Converted-wave Processing of an Ocean Bottom Cable Dataset from the Arabian Gulf

2014 ◽  
Author(s):  
M.J. Grimshaw ◽  
J.P. Holden ◽  
E. Murray ◽  
K. Shaukat ◽  
B. Beck ◽  
...  
Keyword(s):  
Arabian Gulf ◽  
Ocean Bottom ◽  
Converted Wave

scholarly journals Lithology estimation from a multicomponent 3D-4C OBC seismic survey over a clastic reservoir in the Arabian Gulf

GeoArabia ◽  
2008 ◽  
Vol 13 (1) ◽  
pp. 15-34
Author(s):  
Costas G. Macrides ◽  
Fernando A. Neves
Keyword(s):  
Arabian Gulf ◽  
Seismic Facies ◽  
Seismic Survey ◽  
Ocean Bottom ◽  
Converted Wave ◽  
Flip Flop ◽  
Time Migration ◽  
Dual Sensor ◽  
Seismic Facies Analysis ◽  
Reservoir Quality Index

ABSTRACT In 2002, Saudi Aramco conducted its first 3D, 4-component (4C) ocean-bottom cable (OBC) seismic survey in the Arabian Gulf. The main objective was to delineate the middle Cretaceous Upper Khafji Sand Stringers Reservoir overlying the massive Main Khafji Sand Reservoir in the Zuluf field. The Upper Khafji Sand Stringers Reservoir in the Wasia Formation is typically characterized by weak acoustic impedance contrasts. A pre-survey modeling study, based on the logs of compressional (P) and shear-wave (S) velocities (Vp and Vs), indicated that converted compressional-to-shear waves (P-S) could better-image the structure and stratigraphy of the target reservoir. Commensurate with the objectives of the experiment, a pilot 100-square-kilometer survey was acquired with an inline swath-shooting geometry that employed two seabed receiver cables, with a symmetric split-spread deployment of the 4-C sensors. The acquisition geometry consisted of six sail lines per swath with a single-boat, dual-source, flip-flop configuration. The data were processed through dual-sensor summation, horizontal-component rotation and P-P/P-S pre-stack time migration. Post-stack enhancement using non-stationary Gabor deconvolution proved beneficial in compensating for the missing high frequencies in the acquired converted-wave data. Well-to-seismic calibration for both P-P and P-S data at five wells aided in the interpretation of the data. Five horizons were interpreted and correlated between the P-P and P-S sections. The horizons were analyzed using both amplitude and interval times such that the lateral variations of the Vp/Vs ratio of the Upper Khafji Sand Stringers Reservoir could be mapped. A region of low Vp/Vs ratios in the northwest quadrant, obtained from the isochron interval-time analysis, was correlated with higher ‘net sand’ pay at a hidden well located in the middle of this region. These results were further corroborated by seismic facies analysis and provide a qualitative reservoir quality index in the Upper Khafji Sand Stringers Reservoir.

scholarly journals Converted-wave azimuth moveout

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. S99-S110
Author(s):  
Daniel A. Rosales ◽  
Biondo Biondi
Keyword(s):  
Seismic Data ◽  
Extreme Case ◽  
Ocean Bottom ◽  
Sampled Data ◽  
Computationally Efficient ◽  
Converted Wave ◽  
Data Set ◽  
Prestack Migration ◽  
Conversion Point ◽  
The Common

A new partial-prestack migration operator to manipulate multicomponent data, called converted-wave azimuth moveout (PS-AMO), transforms converted-wave prestack data with an arbitrary offset and azimuth to equivalent data with a new offset and azimuth position. This operator is a sequential application of converted-wave dip moveout and its inverse. As expected, PS-AMO reduces to the known expression of AMO for the extreme case when the P velocity is the same as the S velocity. Moreover, PS-AMO preserves the resolution of dipping events and internally applies a correction for the lateral shift between the common-midpoint and the common-reflection/conversion point. An implementation of PS-AMO in the log-stretch frequency-wavenumber domain is computationally efficient. The main applications for the PS-AMO operator are geometry regularization, data-reduction through partial stacking, and interpolation of unevenly sampled data. We test our PS-AMO operator by solving 3D acquisition geometry-regularization problems for multicomponent, ocean-bottom seismic data. The geometry-regularization problem is defined as a regularized least-squares-objective function. To preserve the resolution of dipping events, the regularization term uses the PS-AMO operator. Application of this methodology on a portion of the Alba 3D, multicomponent, ocean-bottom seismic data set shows that we can satisfactorily obtain an interpolated data set that honors the physics of converted waves.

scholarly journals COMPARISON OF TRAVEL-TIME APPROXIMATIONS FOR UNCONVENTIONAL RESERVOIRS FROM SANTOS BASIN

2017 ◽  
Vol 35 (4) ◽  
pp. 273 ◽  
Author(s):  
Nelson Ricardo Coelho Flores Zuniga ◽  
Eder Cassola Molina ◽  
Renato Luiz Prado
Keyword(s):  
Travel Time ◽  
Complexity Analysis ◽  
Numerical Study ◽  
Optimization Criterion ◽  
Hydrocarbon Exploration ◽  
Unconventional Reservoirs ◽  
Ocean Bottom ◽  
Converted Wave ◽  
Reflection Seismic ◽  
Multicomponent Seismic

ABSTRACT. The reflection seismic method is extremely important for the hydrocarbon exploration. With more complex geological structures, as the pre-salt from Santos Basin, the reservoir exploration becomes more challenging and the multicomponent seismic investigation improves its mapping and characterization. To obtain multicomponent seismic data of an offshore survey it is necessary to use the OBN (Ocean Bottom Nodes) technology. The converted wave behavior, the large offsets and the difference of datum between source and receptors for layered media, results in strong nonhyperbolic travel-time events. Furthermore, the complexity and peculiarities of some unconventional reservoirs found in the pre-salt also increase the difficulty to perform the velocity analysis. For these reasons, it is necessary to use nonhyperbolic multiparametric travel-time approximations to control the nonhyperbolicity. Here we perform the comparison of nonhyperbolic travel-time approximations of seismic reflection events derived from geological models. The numerical study was considered as an inverse problem and it was treated according to an optimization criterion. The complexity analysis was performed in order to understand the behavior of each approximation concerning the unicity. After the computation of the relative errors between the observed curve and the calculated curve for each nonhyperbolic approximation, it was possible to find out the one with the highest accuracy for the events tested here.  Keywords:  multicomponent, OBN, nonhyperbolic.RESUMO.Ométodo sísmico de reflexão é extremamente importante para a exploração de hidrocarbonetos. Comestruturas geológicasmais complexas, como o pré-sal da Bacia de Santos, a exploração de reservatórios se tornamais desafiadora e a utilização da sísmica multicomponente promove o mapeamento e caracterização estrutural. Para obter-se dados de sísmica multicomponente em um levantamento offshore é necessário utilizar a tecnologia OBN (Ocean Bottom Nodes ). O comportamento de ondas convertidas, longos afastamentos e diferença de datum entre fonte e receptor pra meios estratificados resultam em uma forte não-hiperbolicidade dos eventos de tempos de trânsito. Além disso, a complexidade e peculiaridades, de alguns reservatórios não convencionais encontrados no pré-sal, também aumentam a dificuldade em realizar a análise de velocidades. Por estes motivos, é necessário usar aproximações não-hiperbólicas multiparamétricas de tempos de trânsito para controlar os efeitos da não-hiperbolicidade. No presente trabalho, foi realizada a comparação de aproximações não-hiperbólicas de tempos de trânsito de eventos sísmicos de reflexão provenientes de modelos geológicos. O estudo numérico foi considerado como um problema inverso e foi tratado de acordo com um critério de otimização. A análise de complexidade foi realizada para compreender o comportamento de cada aproximação com respeito a unicidade. Após computar os erros relativos entre a curva observada e as calculadas com cada aproximação, foi possível descobrir a aproximação que apresentou maior precisão para os testes realizado.Palavras-chave: multicomponente, OBN, não-hiperbólicas.

Pilot study of multi‐component ocean bottom seismic in the Arabian Gulf

2001 ◽  
Author(s):  
A. Al‐Shamsi ◽  
O. Suwaina ◽  
G. Ajlani ◽  
A. Ebed ◽  
M. Al‐Kabbi ◽  
...  
Keyword(s):  
Pilot Study ◽  
Arabian Gulf ◽  
Ocean Bottom

Geophysics in the high school STEM setting

2019 ◽  
Vol 38 (11) ◽  
pp. 873-877
Author(s):  
William Doenges ◽  
Sydney Potts ◽  
Christopher Rathman ◽  
Cody Winters ◽  
Warren Neff
Keyword(s):  
High School ◽  
Compressional Wave ◽  
Independent Study ◽  
Ocean Bottom ◽  
Science Fair ◽  
Converted Wave ◽  
New Science ◽  
School Year ◽  
Seismic Acquisition ◽  
Design For Science

In 2014, Bartlesville High School in Bartlesville, Oklahoma, USA, started an advanced math applications class as part of its new science, technology, engineering, and math (STEM) program. Selected exploration geophysics topics were incorporated as part of the class. Four of the class students in the 2017–2018 school year completed independent study of various topics in seismic acquisition design for science fair projects. The contents of this paper are the findings of those science fair projects. Contents include generating evenly distributed fold for compressional wave surveys (P-P), evenly distributed fold for converted-wave surveys (P-S), evenly distributed fold for ocean-bottom-cable/seismometer surveys (P-P), and offset/depth relations for validity of using the asymptotic approximation for converted-wave surveys (P-S).

Elastic 3D PS converted-wave Gaussian beam migration

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. S213-S225 ◽  
Author(s):  
Xuelei Li ◽  
Weijian Mao ◽  
Xingchen Shi ◽  
Yubo Yue
Keyword(s):  
Elastic Wave ◽  
Gaussian Beam ◽  
Wave Equations ◽  
Unit Vector ◽  
P Wave ◽  
Ocean Bottom ◽  
Converted Wave ◽  
Effective Work ◽  
Gaussian Beam Migration ◽  
Wave Migration

Elastic-wave migration is a desirable technique because it can image the structure of the earth more accurately. We develop a new elastic Gaussian beam migration method with 3D three component (3D-3C) seismic data that focuses on a complex PS-converted wave. Based on the elastic-wave equations and complete boundary conditions, we derive effective work formulas for an accurate multimode wave downward continuation for the free-space, ocean-bottom, and free-surface models. We separate the PS-wave into linear-polarized P-S1 and P-S2 waves to simplify the expression and derivation of the migration. To image the vectorial wave directly and solve the reverse-polarity issue, we use the crosscorrelations of P-wave divergence and PS-wave curl operators as the 3D P- and PS-imaging conditions, and we develop a unit vector to define the rotation direction of the PS-wave. With our approach, 3D-3C multimode waves are automatically decomposed to P- and PS-waves during the migration without the need for prior data separation, which not only reduces the crosstalk noise caused by inaccurate multimode wave decomposition but also decreases the processing cost. Applications of this method to two 3D-3C synthetic examples indicate successful PS-wave migration. Also, confirming that the PS-image can be constructed by summing the P-S1 and P-S2 images and is independent of the choice of the ray-centered local coordinates validates this method.

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