scholarly journals Acquisition geometry analysis in complex 3D media

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. Q43-Q58 ◽  
Author(s):  
E. J. van Veldhuizen ◽  
G Blacquière ◽  
A. J. Berkhout
Keyword(s):  
Grid Point ◽  
Seismic Inversion ◽  
Image Resolution ◽  
Seismic Exploration ◽  
Equation Modeling ◽  
Subsurface Structures ◽  
Detector Geometry ◽  
And Migration ◽  
Double Focusing ◽  
Geometry Analysis

Increasingly, we must deal with complex subsurface structures in seismic exploration, often resulting in poor illumination and, therefore, poor image quality. Consequently, it is desirable to take into consideration the effects of wave propagation in the subsurface structure when designing an acquisition geometry. We developed a new, model-based implementation of the previously introduced focal-beam analysis method. The method’s objective is to provide quantitative insight into the combined influence of acquisition geometry, overburden structure, and migration operators on image resolution and angle-dependent amplitude accuracy. This is achieved by simulation of migrated grid-point responses using focal beams. Note that the seismic response of any subsurface can be composed of a linear sum of grid-point responses. The focal beams have been chosen because any migration process represents double focusing. In addition, the focal source beam and focal detector beam relate migration quality to illumination properties of the source geometry and sensing properties of the detector geometry, respectively. Wave-equation modeling ensures that frequency-dependent effects in the seismic-frequency range are incorporated. We tested our method by application to a 3D salt model in the Gulf of Mexico. Investigation of well-sampled, all-azimuth, long-offset acquisition geometries revealed fundamental illumination and sensing limitations. Further results exposed the shortcomings of narrow-azimuth data acquisition. The method also demonstrates how acquisition-related amplitude errors affect seismic inversion results.

Migration deconvolution using domain decomposition

Geophysics ◽  
2021 ◽  
pp. 1-61
Author(s):  
Luana Nobre Osorio ◽  
Bruno Pereira-Dias ◽  
André Bulcão ◽  
Luiz Landau
Keyword(s):  
Domain Decomposition ◽  
Least Squares ◽  
Iterative Algorithms ◽  
Image Resolution ◽  
Image Domain ◽  
Hessian Operator ◽  
Incomplete Coverage ◽  
And Migration ◽  
Least Squares Migration ◽  
Data Frequency

Least-squares migration (LSM) is an effective technique for mitigating blurring effects and migration artifacts generated by the limited data frequency bandwidth, incomplete coverage of geometry, source signature, and unbalanced amplitudes caused by complex wavefield propagation in the subsurface. Migration deconvolution (MD) is an image-domain approach for least-squares migration, which approximates the Hessian operator using a set of precomputed point spread functions (PSFs). We introduce a new workflow by integrating the MD and the domain decomposition (DD) methods. The DD techniques aim to solve large and complex linear systems by splitting problems into smaller parts, facilitating parallel computing, and providing a higher convergence in iterative algorithms. The following proposal suggests that instead of solving the problem in a unique domain, as conventionally performed, we split the problem into subdomains that overlap and solve each of them independently. We accelerate the convergence rate of the conjugate gradient solver by applying the DD methods to retrieve a better reflectivity, which is mainly visible in regions with low amplitudes. Moreover, using the pseudo-Hessian operator, the convergence of the algorithm is accelerated, suggesting that the inverse problem becomes better conditioned. Experiments using the synthetic Pluto model demonstrate that the proposed algorithm dramatically reduces the required number of iterations while providing a considerable enhancement in the image resolution and better continuity of poorly illuminated events.

Diffraction imaging by focusing‐defocusing: An outlook on seismic superresolution

Geophysics ◽  
2004 ◽  
Vol 69 (6) ◽  
pp. 1478-1490 ◽  
Author(s):  
V. Khaidukov ◽  
E. Landa ◽  
T. J. Moser
Keyword(s):  
Image Resolution ◽  
Correct Identification ◽  
Structural Elements ◽  
Large Area ◽  
Specular Reflections ◽  
Full Wave ◽  
Geological Discontinuities ◽  
Diffraction Imaging ◽  
And Migration ◽  
Traditional Image

Diffractions always need more advertising. It is true that conventional seismic processing and migration are usually successful in using specular reflections to estimate subsurface velocities and reconstruct the geometry and strength of continuous and pronounced reflectors. However, correct identification of geological discontinuities, such as faults, pinch‐outs, and small‐size scattering objects, is one of the main objectives of seismic interpretation. The seismic response from these structural elements is encoded in diffractions, and diffractions are essentially lost during the conventional processing/migration sequence. Hence, we advocate a diffraction‐based, data‐oriented approach to enhance image resolution—as opposed to the traditional image‐oriented techniques, which operate on the image after processing and migration. Even more: it can be shown that, at least in principle, processing of diffractions can lead to superresolution and the recovery of details smaller than the seismic wavelength. The so‐called reflection stack is capable of effectively separating diffracted and reflected energy on a prestack shot gather by focusing the reflection to a point while the diffraction remains unfocused over a large area. Muting the reflection focus and defocusing the residual wavefield result in a shot gather that contains mostly diffractions. Diffraction imaging applies the classical (isotropic) diffraction stack to these diffraction shot gathers. This focusing‐muting‐defocusing approach can successfully image faults, small‐size scattering objects, and diffracting edges. It can be implemented both in model‐independent and model‐dependent contexts. The resulting diffraction images can greatly assist the interpreter when used as a standard supplement to full‐wave images.

scholarly journals Petrophysics and paradigms of oil and gas geology

Georesursy ◽  
2020 ◽  
pp. 10-14
Author(s):  
Aleksey M. Khitrov ◽  
Elena M. Danilova ◽  
Irina N. Konovalova ◽  
Marina N. Popova
Keyword(s):  
Oil And Gas ◽  
Seismic Exploration ◽  
Resource Base ◽  
Well Production ◽  
Exploration And Production ◽  
Light Oil ◽  
New Ideas ◽  
And Migration ◽  
Hydrocarbon Deposits ◽  
Current Paradigm

The main provisions of the current paradigm of prospecting, exploration and production of hydrocarbons, which are based on petrophysics and seismic exploration, are considered. It is shown that within its framework it is possible to apply any new ideas about the structure of natural reservoirs, the origin and migration of hydrocarbons. This paradigm will make it possible to move to the preparation of a qualitatively new resource base of the oil and gas complex through the discovery and development of hydrocarbon deposits in the best natural reservoirs with the best petrophysical parameters, high density of light oil and gas reserves, and high well production rates. New highly profitable hydrocarbon deposits will be discovered in areas with developed infrastructure, mainly in well-known oil and gas provinces.

Interpolation method based on pattern-feature correlation

Geophysics ◽  
2021 ◽  
pp. 1-87
Author(s):  
Bo Yu ◽  
Hui Zhou ◽  
Wenling Liu ◽  
Lingqian Wang ◽  
Hanming Chen
Keyword(s):  
Interpolation Method ◽  
Traditional Approach ◽  
Seismic Profile ◽  
Seismic Inversion ◽  
Seismic Exploration ◽  
Multiple Point ◽  
Well Log ◽  
Weighted Interpolation ◽  
Log Data ◽  
Feature Correlation

Reasonable low-wavenumber initial models are essential for reducing the non-uniqueness of seismic inversion. A traditional approach to estimating the low-wavenumber models of elastic parameters is well-log interpolation. However, complex geological structures decrease the accuracy of this method. To overcome these challenges in building prior models, we propose an interpolation method based on pattern-feature correlation inspired by multiple-point geostatistics (MPG). In the proposed interpolation method, we scan a stacked seismic profile using a predefined data template to obtain a geological pattern around each node in the seismic profile. Each pattern is then converted into several filter-scores with the filters defined in the MPG algorithm of the filter-based simulation (FILTERSIM). We calculate the correlation coefficients of the filter-scores among different patterns for the various nodes and define them as the pattern feature correlations (PFCs). We construct the initial models from well-log data based on the weighted interpolation method, where the weighting factors are precisely determined by the PFCs. We build the initial models using the proposed method for both synthetic and field data to demonstrate its effectiveness. To verify the validity of the initial models, we apply them to Bayesian linearized inversion. The accuracy of the interpolation and inversion results verify the excellent performance of the proposed interpolation method. The proposed method provides a novel and convenient approach that combines seismic and well-log data, which contributes to both seismic exploration and geological modeling.

AVO detectability against tuning and stretching artifacts

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 494-503 ◽  
Author(s):  
Wenjie Dong
Keyword(s):  
Seismic Data ◽  
Synthetic Data ◽  
Seismic Exploration ◽  
Inversion Algorithm ◽  
Amplitude Variation With Offset ◽  
Logical Point ◽  
Anomalous Reflection ◽  
Ricker Wavelet ◽  
And Migration ◽  
And Inversion

The [Formula: see text] of hydrocarbon‐bearing sediments normally deviates from the [Formula: see text] trend of the background rocks. This causes anomalous reflection amplitude variation with offset (AVO) in the seismic data. The estimation of these AVOs is inevitably affected by wave propagation effects and inversion algorithm limitations, such as thin‐bed tuning and migration stretch. A logical point is to determine the minimum [Formula: see text] change required for an anomalous AVO to be detectable beyond the background tuning and stretching effects. Assuming Ricker wavelet for the seismic data, this study addresses this point by quantifying the errors in the intercept/slope estimate. Using these results, two detectability conditions are derived. Denoting the background [Formula: see text] by γ and its variation by δγ, the thin‐bed parameter (thickness/wavelength) by ξ, the maximum background intercept closest to the AVO by |A|max, and the thin‐bed intercept value by |A|thin the two conditions are [Formula: see text] [Formula: see text] for detectability against stretching and tuning plus stretching, respectively. Tests on synthetic data confirm their validity and accuracy. These conditions provide a quantitative guideline for evaluating AVO applicability and effectiveness in seismic exploration. They can eliminate some of the subjectivity when interpreting AVO results in different attribute spaces. To improve AVO detectability, a procedure is suggested for removing the tuning and stretching effects.

SEISMIC EXPLORATION OF THE DENVER‐JULESBURG BASIN

Geophysics ◽  
1952 ◽  
Vol 17 (2) ◽  
pp. 334-343
Author(s):  
B. F. Rummerfield
Keyword(s):  
Seismic Activity ◽  
Resolving Power ◽  
Seismic Exploration ◽  
Velocity Variation ◽  
Seismic Method ◽  
Subsurface Structures ◽  
Weathered Zone ◽  
Recent Developments ◽  
Elevation Changes

Recent developments in northeastern Colorado and southwestern Nebraska have resulted in a marked increase in seismic activity within the Denver‐Julesburg Basin. The low relief of many of the subsurface structures, coupled with the extraneous effects of weathered zone, elevation changes, surface deposits, and velocity variation taxes the resolving power of the seismic method and the interpretative ability of the geophysicist.

Unexplored deepwater basins of North Andaman Sea

2020 ◽  
Vol 39 (8) ◽  
pp. 551-557
Author(s):  
Rajesh Kalra ◽  
Roberto Fainstein ◽  
Srinivas Chandrashekar
Keyword(s):  
Seismic Velocity ◽  
State Of The Art ◽  
Far East ◽  
Seismic Inversion ◽  
Andaman Sea ◽  
Seismic Exploration ◽  
Carbonate Platforms ◽  
The North ◽  
Northern Edge ◽  
Back Arc

Deepwater basins of the North Andaman Sea in the northern edge of the Far East Archipelago were assessed recently by state-of-the-art seismic technology. The North Andaman Sea embraces several Tertiary basins consisting of a forearc basin, a volcanic arc, and a back-arc basin. Their massive but largely unknown stratigraphy consists of deeper Neogene lacustrine and deltaic sediments that infill basal synrift half-grabens, blanketed by massive sequences of the Late Oligocene, Miocene, and recent strata. In the extensional forearc, the deeper seismic marker horizons were structurally mapped and identified by acoustic impedance contrasts as carbonates, mass-transport complexes, synrift, and basement. The shallower Pliocene and Pleistocene sequences are dominated by low-seismic-velocity hemipelagic clays that were investigated using seismic attributes and seismic inversion. In the back arc, the relatively larger graben features were affected by tectonic inversion contemporaneous with the foundering of the basin into deep water in the Late Miocene. In the forearc and back arc, main hydrocarbon plays are the rimmed Early Miocene carbonate platforms, the paralic and deltaic sediments beneath the platform, and the deepwater clastics of hemipelagic clays and sands that form the dominant strata of the Mio-Pliocene. This modern seismic exploration involved acquisition, processing, and interpretation to assess the hydrocarbon prospectivity of undrilled deepwater regions in the forearc and back arc.

Diffraction tomography applied to crosshole and VSP seismic data

1989 ◽  
Vol 20 (2) ◽  
pp. 169
Author(s):  
J.A. Young
Keyword(s):  
Seismic Data ◽  
A Priori ◽  
Tomographic Reconstruction ◽  
Synthetic Data ◽  
Scattered Wave ◽  
Seismic Inversion ◽  
Image Resolution ◽  
Fourier Domain ◽  
Diffraction Tomography ◽  
Data Coverage

Diffraction tomography is an approach to seismic inversion which is analogous to f-k migration. It differs from f-k migration in that it attempts to obtain a more quantitative rather than qualitative image of the Earth's subsurface. Diffraction tomography is based on the generalized projection-slice theorem which relates the scattered wave field to the Fourier spectrum of the scatterer. Factors such as the survey geometry and the source bandwidth determine the data coverage in the spatial Fourier domain which in turn determines the image resolution. Limited view-angles result in regions of the spatial Fourier domain with no data coverage, causing the solution to the tomographic reconstruction problem to be nonunique. The simplistic approach is to assume the missing samples are zero and perform a standard reconstruction but this can result in images with severe artefacts. Additional a priori information can be introduced to the problem in order to reduce the nonuniqueness and increase the stability of the reconstruction. This is the standard approach used in ray tomography but it is not commonly used in diffraction tomography applied to seismic data.This paper shows the application of diffraction tomography to crosshole and VSP seismic data. Using synthetic data, the effects on image resolution of the survey geometry and the finite source bandwidth are examined and techniques for improving image quality are discussed.

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