Determination of wavefront attributes by differential evolution in the presence of conflicting dips

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. V229-V239 ◽  
Author(s):  
Jan Walda ◽  
Dirk Gajewski
Keyword(s):  
Differential Evolution ◽  
Model Building ◽  
Optimization Technique ◽  
Velocity Model ◽  
Search Space ◽  
Global Maximum ◽  
Local Maxima ◽  
Parameter Search ◽  
Common Reflection Surface ◽  
And Migration

The common-reflection surface (CRS) method represents a multidimensional stacking approach; i.e., the stacking surface is determined in the midpoint and offset directions. In the 2D case, three attributes span the stacking surface, thus requiring a three-parameter search contrary to a one-parameter search in the classic common-midpoint stack. However, CRS wavefront attributes use data redundancy in the midpoint direction as well, which makes them very useful in several seismic applications, e.g., data preconditioning, velocity model building, and migration. Contrary to previous works, we simultaneously estimate CRS attributes using differential evolution in subcubes of the 3D search space. Differential evolution is a global optimization technique that performs particularly well when the objective function is unknown. Because we apply DE for each subcube, we could find local maxima, additionally to the global maximum. Therefore, conflicting dips are recognized and can be used for the stack and subsequent CRS attribute-based processing, which has been an issue in the past. Our land data results from the Donbas Foldbelt in southeast Ukraine demonstrate that our method reduces coherent steep dipping noise and reveal more subsurface structures. Application of the CRS attributes for prestack data enhancement shows that velocity analysis can be carried out more reliably.

Velocity-estimation improvements and migration/demigration using the common-reflection surface with continuing deconvolution in the time domain

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. S229-S238 ◽  
Author(s):  
Martina Glöckner ◽  
Sergius Dell ◽  
Benjamin Schwarz ◽  
Claudia Vanelle ◽  
Dirk Gajewski
Keyword(s):  
Model Building ◽  
Velocity Model ◽  
Velocity Estimation ◽  
Initial Time ◽  
Model Errors ◽  
Imaging Methods ◽  
Time Migration ◽  
Common Reflection Surface ◽  
The Common ◽  
And Migration

To obtain an image of the earth’s subsurface, time-imaging methods can be applied because they are reasonably fast, are less sensitive to velocity model errors than depth-imaging methods, and are usually easy to parallelize. A powerful tool for time imaging consists of a series of prestack time migrations and demigrations. We have applied multiparameter stacking techniques to obtain an initial time-migration velocity model. The velocity model building proposed here is based on the kinematic wavefield attributes of the common-reflection surface (CRS) method. A subsequent refinement of the velocities uses a coherence filter that is based on a predetermined threshold, followed by an interpolation and smoothing. Then, we perform a migration deconvolution to obtain the final time-migrated image. The migration deconvolution consists of one iteration of least-squares migration with an estimated Hessian. We estimate the Hessian by nonstationary matching filters, i.e., in a data-driven fashion. The model building uses the framework of the CRS, and the migration deconvolution is fully automated. Therefore, minimal user interaction is required to carry out the velocity model refinement and the image update. We apply the velocity refinement and migration deconvolution approaches to complex synthetic and field data.

scholarly journals A study of sub-basalt depth imaging using the local Radon attributes on the Erlend Tertiary volcanic complex - North of Shetland, UK

2008 ◽  
Vol 87 (2) ◽  
pp. 135-149
Author(s):  
A. Droujinine ◽  
J. Pajchel ◽  
K. Hitchen
Keyword(s):  
Model Building ◽  
Region Of Interest ◽  
Thick Layer ◽  
Velocity Model ◽  
Volcanic Complex ◽  
Depth Imaging ◽  
The North ◽  
Discrete Radon Transform ◽  
Imaging Results ◽  
And Migration

AbstractAcquiring conventional 3 km towed streamer data along a 2D profile in the North of Shetland (UK) enables us to use the local Radon-attributes within the context of depth processing methodology for accurate delineation of volcanic units and imaging beneath high-velocity layers. The objective is to map the radially-dipping structure of the Erlend pluton and to investigate the potential existence of relatively soft Cretaceous sediments underneath volcanic units. Success in the Erlend Volcano study requires strict attention to the separation between different groups of events. The crucial point is the generalized discrete Radon transform formulated in terms of local wavefront (dip and curvature) characteristics. This transform is utilized during pre-CMP processing and migration to minimize event-coupling artefacts. These artefacts represent cross-talk energy between various wave modes and include the unwanted part of the wavefield. We show how to produce detailed subsurface images within the region of interest (exploration prospect only) by applying the closely tied processes of prestack event enhancement and separation, well-driven time processing for velocity model building, and final event-based prestack depth imaging. Results show enhanced structural detail and good continuity of principal volcanic units and deeper reflections, suggesting a faulted 0.6 – 0.9 km thick layer of Cretaceous sediments in the proximity of well 209/09-1. Our interpretation complements existing low-resolution geophysical models inferred from gravity and wide-angle seismic data alone.

A Novel Mutation Strategy for Differential Evolution

2016 ◽  
pp. 20-31 ◽  
Author(s):  
Hira Zaheer ◽  
Millie Pant ◽  
Sushil Kumar ◽  
Oleg Monakhov
Keyword(s):  
Differential Evolution ◽  
Novel Mutation ◽  
Optimization Technique ◽  
Search Space ◽  
Additional Parameter ◽  
Solution Vector ◽  
Mutation Strategy ◽  
Suggested Strategy ◽  
The Difference ◽  
Mutation Strategies

Differential Evolution (DE) has attained the reputation of a powerful optimization technique that can be used for solving a wide range of problems. In DE, mutation is the most important operator as it helps in generating a new solution vector. In this paper we propose an additional mutation strategy for DE. The suggested strategy is named DE/rand-best/2. It makes use of an additional parameter called guiding force parameter K, which takes a value between (0,1) besides using the scaling factor F, which has a fixed value. De/rand-best/2 makes use of two difference vectors, where the difference is taken from the best solution vector. One vector difference will be produced with a randomly generated mutation factor K (0,1). It will add a different vector to the old one and search space will increase with a random factor. Result shows that this strategy performs well in comparison to other mutation strategies of DE.

scholarly journals A Differential Evolution Based MPPT Method for Photovoltaic Modules under Partial Shading Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Kok Soon Tey ◽  
Saad Mekhilef ◽  
Hong-Tzer Yang ◽  
Ming-Kai Chuang
Keyword(s):  
Differential Evolution ◽  
Characteristic Curve ◽  
Intensity Variation ◽  
Search Space ◽  
Maximum Power ◽  
Global Maximum ◽  
Pv System ◽  
Maximum Power Point ◽  
Partial Shading ◽  
Power Point

Partially shaded photovoltaic (PV) modules have multiple peaks in the power-voltage(P-V)characteristic curve and conventional maximum power point tracking (MPPT) algorithm, such as perturbation and observation (P&O), which is unable to track the global maximum power point (GMPP) accurately due to its localized search space. Therefore, this paper proposes a differential evolution (DE) based optimization algorithm to provide the globalized search space to track the GMPP. The direction of mutation in the DE algorithm is modified to ensure that the mutation always converges to the best solution among all the particles in the generation. This helps to provide the rapid convergence of the algorithm. Simulation of the proposed PV system is carried out in PSIM and the results are compared to P&O algorithm. In the hardware implementation, a high step-up DC-DC converter is employed to verify the proposed algorithm experimentally on partial shading conditions, load variation, and solar intensity variation. The experimental results show that the proposed algorithm is able to converge to the GMPP within 1.2 seconds with higher efficiency than P&O.

Generalized staining algorithm for seismic modeling and migration

Geophysics ◽  
2017 ◽  
Vol 82 (1) ◽  
pp. T17-T26 ◽  
Author(s):  
Qihua Li ◽  
Xiaofeng Jia
Keyword(s):  
Model Building ◽  
Signal To Noise Ratio ◽  
Velocity Model ◽  
Seismic Modeling ◽  
Target Region ◽  
The Real ◽  
Subsurface Structures ◽  
Velocity Model Building ◽  
And Migration ◽  
Amplitude Preservation

The staining algorithm is introduced to improve the signal-to-noise ratio (S/N) of poorly illuminated subsurface structures in seismic imaging. However, the amplitudes of the original and the stained wavefield, i.e., the real and the imaginary wavefields, differ by several orders of magnitude, and the waveform of the stained wavefield may be greatly distorted. We have developed a generalized staining algorithm (GSA) to achieve amplitude preservation in the stained wavefield. The real wavefield and the stained wavefield propagate in the same velocity model. A source wavelet is used as the source of the real wavefield; however, the real wavefield is extracted from the stained area as the source of the stained wavefield. The GSA maintains some properties of the original staining algorithm. The stained wavefield is synchronized with the real wavefield, and it contains only information relevant to the target region. By imaging with the stained wavefield, we obtain higher S/Ns in images of target structures. The most significant advantage of our method is the amplitude preservation of the stained wavefield, which means that this method could potentially be used in quantitative illumination analysis and velocity model building. The GSA could be adopted easily for frequency-domain wavefield propagators and time-domain propagators. Furthermore, the GSA can generate any number of stained wavefields. Numerical experiments demonstrate these features of the GSA, and we apply this method in target-oriented modeling and imaging as well as obtaining amplitude-preserved stained wavefields and higher S/Ns in images of target structures.

Dirty salt velocity inversion: The road to a clearer subsalt image

Geophysics ◽  
2011 ◽  
Vol 76 (5) ◽  
pp. WB169-WB174 ◽  
Author(s):  
Shuo Ji ◽  
Tony Huang ◽  
Kang Fu ◽  
Zhengxue Li
Keyword(s):  
Model Building ◽  
Synthetic Data ◽  
Velocity Model ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Data Set ◽  
Velocity Inversion ◽  
Time Migration ◽  
And Migration ◽  
Subsalt Imaging

For deep-water Gulf of Mexico, accurate salt geometry is critical to subsalt imaging. This requires the definition of both external and internal salt geometries. In recent years, external salt geometry (i.e., boundaries between allochthonous salt and background sediment) has improved a great deal due to advances in acquisition, velocity model building, and migration algorithms. But when it comes to defining internal salt geometry (i.e., intrasalt inclusions or dirty salt), no efficient method has yet been developed. In common industry practices, intrasalt inclusions (and thus their velocity anomalies) are generally ignored during the model building stages. However, as external salt geometries reach higher levels of accuracy, it becomes more important to consider the once-ignored effects of dirty salt. We have developed a reflectivity-based approach for dirty salt velocity inversion. This method takes true-amplitude reverse time migration stack volumes as input, then estimates the dirty salt velocity based on reflectivity under a 1D assumption. Results from a 2D synthetic data set and a real 3D Wide Azimuth data set demonstrated that the reflectivity inversion scheme significantly improves the subsalt image for certain areas. In general, we believe that this method produces a better salt model than the traditional clean salt velocity approach.

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