scholarly journals Estimating broad trend of acoustic impedance profile from observed seismic reflection data using first principles only

2020 ◽  
Vol 17 (3) ◽  
pp. 475-483
Author(s):  
Animesh Mandal ◽  
Santi Kumar Ghosh
Keyword(s):  
First Principles ◽  
Acoustic Impedance ◽  
Seismic Reflection ◽  
Low Frequency ◽  
Singular Value ◽  
Earth Model ◽  
Depth Range ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Impedance Profile

Abstract Estimation of broad features or the low-frequency part of acoustic impedance from conventional reflection data is an essential yet challenging step for quantitative interpretation of seismic data due to its band-limited nature. A missing low-frequency part leads to non-uniqueness in the solution as well as placing restrictions in recovering the absolute impedance values. The current industry practice fills this gap by assuming either an initial impedance model or statistical restrictions on such a model. Doing away with such assumptions but using only first principles (Zoeppritz's equations) and homogeneous layered earth model, we have formulated a set of linear equations that are then solved for an unknown reflection co-efficient using singular value decomposition (SVD) approach with time sampled seismic trace as the input data. The present work demonstrates the effectiveness of reconstructing a broad and smooth impedance profile from first principles and even from acquired seismic reflection data. It also illustrates the method's success with real data, while determining in one go the unknown scale factor linking the true and the relative seismic amplitudes, and the smallest singular value to be retained in the solution from only the knowledge of the average value of the acoustic impedance over the depth range in question. Thus, the salient feature of this work is the ability to reconstruct an approximate impedance profile from field data without the aid of an initial model or statistical assumption on the reflectivity series. This approximate impedance profile can serve as a reliable initial input for more refined inversion or geologic interpretation.

Feasibility of approximate broadband estimation of acoustic impedance profile from first principles and band-limited reflection data

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. R57-R74 ◽  
Author(s):  
Santi Kumar Ghosh ◽  
Animesh Mandal
Keyword(s):  
First Principles ◽  
Acoustic Impedance ◽  
Linear Equations ◽  
Synthetic Data ◽  
Reflection Coefficients ◽  
Limited Data ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Impedance Profile ◽  
Band Limited

Because seismic reflection data are band limited, acoustic impedance profiles derived from them are nonunique. The conventional inversion methods counter the nonuniqueness either by stabilizing the answer with respect to an initial model or by imposing mathematical constraints such as sparsity of the reflection coefficients. By making a nominal assumption of an earth model locally consisting of a stack of homogeneous and horizontal layers, we have formulated a set of linear equations in which the reflection coefficients are the unknowns and the recursively integrated seismic trace constitute the data. Drawing only on first principles, the Zoeppritz equation in this case, the approach makes a frontal assault on the problem of reconstructing reflection coefficients from band-limited data. The local layer-cake assumption and the strategy of seeking a singular value decomposition solution of the linear equations counter the nonuniqueness, provided that the objective is to reconstruct a smooth version of the impedance profile that includes only its crude structures. Tests on synthetic data generated from elementary models and from measured logs of acoustic impedance demonstrated the efficacy of the method, even when a significant amount of noise was added to the data. The emergence of consistent estimates of impedance, approximating the original impedance, from synthetic data generated for several frequency bands has inspired our confidence in the method. The other attractive outputs of the method are as follows: (1) an accurate estimate of the impedance mean, (2) an accurate reconstruction of the direct-current (DC) frequency of the reflectivity, and (3) an acceptable reconstruction of the broad outline of the original impedance profile. These outputs can serve as constraints for either more refined inversions or geologic interpretations. Beginning from the restriction of band-limited data, we have devised a method that neither requires a starting input model nor imposes mathematical constraints on the earth reflectivity and still yielded significant and relevant geologic information.

scholarly journals NOISE ATTENUATION IN SEISMIC REFLECTION DATA COMBINING EMPIRICAL MODE DECOMPOSITION AND SVD FILTERING

2016 ◽  
Vol 34 (3) ◽  
Author(s):  
Felipe Da Mota Alves ◽  
Milton J. Porsani
Keyword(s):  
Empirical Mode Decomposition ◽  
Seismic Reflection ◽  
Seismic Noise ◽  
Singular Value ◽  
Noise Attenuation ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Mode Decomposition ◽  
General Frequency ◽  
Value Decomposition

ABSTRACT. Noises are common events in seismic reflection that have very striking features in the seismograms, hindering the data processing and interpretation. The attenuation of seismic noise is a challenge, in general frequency filters are employed, but they often do not show good results. The characteristic of noise...Keywords: seismic noise, Empirical Mode Decomposition, Singular Value Decomposition. RESUMO. Ruídos são eventos comuns na sísmica de reflexão que possuem características bem marcantes nos sismogramas, atrapalhando o processamento e interpretação dos dados. A atenuação de ruídos sísmicos é um desafio, em geral são utilizados filtros de...Palavras-chave: ruídos sísmicos, Decomposição em Modos Empíricos, Decomposição em Valores Singulares.

scholarly journals Interpretation of 3D Seismic Reflection Data to Reveal Stratigraphic Setting of the Reservoir of Mishrif Formation in Dujaila Oil Field, Southeast of Iraq

2021 ◽  
pp. 2250-2261
Author(s):  
Ahmed Muslim Khawaja ◽  
Jassim Muhammad Thabit
Keyword(s):  
Seismic Reflection ◽  
Seismic Analysis ◽  
Carbonate Platform ◽  
Low Frequency ◽  
Oil Field ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Carbonate Buildups ◽  
Depositional Models

     This research is an attempt to solve the ambiguity associated with the stratigraphic setting of the main reservoir (late Cretaceous) of Mishrif Formation in Dujaila oil field. This was achieved by studying a 3D seismic reflection post-stack data for an area of ​​602.62 Km2 in Maysan Governorate, southeast of Iraq. Seismic analysis of the true amplitude reflections, time maps, and 3D depositional models showed a sufficient seismic evidence that the Mishrif Formation produces oil from a stratigraphic trap of isolated reef carbonate buildups that were grown on the shelf edge of the carbonate platform, located in the area around the productive well Dujaila-1. The low-frequency attribute illustrated that it is restricted in the area around the productive well Dujaila-1, which confirmed the existence of reef porous carbonate buildups and hydrocarbon accumulation in this region. The pay zone of the reef mound trap extends for about 7 km from the well Dujaila-1 toward the southwest side and 4 km toward the well Dujaila-2, without reaching it, which is explaining why it was dry. Therefore, this area to the south of the productive well Dujaila-1 represents a good area for low-risk drilling. Consequently, the hydrocarbon system observed in the Dujaila oil field provides a new opportunity to explore and produce oil in Mishrif Formation in other areas on the flank of the productive structures and in flat areas situated on the belt of the carbonate platform edge.

Geostatistical seismic inversion for frontier exploration

2017 ◽  
Vol 5 (4) ◽  
pp. T477-T485 ◽  
Author(s):  
Ângela Pereira ◽  
Rúben Nunes ◽  
Leonardo Azevedo ◽  
Luís Guerreiro ◽  
Amílcar Soares
Keyword(s):  
Acoustic Impedance ◽  
Seismic Reflection ◽  
Seismic Inversion ◽  
Well Log ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Log Data ◽  
The Real ◽  
Reflection Data ◽  
Impedance Models

Numerical 3D high-resolution models of subsurface petroelastic properties are key tools for exploration and production stages. Stochastic seismic inversion techniques are often used to infer the spatial distribution of the properties of interest by integrating simultaneously seismic reflection and well-log data also allowing accessing the spatial uncertainty of the retrieved models. In frontier exploration areas, the available data set is often composed exclusively of seismic reflection data due to the lack of drilled wells and are therefore of high uncertainty. In these cases, subsurface models are usually retrieved by deterministic seismic inversion methodologies based exclusively on the existing seismic reflection data and an a priori elastic model. The resulting models are smooth representations of the real complex geology and do not allow assessing the uncertainty. To overcome these limitations, we have developed a geostatistical framework that allows inverting seismic reflection data without the need of experimental data (i.e., well-log data) within the inversion area. This iterative geostatistical seismic inversion methodology simultaneously integrates the available seismic reflection data and information from geologic analogs (nearby wells and/or analog fields) allowing retrieving acoustic impedance models. The model parameter space is perturbed by a stochastic sequential simulation methodology that handles the nonstationary probability distribution function. Convergence from iteration to iteration is ensured by a genetic algorithm driven by the trace-by-trace mismatch between real and synthetic seismic reflection data. The method was successfully applied to a frontier basin offshore southwest Europe, where no well has been drilled yet. Geologic information about the expected impedance distribution was retrieved from nearby wells and integrated within the inversion procedure. The resulting acoustic impedance models are geologically consistent with the available information and data, and the match between the inverted and the real seismic data ranges from 85% to 90% in some regions.

Shallow 3-D seismic reflection surveying: Data acquisition and preliminary processing strategies

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1434-1450 ◽  
Author(s):  
Frank Büker ◽  
Alan G. Green ◽  
Heinrich Horstmeyer
Keyword(s):  
Data Acquisition ◽  
Seismic Reflection ◽  
Full Range ◽  
Depth Range ◽  
Data Set ◽  
Processing Scheme ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Glacial Sediments ◽  
Reflection Data

A comprehensive strategy of 3-D seismic reflection data acquisition and processing has been used in a study of glacial sediments deposited within a Swiss mountain valley. Seismic data generated by a downhole shotgun source were recorded with single 30-Hz geophones distributed at 3 m × 3 m intervals across a 357 m × 432 m area. For most common‐midpoint (CMP) bins, traces covering a full range of azimuths and source‐receiver distances of ∼2 to ∼125 m were recorded. A common processing scheme was applied to the entire data set and to various subsets designed to simulate data volumes collected with lower density source and receiver patterns. Comparisons of seismic sections extracted from the processed 3-D subsets demonstrated that high‐fold (>40) and densely spaced (CMP bin sizes ⩽ 3 m × 3 m) data with relatively large numbers (>6) of traces recorded at short (<20 m) source‐receiver offsets were essential for obtaining clear images of the shallowest (<100 ms) reflecting horizons. Reflections rich in frequencies >100 Hz at traveltimes of ∼20 to ∼170 ms provided a vertical resolution of 3 to 6 m over a depth range of ∼15 to ∼150 m. The shallowest prominent reflection at 20 to 35 ms (∼15 to 27 m depth) originated from the boundary between a near‐surface sequence of clays/silts and an underlying unit of heterogeneous sands/gravels.

Ground‐roll suppression from deep crustal seismic reflection data using a wavelet‐based approach: A case study from western Canada

Geophysics ◽  
2004 ◽  
Vol 69 (4) ◽  
pp. 877-884 ◽  
Author(s):  
J. Kim Welford ◽  
Rongfeng Zhang
Keyword(s):  
Seismic Reflection ◽  
Low Frequency ◽  
Frequency Separation ◽  
Frequency Noise ◽  
Data Sets ◽  
Data Set ◽  
Dispersive Waves ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Ground Roll

Seismic reflection data sets recorded on land are often contaminated by coherent ground‐roll noise generated by the propagation of dispersive waves along the free surface. For crustal‐scale investigations, this ground‐roll contamination can be particularly harmful as the higher amplitude, low‐frequency noise overwhelms low‐frequency signals coming from deep reflectors. Consequently, conventional ground‐roll suppression techniques which rely on frequency separation of ground roll from signal become ineffective for crustal studies. This paper presents the successful use of a new 2D wavelet method based on frame theory (physical wavelet frame denoising) in removing ground roll from a deep 3D reflection data set intended for the study of upper crustal Precambrian mafic sills in southwestern Alberta, Canada.

Curvelet-based multiple prediction

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. WB255-WB263 ◽  
Author(s):  
Daniela Donno ◽  
Hervé Chauris ◽  
Mark Noble
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Low Frequency ◽  
Curvelet Transform ◽  
Point Of View ◽  
Directional Characteristic ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Local Plane ◽  
Multiple Prediction

The suppression of multiples is a crucial task when processing seismic reflection data. Using the curvelet transform for surface-related multiple prediction is investigated. From a geophysical point of view, a curvelet can be seen as the representation of a local plane wave and is particularly well suited for seismic data decomposition. For the prediction of multiples in the curvelet domain, first it is proposed to decompose the input data into curvelet coefficients. These coefficients are then convolved together to predict the coefficients associated with multiples, and the final result is obtained by applying the inverse curvelet transform. The curvelet transform offers two advantages. The directional characteristic of curvelets allows for exploitation of Snell’s law at the sea surface. Moreover, the possible aliasing in the predicted multiple is better managed by using the curvelet multiscale property to weight the prediction according to the low-frequency part of the data. 2D synthetic and field data examples show that some artifacts and aliasing effects are indeed reduced in the multiple prediction with the use of curvelets, thus allowing for an improved multiple subtraction result.

scholarly journals Composite damage zones in the subsurface

2020 ◽  
Vol 222 (1) ◽  
pp. 225-230 ◽  
Author(s):  
Zonghu Liao ◽  
Wei Li ◽  
Huayao Zou ◽  
Fang Hao ◽  
Kurt J Marfurt ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Depth Range ◽  
Tight Sandstone ◽  
Seismic Reflection Data ◽  
Intensity Mapping ◽  
Reflection Data ◽  
Composite Damage ◽  
Fracture Distribution ◽  
Earthquake Simulations ◽  
Dome Shape

SUMMARY The cumulative displacement by multiple slip events along faults may generate composite damage zones (CDZ) of increasing width, and could modify the hydraulic and mechanical properties of the faults. The internal architecture and fracture distribution within CDZs at the subsurface are analysed here by using seismic attributes of variance, curvature and dip-azimuth of the 3-D seismic reflection data from tight sandstone reservoirs in northeast Sichuan, China. The analysed faults intersect the reservoir within a depth range of 2.4–3.0 km. The damage intensity mapping revealed multiple CDZs with thicknesses approaching 1 km along faults ranging 3–15 km in length, and up to 1000 m of cumulative slip. The identification of numerous fault cores and associate damage zones led us to define three classes of CDZs: banded shape, box shape and dome shape. The mechanical strength contrasts and distortion of fault cores suggest potential weakening and strengthening (healing) mechanisms for formation of CDZs that can be extended to faulting processes and earthquake simulations.

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