scholarly journals ANALYSIS OF SEISMIC ATTRIBUTES TO RECOGNIZE BOTTOM SIMULATING REFLECTORS IN THE FOZ DO AMAZONAS BASIN, NORTHERN BRAZIL

2019 ◽  
Vol 37 (1) ◽  
pp. 43
Author(s):  
Laisa da Fonseca Aguiar ◽  
Antonio Fernando Menezes Freire ◽  
Luiz Alberto Santos ◽  
Ana Carolina Ferreira Dominguez ◽  
Eloíse Helena Policarpo Neves ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Seismic Reflection ◽  
Seismic Attributes ◽  
Second Derivative ◽  
Seismic Section ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Bottom Simulating Reflectors ◽  
Northern Portion ◽  
Seismic Amplitudes

ABSTRACT. Foz do Amazonas basin is located at the northern portion of the Brazilian Equatorial Margin, along the coastal zone of Amapá and Pará states. This basin has been subjected to several studies, and the presence of gas hydrates has been demonstrated locally through sampling, and over broader areas using seismic reflection data. Seismic reflection is one method to identify the occurrence of gas hydrates, as they give rise to well-marked reflectors that simulate the seafloor, known as Bottom Simulating Reflectors (BSR). This study aims to investigate BSRs associated with the presence of methane hydrates in the Foz do Amazonas Basin through the application of seismic attributes. It was compared seismic amplitudes from the seafloor and the BSR to validate the inferred seismic feature. Then, Envelope and Second Derivative were chosen for highlighting the BSR in seismic section. The results showed an inversion of polarities in the signal between the seafloor (positive polarity) and the BSR (negative polarity). The integrated use of these approaches allowed validating the level of the BSR in line 0239-0035 and inferring the presence of gas hydrates, revealing to be a useful tool for interpreting the distribution of the gas hydrates in the Foz do Amazonas Basin.Keywords: Gas hydrates, envelope, second derivative of envelope, Brazilian Equatorial Margin.RESUMO. A Bacia da Foz do Amazonas é localizada na porção norte da Margem Equatorial Brasileira, ao longo da zona de costa dos estados do Amapá e do Pará. A presença de hidratos de gás é comprovada localmente através de amostragem, e em áreas mais distantes através de dados de sísmica de reflexão. A sísmica de reflexão é eficaz para identificar hidratos de gás, pois refletores que simulam o fundo do mar, Bottom Simulating Reflectors (BSR), são utilizados para inferir a presença dos hidratos de metano. Este estudo pretende identificar feições sísmicas associadas aos hidratos de metano na Bacia da Foz do Amazonas através da aplicação de atributos sísmicos. Foram comparadas as amplitudes sísmicas do fundo do mar e do BSR para validar a feição sísmica inferida. Então, os atributos Envelope e Segunda Derivada do Envelope foram escolhidos por destacarem o BSR. Os resultados mostraram uma inversão das polaridades no sinal entre o fundo do mar (positivo) e o BSR (negativo). O uso integrado dessas abordagens valida a localização do BSR na linha 0239-0035 e infere a ocorrência de hidratos de gás, revelando ser uma ferramenta útil para interpretação da distribuição de hidratos de gás na Bacia da Foz do Amazonas.Palavras-chave: Hidratos de metano, envelope, segunda derivada do envelope, Margem Equatorial Brasileira.

scholarly journals Gas Hydrates in the southern Jalisco subduction zone as evidenced by bottom simulating reflectors in Multichannel Seismic Reflection Data of the 2002 BART/FAMEX campaign

2012 ◽  
Vol 51 (4) ◽  
Author(s):  
William L. Bandy ◽  
Carlos A. Montera-Gutiérrez
Keyword(s):  
Subduction Zone ◽  
Gas Hydrates ◽  
Seismic Reflection ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Bottom Simulating Reflectors ◽  
Multichannel Seismic Reflection ◽  
Multichannel Seismic Reflection Data

Evidencia de la presencia de hidratos de gas en forma de reflector que simula el fondo marino (BRS) es observado en un perfil sísmico multicanal, México. Los reflectores son encontrados a 0.4 segundos (en el tiempo de viaje doble) bajo el reflector del fondo marino y se extiende a lo largo de 7 km del perfil. Este resultado aunado a otros resultados previos en la parte norte de la zona de subducción de Jalisco sugiere que los hidratos de gas pudieran existir en la región del talud continental de toda la zona de subducción de Jalisco, sin embargo se necesitan mas datos de reflexión sísmica para verificar esta aseveración.

Shallow seismic reflection study of a glaciated valley

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1395-1407 ◽  
Author(s):  
Frank Büker ◽  
Alan G. Green ◽  
Heinrich Horstmeyer
Keyword(s):  
Seismic Reflection ◽  
High Amplitude ◽  
Data Sets ◽  
Seismic Section ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Northern Switzerland ◽  
Reflection Data ◽  
Shallow Seismic ◽  
Glaciated Valley

Shallow seismic reflection data were recorded along two long (>1.6 km) intersecting profiles in the glaciated Suhre Valley of northern Switzerland. Appropriate choice of source and receiver parameters resulted in a high‐fold (36–48) data set with common midpoints every 1.25 m. As for many shallow seismic reflection data sets, upper portions of the shot gathers were contaminated with high‐amplitude, source‐generated noise (e.g., direct, refracted, guided, surface, and airwaves). Spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source‐generated noise, and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections. Resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi‐continuous reflection zones. The uppermost reflection zone at 20 to 50 ms (∼15 to ∼40 m depth) originated from a boundary between glaciolacustrine clays/silts and underlying glacial sands/gravels (till) deposits. Of particular importance was the discovery that the deepest part of the valley floor appeared on the seismic section at traveltimes >180 ms (∼200 m), approximately twice as deep as expected. Constrained by information from boreholes adjacent to the profiles, the various seismic units were interpreted in terms of unconsolidated glacial, glaciofluvial, and glaciolacustrine sediments deposited during two principal phases of glaciation (Riss at >100 000 and Würm at ∼18 000 years before present).

scholarly journals Using Seismic Attributes in seismotectonic research: an application to the Norcia's Mw = 6.5 earthquake (30th October 2016) in Central Italy

2019 ◽  
Author(s):  
Maurizio Ercoli ◽  
Emanuele Forte ◽  
Massimiliano Porreca ◽  
Ramon Carbonell ◽  
Cristina Pauselli ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Central Italy ◽  
Seismic Attributes ◽  
Seismic Attribute ◽  
Data Set ◽  
Epicentral Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Reflection Data ◽  
Attribute Analysis

Abstract. In seismotectonic studies, seismic reflection data are a powerful tool to unravel the complex deep architecture of active faults. Such tectonic structures are usually mapped at surface through traditional geological surveying whilst seismic reflection data may help to trace their continuation from the near-surface down to hypocentral depth. In this study, we propose the application of the seismic attributes technique, commonly used in seismic reflection exploration by oil industry, to seismotectonic research for the first time. The study area is a geologically complex region of Central Italy, recently struck by a long-lasting seismic sequence including a Mw 6.5 main-shock. A seismic reflection data-set consisting of three vintage seismic profiles, currently the only available across the epicentral zone, constitutes a singular opportunity to attempt a seismic attribute analysis. This analysis resulted in peculiar seismic signatures which generally correlate with the exposed surface geologic features, and also confirming the presence of other debated structures. These results are critical, because provide information also on the relatively deep structural setting, mapping a prominent, high amplitude regional reflector that marks the top basement, interpreted as important rheological boundary. Complex patterns of high-angle discontinuities crossing the reflectors have been also identified. These dipping fabrics are interpreted as the expression of fault zones, belonging to the active normal fault systems responsible for the seismicity of the region. This work demonstrates that seismic attribute analysis, even if used on low-quality vintage 2D data, may contribute to improve the subsurface geological interpretation of areas characterized by high seismic potential.

The use of seismic modeling for the geologic interpretation of deep seismic reflection data with low signal-to-noise ratios

2017 ◽  
Vol 5 (1) ◽  
pp. T23-T31 ◽  
Author(s):  
Ionelia Panea ◽  
Stefan Prisacari ◽  
Victor Mocanu ◽  
Mihnea Micu ◽  
Marius Paraschivoiu
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Seismic Section ◽  
Seismic Reflection Data ◽  
Deep Seismic Reflection ◽  
Subsurface Geology ◽  
Reflection Data ◽  
Geologic Interpretation ◽  
Romanian Carpathians ◽  
Seismic Data Acquisition

We have performed a deep seismic reflection study, DACIA-PLAN, based on the data recorded along a crooked line across the southeastern Romanian Carpathians. The signal-to-noise ratio (S/N) of these data varies along the seismic profile, and its variation is considered to be an effect of the rough topography, complex subsurface geology, and varying surface conditions encountered during seismic data acquisition. The migrated time section that covers the mountainous area is clear, without visible reflections, making the geologic interpretation very difficult. We used a seismic modeling technique to explain the poor S/N of the recorded data and to generate synthetic seismic sections that can be useful for the geologic interpretation of the field seismic section (migrated time section). We used ray-tracing modeling to obtain the expected seismic expression of horizons of interest. Subsurface illumination modeling indicates that the complex subsurface geology and irregularly deployed sources and receivers are responsible for the incomplete and/or uneven illumination of the subsurface and can lead to strong amplitude variations. We then used 2.5D acoustic finite-difference modeling to analyze the effect of a crooked line on seismic wave propagation. The synthetic shot gathers prove that crooked line arrival times for reflected and head waves contain static time shifts relative to a straight line regular sampling geometry. Some geologic interfaces of interest are not well-imaged on the synthetic seismic section, and this is considered to be an effect of poor positioning during seismic data acquisition. We used the velocity model from the tomographic inversion of first-arrival traveltimes and synthetic and field crooked line deep seismic reflection data to create a structural image for the southeastern Romanian Carpathians and the Focsani Basin, which tie well with the geologic model built for this area on the basis of geologic and well data only.

scholarly journals 3D Seismic Reflection Study of Al-Akhadeir Area, Southwestern Iraq

2020 ◽  
pp. 3024-3035
Author(s):  
Kamal K. Ali ◽  
Gassak F. Kadhim
Keyword(s):  
Seismic Reflection ◽  
Synthetic Seismogram ◽  
Well Logs ◽  
3D Seismic ◽  
Seismic Section ◽  
Entire Area ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Interpretation Process

This study includes structural and stratigraphic interpretation of 3D seismic reflection data for Zubair Formation (L. Cretaceous) within Al-Akhadeir area, southwestern Iraq (Karbala Governorate). Depending on the 3D seismic reflection interpretation process, and based on the synthetic seismogram  and well logs data, two horizons were identified and selected (top and base Zubair  reflectors). These horizons were followed up over the entire area in order to obtain structural and stratigraphic settings. TWT, depth, and velocity maps for the base and top Zubair Formation were constructed. From the interpretation of these maps and based on the seismic section, the study concluded that there are some enclosures that represent anticline in the NW of the horizon and syncline in the NE, while the nose structure appears in the middle of the horizon and trends N-S. The horizon represents a progradational with sigmoid configuration.. Other seismic structural phenomena were recognized in this part of the area, such as flat spot, down lap, and top lap, which give indicators of potential hydrocarbon accumulations

Stappen High-Bjørnøya tectono-sedimentary element, Barents Sea

2021 ◽  
pp. M57-2016-24
Author(s):  
F. Tsikalas ◽  
O. A. Blaich ◽  
J. I. Faleide ◽  
S. Olaussen
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Barents Sea ◽  
Seismic Reflection Data ◽  
Structural Inheritance ◽  
Reflection Data ◽  
Geological Information ◽  
Northern Portion ◽  
Early Cenozoic ◽  
Shallow Platform

AbstractThe Stappen High-Bjørnøya tectono-sedimentary element (TSE) is located in the western Barents Shelf and is one of the prominent tectonic elements in the area. The Stappen High comprises a shallow platform, and Bjørnøya forms its highest point with exposed outcrops. Modern seismic reflection data of improved quality in the southern part of the TSE and vintage seismic data in the northern portion are utilised. Together with updated geological information at Bjørnøya, the study provides insights into the Palaeozoic to early Cenozoic evolution of the Stappen High-Bjørnøya TSE. In this context, we discuss structural inheritance, the rift development, and we account for confirmed and potential hydrocarbon systems and plays.

scholarly journals Fault interpretation in seismic reflection data: an experiment analysing the impact of conceptual model anchoring and vertical exaggeration

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1651-1662 ◽  
Author(s):  
Juan Alcalde ◽  
Clare E. Bond ◽  
Gareth Johnson ◽  
Armelle Kloppenburg ◽  
Oriol Ferrer ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Conceptual Models ◽  
Seismic Section ◽  
Seismic Reflection Data ◽  
Reflection Seismic ◽  
Reflection Data ◽  
Interpretation Process ◽  
Fault Interpretation ◽  
The Impact

Abstract. The use of conceptual models is essential in the interpretation of reflection seismic data. It allows interpreters to make geological sense of seismic data, which carries inherent uncertainty. However, conceptual models can create powerful anchors that prevent interpreters from reassessing and adapting their interpretations as part of the interpretation process, which can subsequently lead to flawed or erroneous outcomes. It is therefore critical to understand how conceptual models are generated and applied to reduce unwanted effects in interpretation results. Here we have tested how interpretation of vertically exaggerated seismic data influenced the creation and adoption of the conceptual models of 161 participants in a paper-based interpretation experiment. Participants were asked to interpret a series of faults and a horizon, offset by those faults, in a seismic section. The seismic section was randomly presented to the participants with different horizontal–vertical exaggeration (1:4 or 1:2). Statistical analysis of the results indicates that early anchoring to specific conceptual models had the most impact on interpretation outcome, with the degree of vertical exaggeration having a subdued influence. Three different conceptual models were adopted by participants, constrained by initial observations of the seismic data. Interpreted fault dip angles show no evidence of other constraints (e.g. from the application of accepted fault dip models). Our results provide evidence of biases in interpretation of uncertain geological and geophysical data, including the use of heuristics to form initial conceptual models and anchoring to these models, confirming the need for increased understanding and mitigation of these biases to improve interpretation outcomes.

scholarly journals Using seismic attributes in seismotectonic research: an application to the Norcia <i>M</i><sub>w</sub> = 6.5 earthquake (30 October 2016) in central Italy

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 329-348 ◽  
Author(s):  
Maurizio Ercoli ◽  
Emanuele Forte ◽  
Massimiliano Porreca ◽  
Ramon Carbonell ◽  
Cristina Pauselli ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Central Italy ◽  
Seismic Attributes ◽  
Tectonic Structures ◽  
Seismic Attribute ◽  
Epicentral Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Reflection Data ◽  
Attribute Analysis

Abstract. In seismotectonic studies, seismic reflection data are a powerful tool to unravel the complex deep architecture of active faults. Such tectonic structures are usually mapped at the surface through traditional geological surveying, whilst seismic reflection data may help to trace their continuation from the near surface down to hypocentral depths. On seismic reflection data, seismic attributes are commonly used by the oil and gas industry to aid exploration. In this study, we propose using seismic attributes in seismotectonic research for the first time. The study area is a geologically complex region of central Italy, struck during 2016–2017 by a long-lasting seismic sequence, including a Mw 6.5 main shock. Three vintage seismic reflection profiles are currently the only ones available at the regional scale across the epicentral zone. These represent a singular opportunity to attempt a seismic attribute analysis by running attributes like the “energy” and the “pseudo-relief”. Our results are critical, as they provide information on the relatively deep structural setting, mapping a prominent, high-amplitude regional reflector interpreted as the top of basement, which is an important rheological boundary. Complex patterns of high-angle discontinuities crossing the reflectors have also been identified by seismic attributes. These steeply dipping fabrics are interpreted as the expression of fault zones belonging to the active normal fault systems responsible for the seismicity of the region. Such peculiar seismic signatures of faulting are consistent with the principal geological and tectonic structures exposed at surface. In addition, we also provide convincing evidence of an important primary tectonic structure currently debated in the literature (the Norcia antithetic fault) as well as several buried secondary fault splays. This work demonstrates that seismic attribute analysis, even if used on low-quality vintage 2D data, may contribute to improving the subsurface geological interpretation in areas characterized by limited and/or low-quality subsurface data but with potentially high seismic hazard.

Crooked‐line 2D seismic reflection imaging in crystalline terrains: Part 1, data processing

Geophysics ◽  
2003 ◽  
Vol 68 (1) ◽  
pp. 274-285 ◽  
Author(s):  
Mladen R. Nedimović ◽  
Gordon F. West
Keyword(s):  
Seismic Reflection ◽  
Structural Information ◽  
Imaging Procedures ◽  
Seismic Section ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Processing Line ◽  
Successful Removal ◽  
2D Imaging ◽  
Signal Alignment

For cost and access reasons, most of the seismic reflection data collected in crystalline terrains have been acquired by 2D crooked‐line profiling. When the survey geometry is significantly irregular and the geologic structures have cross‐profile dip, several standard 2D imaging procedures severely underperform. As a result, reflection signal is poorly aligned across individual common midpoint (CMP) gathers, and much is lost during the CMP stack. To improve imaging, either the methods used to align signal before stack need to be modified or more tolerant methods of combining trace signals than the standard CMP stack need to be applied. Because a high‐fold 2D crooked‐line profile is really a 3D survey of a swath of terrain around the processing line, better signal alignment before CMP stacking may be achieved by revisiting the traveltime equation and including the cross‐dip terms into the moveout calculations. Therefore, in addition to the correction of NMO and in‐line dip moveout (DMO), we also locally compute and subsequently remove cross‐dip moveout (CDMO). This requires a procedure for estimating the amount of cross‐dip associated with each local reflection event. Stacking after the successful removal of the CDMO yields what we call an optimum cross‐dip stack—a seismic section that is significantly more complete and informative than the standard stack. Alternatively, amplitude stacking appears to be more robust to residual time anomalies. When little or no cross‐dip information can be extracted from the 2D crooked‐line data, we use it as a last resort to obtain a section that contains more structural information than the standard stack.

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