity analysis and prestack time migration. The results show that prestack CO-CRS data yield improved time-migrated seismic images, and we suggest extending the application to the depth domain. To achieve a reliable velocity model for imaging, recursive seismic inversion (RSI) is applied to derive the velocity model using the PSTM stack and a velocity interval time, based on CRS semblance velocity analysis. Furthermore, the prestack depth migration (PSDM) is then tested. The depth-imaging results are reliable, and it can be concluded that combining the benefits of the CRS noise-reduction feature with more accurate velocity analysis and prestack migration can provide enhanced capabilities.

Common reflection surface (CRS) technology can be used in stack process to get simulated zero-offset section with higher S/N ratio than conventional method. However, poststack migration of CRS stacked data is not always satisfying due to serious suppression of diffraction wave and enhancement of reflection wave. Using kinematic parameters, Time migration result can be obtained directly from pre-stack data by extended CRS method. The so called “CRS prestack time migration” here is independent of macro velocity model as well as CRS stack. Meanwhile, property of high S/N ratio can be still preserved in migration section as stack section. Test results on synthetic data by this new approach show its promising application.

The main goal of 3D CRS (Common Reflection Surface) stack is the improvement of the image with respect to NMO/DMO processing route. However, also the set of parameters defining the CRS stacking surface are a precious source of information on subsurface properties. In 3D, the CRS second order traveltime trajectory is defined by eight parameters, that can be divided into three groups: KN, KNIP (each one is a 2x2 matrix with three independent parameters) and angles (azimuth and emergence). KN are mainly related to the subsurface reflectors geometry, KNIP to velocity; angles describe the normal ray emergence. The NIP-wave tomography method described in Duvenek, 2004 uses KNIP and angles to reconstruct a smooth velocity model in depth, suited for a PSDM and/or for petrophysical studies . In this paper, the first application to a real 3D data-set (from West Africa) of the method is presented. The comparison among common image gathers obtained from a reference velocity model and the ones coming out using NIP-wave tomography shows that a reliable velocity model can be reconstructed in a very cost-effective way directly from CRS processing.

As recent case studies demonstrated, the Common-Reflection-Surface (CRS) stack produces reliable stack sections with high resolution and superior signal-to-noise ratio compared to conventional stacking methods. Particularly for land data, the <br>increased computational expense required by the generalized high-density velocity analysis preceding the CRS stacking process often proves to be worthwhile. <br>In order to define optimal spatial stacking operators, the CRS stack extracts for every sample of the zero-offset section an entire set of physically interpretable stacking parameters. These so-called kinematic wavefield attributes, can be applied to solve various dynamic and kinematic stacking, modeling, and inversion problems. By this means, a very flexible CRS-stack-based seismic reflection imaging workflow can be established. The main steps of this workflow are, besides the CRS stack itself, residual static correction,determination of a macrovelocity model via tomographic inversion, and limited aperture Kirchhoff migration. The presented extension of the CRS-stack-based imaging workflow supports arbitrary top-surface topography. Both CRS stack and also CRS-stack-based residual static correction are applied to the original prestack data without the need of any elevation statics. Finally, a redatuming procedure relates the CRS-stacked zero-offset section, the kinematic wavefield attribute sections, and the quality control sections to a chosen planar measurement level.

We present a method to obtain a true-amplitude<br>migration and amplitude-versus-angle (AVA) at selected<br>points using the attributes generated by the<br>Common Reflection Surface (CRS) Stack. Our approach<br>combines the CRS stack/inversion process<br>applied to multicoverage data, together with the<br>use of a kinematic Kirchhoff migration, to achieve<br>true-amplitudes (TA) at assigned depth points of<br>the migrated images. The proposed method consists<br>of the following steps: (i) apply the CRS process<br>to the given multicoverage data; the obtained<br>CRS attributes are next used to produce a simple<br>macro-velocity depth model; (ii) perform an unweighted<br>Kirchhoff migration for imaging purposes<br>only; for selected points on target reflectors in the<br>migrated image, we use the macro-velocity model<br>to determine, by ray tracing, common-reflectionpoint<br>(CRP) gathers that belong to the input data;<br>for these rays, we compute the incident angles and<br>the geometrical spreadings; (iii) go back to CRP<br>gathers and compensate the amplitudes for geometrical<br>spreading. The results permit to construct<br>AVA curves on the assigned CRPs. In summary,<br>our method is designed to aggregate amplitude information<br>on selected points of a reflector, after a<br>purely kinematic image (migration) has been obtained.<br>The method is tested on a synthetic inhomogeneous<br>layered model with good results.

The Common Reflection Surface (CRS) method, introduced by Peter Hubral in 1997, is an alternative technique to the conventional CMP stacking. The CRS stack is able to provide not only improved simulated zero-offset sections, but also a set of parameters that convey more information of the propagating medium than the single NMO-velocity parameter of the classical CMP method. The objective of this work is to analyze the potential of the CRS method to produce seismic velocity models, analogously to the computation of the NMO velocities in the CMP method. We review the CMP and CRS methods, and compare their performances on illustrative synthetic and real data examples.

The Common Focal Point (CFP) method and the Common Reflection Surface (CRS) stack method are compared. The CRS method is a fast, highly automated procedure that provides high S/N ratio Migration to Zero Offset (MZO) images, by combining per image-point the reflection energy of a tangent are segment to the reflector.

Velocity model determination during seismic data processing is crucial for any kind of depth imaging. Tomography procedures are often used to generate suitable models. In this paper, we compare two approaches of grid tomography: prestack stereotomography (PST) and NIP‐wave tomography (NIPT). Whereas NIPT is based on Common Reflection Surface (CRS) stack attributes, and thus on the underlying hyperbolic second‐order traveltime approximation PST describes traveltimes by local slopes (i.e. linearly) in the prestack data domain. To analyze the impact of the different traveltime approximations on velocity model building we have applied both techniques to a real marine dataset. The obtained velocity models reveal that the reconstruction of high velocity contrasts by grid tomographic methods is limited due to the smooth description of the velocity distribution for the data set used in this study. The lateral resolution of velocities obtained from PST appears to be slightly better than those from NIPT which might be related to the difference in the local approximation of traveltimes and to the determination of input data. Other differences are mainly caused by different implementations of the inversion schemes, the different grid spacing and outliers in the input data. Careful pre‐processing of the data will therefore improve the model building as well as the depth imaging in both cases.

I used the common-reflection-surface (CRS) stack technique together with conventional common-midpoint processing and prestack depth migration (PSDM) to process three parallel high-resolution seismic reflection lines acquired in a closed industrial plant. This brownfield site, now undergoing remediation, is located within the Bagnoli district of the city of Naples, Italy, near the southeastern border of Campi Flegrei caldera. Compared with the other results, the CRS stack, followed by poststack depth migration, produced a seismic image more consistent with the expected subsurface structures and with outcropping units present in the area. The survey confirmed the presence under the brownfield site of some buried steps of Coroglio Fault, a main structure formed approximately [Formula: see text] ago, during the Neapolitan Yellow Tuff supereruption. Results have important implications for hazard assessment and geothermal exploration because the imaged faults certainly are preferential passageways for geothermal fluids and washed pollutants. These tests revealed that the common-reflection-surface stack can be a fast and cost-effective alternative to PSDM in settings in which structural complexity and high levels of ambient noise make it challenging to obtain a reliable background velocity model; therefore, allowing high-resolution reflection seismology to be successfully used in those environments.

Seismic and well-logging data are useful for comparison and then integratation for a comprehensive geophysical interpretation. In the course of this work, seismic results were compared with well-logging geophysical data and profiles for more reliable evaluation of groundwater formations in the Tokaj region, north-east Hungary. The seismic results and profiles were obtained by the Common Reflection Surface (CRS) stacking technique. This is an advantageous stacking technique that is expected to greatly improve seismic profiles. In connection with this, we also examined some well-logging geophysical profiles so that we can improve later results. By comparing and examining the two types of sections together, we provide a basis for various method developments that improve the sections. Thus, the aim is to fill in the missing data, so that the well-logging and seismic sections can be examined together as accurately as possible in order to gain a more accurate picture of the subsurface formations. It is important to determine the lithology and petrophysical characteristics using well logs. The section replacement the improvement of the units is done using machine learning-based and inversion methods such as factor analysis or cluster analysis. An important outcome in the application of geophysical inversion methods is that the results of different methods can be jointly interpreted and this can significantly increase the reliability of the results. The application of these methods and their development is expected to reduce uncertainty and ambiguity and to increase the accuracy of the sections.

In this paper we present the results of partial stacking of prestack seismic reflection data based on the kinematic wavefield attributes computed during the automatic CRS stack. The resulting CRS supergathers are more regularised and have better signal to noise ratio compared to original CMP gathers. The improved data can be used in any conventional processing tool instead of the original data, providing enhanced images of better quality. The CRS supergather method is especially suited for low fold seismic reflection data. Application of the new method to synthetic and real low fold data shows a clear improvement of seismograms as well as time and depth‐migrated sections.

The common-reflection-surface (CRS) stacking method produces stacked zero-offset (ZO) sections with a high signal-to-noise ratio, a good definition of the lateral continuity of seismic reflections as well as of reflections with steep dips. The stacking operator of the CRS method depends on three kinematic attributes that are determined through optimization algorithms from the prestack data. In spite of the good results obtained so far with this method, there are still problems to be bypassed, such as the correct simulation of events with conflicting dips and diffraction events. In this work we present one application of the CRS stacking operator in the prestack time migration, i.e., instead of simulating a ZO stacked section, the result is a time migrated section. To demonstrate the efficiency and robustness, we apply this new prestack time migration approach based on CRS method in a synthetic and real land dataset.