Academic literature on the topic 'Bottom simulating reflection or BSR'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Bottom simulating reflection or BSR.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Bottom simulating reflection or BSR"
1
Bedle, Heather. "Seismic attribute enhancement of weak and discontinuous gas hydrate bottom-simulating reflectors in the Pegasus Basin, New Zealand." Interpretation 7, no. 3 (2019): SG11—SG22. http://dx.doi.org/10.1190/int-2018-0222.1.
Full textAbstract:
Gas hydrates in the oceanic subsurface are often difficult to image with reflection seismic data, particularly when the strata run parallel to the seafloor and in regions that lack the presence of a bottom-simulating reflector (BSR). To address and understand these imaging complications, rock-physics modeling and seismic attribute analysis are performed on modern 2D lines in the Pegasus Basin in New Zealand, where the BSR is not continuously imaged. Based on rock-physics and seismic analyses, several seismic attribute methods identify weak BSR reflections, with the far-angle stack data being particularly effective. Rock modeling results demonstrate that far-offset seismic data are critical in improving the imaging and interpretation of the base of the gas hydrate stability zone. The rock-physics modeling results are applied to the Pegasus 2009 2D data set that reveals a very weak seismic reflection at the base of the hydrates in the far-angle stack. This often-discontinuous reflection is significantly weaker in amplitude than typical BSRs associated with hydrates. These weak far-angle stack BSRs often do not appear clearly in full stack data, the most commonly interpreted seismic data type. Additional amplitude variation with angle (AVA) attribute analyses provide insight into identifying the presence of gas hydrates in regions lacking a strong BSR. Although dozens of seismic attributes were investigated for their ability to reveal weak reflections at the base of the gas hydrate stability zone, those that enhance class 2 AVA anomalies were most effective, particularly the seismic fluid factor attribute.
2
Vargas-Cordero, I., U. Tinivella, F. Accaino, et al. "Basal and Frontal Accretion Processes versus BSR Characteristics along the Chilean Margin." Journal of Geological Research 2011 (September 12, 2011): 1–10. http://dx.doi.org/10.1155/2011/846101.
Full textAbstract:
Multichannel seismic reflection data recorded between Itata (36°S) and Coyhaique offshores (43°S) were processed to obtain seismic images. Analysis of the seismic profiles revealed that weak and discontinuous bottom simulating reflectors were associated to basal accretion processes, while strong and continuous bottom simulating reflectors were associated to frontal accretion processes. This can be explained considering that during basal accretion processes, extensional tectonic movements due to uplifting can favour fluid escapes giving origin to weaker and most discontinuous bottom simulating reflectors. During frontal accretion processes (folding and thrusting), high fluid circulation and stable tectonic conditions however can be responsible of stronger and most continuous bottom simulating reflectors. Along the Arauco-Valdivia offshores, steep accretionary prisms, normal faults, slope basins, and thicker underplated sediment bed were associated to basal accretion, while along the Itata, Chiloe and Coyhaique offshores, small accretionary prisms, folding, and thinner underplated sediment bed were associated to frontal accretion.
3
Gehrmann, Romina, Christian Müller, Peter Schikowsky, Thomas Henke, Michael Schnabel, and Christian Bönnemann. "Model-Based Identification of the Base of the Gas Hydrate Stability Zone in Multichannel Reflection Seismic Data, Offshore Costa Rica." International Journal of Geophysics 2009 (2009): 1–12. http://dx.doi.org/10.1155/2009/812713.
Full textAbstract:
Along the pacific margin offshore Costa Rica the Bottom Simulating Reflector (BSR) shows a patchy occurrence in 2-D seismic reflection profiles. The reason for this can be either lack of free gas beneath parts of the gas hydrate stability zone (GHSZ) or poor seismic imaging. We compare far to near offset stacked common midpoint sections to reduce imaging ambiguity utilizing the amplitude variation with offset effect and thus successfully distinguish BSRs from regular sediment reflections. In combination with 1-D modeling of the base of the GHSZ we disqualify or qualify reflections in the predicted depth range as BSR. Additionally we calculate the heat flow and compare it with an analytical solution to detect thermal anomalies, for example, at the frontal prism. The higher confidence in BSR depths based on the far offset stacks and heat flow calculations allows further analyses on gas hydrate concentration estimates and tectonic evolution of the margin.
4
Aguiar, Laisa da Fonseca, Antonio Fernando Menezes Freire, Luiz Alberto Santos, et al. "ANALYSIS OF SEISMIC ATTRIBUTES TO RECOGNIZE BOTTOM SIMULATING REFLECTORS IN THE FOZ DO AMAZONAS BASIN, NORTHERN BRAZIL." Brazilian Journal of Geophysics 37, no. 1 (2019): 43. http://dx.doi.org/10.22564/rbgf.v37i1.1988.
Full textAbstract:
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.
5
Liang, Jinqiang, Zijian Zhang, Pibo Su, Zhibin Sha, and Shengxiong Yang. "Evaluation of gas hydrate-bearing sediments below the conventional bottom-simulating reflection on the northern slope of the South China Sea." Interpretation 5, no. 3 (2017): SM61—SM74. http://dx.doi.org/10.1190/int-2016-0219.1.
Full textAbstract:
The continuous bottom-simulating reflection (BSR) is commonly considered to mark the base of gas hydrate stability zone. Below this depth, gas hydrate gives away to free gas or water filling with pore spaces of sediments. We integrated and analyzed seismic data collected in 2008, and logging-while-drilling (LWD) data and coring results acquired by the Fugro Voyager in 2015 in the Shenhu area on the northern slope of the South China Sea. Based on seismic and well-log correlation, a BSR with typical characteristics of gas hydrates and free gas was identified at 237 m, below the mudline (BML). However, LWD data reveal a 63 m thick hydrate layer from 205 to 268 m BML. Increases in resistivity and velocity at 262 m BML indicate that gas hydrate is likely presented below the BSR. The observed pore-water freshening with depth and infrared image of core samples are consistent with geophysical interpretation. Seismic and well interpretations reveal continuous, discontinuous, and pluming BSRs in the Shenhu area. The continuous BSR indicates the base of the methane gas hydrate stability zone, and structure II gas hydrate is likely presented below the BSR. Deep thermogenic fluid locally entrapped within shallow-buried sediments may reinforce gas-hydrate accumulations near the discontinuous and pluming BSRs. We conclude that seismic responses of structure II gas hydrate can be distinct from structure I gas hydrate. Understanding the seismic characterizations of structures I and II will help in the evaluation of gas-hydrate reservoirs and inferring the presence of deep thermogenic reservoirs.
6
Li, Shou Jun, Feng You Chu, Yin Xia Fang, and Zi Yin Wu. "Associated Interpretation of Sub-Bottom and Single-Channel Seismic Profiles from Shenhu Area in the North Slope of South China Sea - Characteristic of Gas Hydrate Sediment." Advanced Materials Research 217-218 (March 2011): 1430–37. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.1430.
Full textAbstract:
Abstract：The study area of this paper is the slope of Shenhu Area in the northern South China Sea. We interpreted both sub-bottom and single-channel seismic profiles to describe the acoustic characteristic of gas hydrate sediment and to discuss the cause of its formation. We distinguished some abnormal physiognomy and geologic objects that are relative to gas hydrate in profiles. Protuberance, shallow fault, acoustic blank patch, partial enhanced reflection and acoustic blank zone were discovered in the legible sub-bottom profile. The shallow gassy belt locates under the seabed from 34 to 82 m. Contrasting the sub-bottom profile with the data of Chinese first gas hydrate expedition, we believed that the gas in the shallow gassy belt came from the decompounding of gas hydrate in deep stratum. Pockmark, seepage, fold and Bottom Simulating Reflector (BSR) were recognized in the single-channel seismic profile. The depth of BSR is slightly deeper than that of the samples of Chinese first gas hydrate expedition in the study area. We think the BSR in the seismic profile may be the bottom of gas hydrate. Based on the time-depth conversion, we plotted out Oligocene, early Miocene, middle Miocene and Pliocene in the seismic profile according to the sedimentary thickness, sedimentary rate and age of ODP site 1148 and set up the chronology of the gas hydrate sediment.
7
Luo, Yi, and Xin Su. "The Double (or Multiple) BSRs Observations and their Tentative Interpretations." Advanced Materials Research 734-737 (August 2013): 467–75. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.467.
Full textAbstract:
Gas hydrate is a solid ice-like compound and is stable at low temperature and high pressure conditions found beneath permafrost and in marine sediments on continental margins offshore. In the marine environment, the bottom-simulating reflector (BSR) in seismic reflection profiles is interpreted to indicate the base of the gas hydrate stability zone (GHSZ).In many locations two or more sub-parallel BSRs have been reported. We not only compared the BSRs characteristics from reported areas but also discussed the mechanism of GHSZ shifts by climate change, sedimentation process and tectonic movement. We also considered the mix gases composition hydrate stability in certain marine environment and gave a simple model for the BSR differences on water depth.
8
Collins, Barclay P., and Joel S. Watkins. "Analysis of a gas hydrate off southwest Mexico using seismic processing techniques and Deep Sea Drilling Project Leg 66 results." GEOPHYSICS 50, no. 1 (1985): 16–24. http://dx.doi.org/10.1190/1.1441830.
Full textAbstract:
Analysis of a reprocessed seismic reflection line and results from Deep Sea Drilling Project Leg 66 off the southwest coast of Mexico reveal a bottom simulating reflector (BSR) associated with the equilibrium phase boundary of methane hydrate. Several seismic processing techniques were used to accentuate the lateral continuity of the BSR and to delineate the top and base of a 200-700 m thick concentrated hydrate layer. These results suggest the concentrated hydrate layer extends about 20 km parallel to the slope of the inner trench wall in water depths ranging from 2 250-4 500 m. Direct seismic indicators below the BSR and geochemical evidence imply small amounts of free gas may be trapped beneath the base of the hydrate layer and suggest that low‐permeability hydrated sediments can act as a seal for reservoirs.
9
Satyavani, N., and Kalachand Sain. "Seismic Insights into Bottom Simulating Reflection (BSR) in the Krishna-Godavari Basin, Eastern Margin of India." Marine Georesources & Geotechnology 33, no. 3 (2014): 191–201. http://dx.doi.org/10.1080/1064119x.2013.797059.
Full text
10
Mayasari, Vanniastuti, Okto Ivansyah, and Yulinar Firdaus. "Identifikasi Keberadaan Gas Hidrat Menggunakan Bottom Simulating Reflector pada Penampang Seismic 2D di Cekungan Aru, Papua Barat." POSITRON 9, no. 2 (2019): 61. http://dx.doi.org/10.26418/positron.v9i2.33303.
Full textAbstract:
Gas hidrat merupakan senyawa dengan molekul gas terperangkap di dalam sel-sel kristal yang terbentuk dari molekul air dan dipertahankan dalam bentuk hidrat oleh ikatan hidrogen. Gas hidrat diharapkan dapat menjadi sumber energi alternatif. Penelitian ini dilakukan di Cekungan Aru, Papua Barat. Cekungan Aru memiliki kondisi terisi oleh sedimen berupa fraksi halus setelah proses deformasi pada masa pliosen hingga resen yang diidentifikasi sebagai sedimen terigenus atau pelagik karena terdiri dari sisa-sisa cangkang mikroorganisme sehingga memungkinkan terbentuknya zona stabilitas gas hidrat. Penelitian ini bertujuan untuk mengidentifikasi keberadaan gas hidrat menggunakan bottom simulating reflector (BSR) pada penampang seismik 2D. Kenampakan BSR menjadi indikator utama keberadaan gas hidrat pada saat proses interpretasi. Penelitian ini menggunakan tiga lintasan seismik hasil brute stack, yaitu L01.6, L26, dan L27. Berdasarkan hasil penelitian yang diperoleh, BSR terindikasi pada L01.6 dengan rentang CDP 8321 hingga CDP 8481 pada TWT 4000 ms hingga TWT 5500 ms, kemudian CDP 16300 hingga CDP 23600 pada TWT 4500 ms hingga TWT 7900 ms dan L27 dengan rentang CDP 1281 hingga CDP 4641 pada TWT 5250 ms hingga TWT 6500 ms. Kenampakan BSR pada penampang seismik menyerupai garis putus-putus, memotong stratigrafi, sejajar dengan lapisan sedimen, dan ada yang membentuk lensa-lensa. Karakteristik BSR juga didukung dengan anomali interval velocity pada semblance saat proses analisis kecepatan.
Dissertations / Theses on the topic "Bottom simulating reflection or BSR"
1
Le, Anh. "Stratigraphic evolution and plumbing system of the Cameroon margin, West Africa." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/stratigraphic-evolution-and-plumbing-system-of-the-cameroon-margin-west-africa(94a13f64-a927-47b6-b456-a0b57c0e5494).html.
Full textAbstract:
The Kribi-Campo sub-basin is the northernmost of a series of Aptian basins along the coast of West Africa. These extensional basins developed as a result of the northward progressive rifting of South America from West Africa, initiated c. 130 Ma ago. Post-rift sediments of the Kribi-Campo sub -basin contain several regional unconformities and changes in basin-fill architecture that record regional tectonic events. The tectono-stratigraphic evolution and plumbing system has been investigated using a high-quality 3D seismic reflection dataset acquired to image the deep-water Cretaceous-to-Present-day post-rift sediments. The study area is located c. 40 km offshore Cameroon in 600 to 2000 m present-day water depth, with full 3D seismic coverage of 1500 km2, extending down to 6.5 seconds Two-Way Travel time. In the late Cretaceous the basin developed as a result of tectonism related to movement of the Kribi Fracture Zone (KFZ), which reactivated in the late Albian and early Senonian. This led to inversion of the early syn-rift section overlying the KFZ to the southeast. Two main fault-sets - N30 and N120 - developed in the center and south of the basin. These normal faults propagated from the syn-rift sequences: the N120 faults die out in the early post-rift sequence (Albian time) whilst N30 faults tend to be associated with the development of a number of fault-related folds in the late Cretaceous post-rift sequence, and have a significant control on later deposition. The basin is filled by Upper Cretaceous to Recent sediments that onlap the margin. Seismic facies analysis and correlation to analogue sections suggest the fill is predominantly fine-grained sediments. The interval also contains discrete large scale channels and fans whose location and geometry were controlled by the KFZ and fault-related folds. These are interpreted to contain coarser clastics. Subsequently, during the Cenozoic, the basin experienced several tectonic events caused by reactivation of the KFZ. During the Cenozoic, deposition was characterized by Mass Transport Complexes (MTCs), polygonal faulting, channels, fans and fan-lobes, and aggradational gullies. The main sediment feeder systems were, at various times, from the east, southeast and northeast. The plumbing system shows the effects of an interplay of stratigraphic and structural elements that control fluid flow in the subsurface. Evidence for effective fluid migration includes the occurrence of widespread gas-hydrate-related Bottom Simulating Reflections (BSRs) 104 - 250 m below the seabed (covering an area of c. 350 km2, in water depths of 940 m - 1750 m), pipes and pockmarks. Focused fluid flow pathways have been mapped and observed to root from two fan-lobe systems in the Mid-Miocene and Pliocene stratigraphic intervals. They terminate near, or on, the modern seafloor. It is interpreted that overpressure occurred following hydrocarbon generation, either sourced from biogenic degradation of shallow organic rich mudstone, or from effective migration from a thermally mature source rock at depth. This latter supports the possibility also of hydrocarbon charged reservoirs at depth. Theoretical thermal and pressure conditions for gas hydrate stability provide an opportunity to estimate the shallow geothermal gradient. Variations in the BSR indicate an active plumbing system and local thermal gradient anomalies are detected within gullies and along vertically stacked channels or pipes. The shallow subsurface thermal gradient is calculated to be 0.052 oC m-1. With future drilling planned in the basin, this study also documents potential drilling hazards in the form of shallow gas and possible remobilised sands linked with interconnected and steeply dipping sand bodies.
2
Boukongo, Sotaine Marie Aimé. "Etude des hydrates de gaz sur la marge active de Nankai (Japon) : analyse de données de sismique réflexion 3D et inversion des formes d'onde." Paris, Institut de physique du globe, 2007. http://www.theses.fr/2007GLOB0002.
Full textAbstract:
L'analyse de données de sismique réflexion 3D sur la marge active de Nankai (Japon) a permisde mettre en évidence le BSR (bottom simulating reflector) et le double BSR. Le BSR est un contrastedimpédance acoustique à linterface séparant les sédiments riches en hydrates de gaz de forte vitesseau dessus et les sédiments riches en gaz libre en dessous. Le double BSR peut être considéré commeun BSR fossile ou résultant d'un mélange dans les sédiments des gaz de composition différente. LeBSR est par suite utilisé pour contraindre le régime thermique dans la boîte 3D (5km x 42. 5 km) de lamarge de Nankai. Le flux de chaleur calculé à partir des profondeurs du BSR donne des valeurscomprises entre 20-68 mW/m2. Des fortes amplitudes de BSR sont localisées dans les zones où le fluxde chaleur est relativement faible, et des faibles amplitudes du BSR sont par contre localisées dans leszones où le flux de chaleur est relativement important. La circulation des fluides chauds perturberaitl'amplitude du BSR. Par ailleurs, le BSR est absent au voisinage de la faille de Tokai dans la zone dubassin de pente, et est discontinu tantôt absent au niveau de la faille de Kodaiba dans la zone du bassindavant-arc. Dans la zone du bassin davant-arc où la distribution du BSR est plus importante, lesrésultats de linversion des formes d'onde ont permis de confirmer la présence des zones à fortevitesse (en rapport avec les hydrates de méthane) au dessus du BSR et des zones à faible vitesse (enrapport avec le gaz libre) en dessous du BSR. La présence du gaz libre sous jacent augmenteraitl'amplitude du BSR. La concentration des hydrates de méthane estimée est inférieure à 25 %. Levolume moyen des hydrates de gaz calculé est de 0. 85 km3. La concentration du gaz libre varie entre0. 7 et 8 %. Le volume moyen du gaz libre calculé est de 0. 06 km3. Au regard de la superficie de lazone étudiée, on conclut que ces concentrations/volumes sont énormes mais, ne peuvent constituer unréservoir économiquement exploitable, car les hydrates de gaz sont disséminés dans les sédiments<br>The analysis of 3D seismic reflection data on the Nankai (Japan) active margin showed evidenceof a BSR (bottom simulating reflector) and a double BSR. The BSR is an acoustic impedance contrastat the interface separating sediments rich in gas hydrate, having a high velocity above, and sedimentsrich in free gas, having a low velocity below. The double BSR can be considered as a fossil BSR orcan result from a mixture of gases of different compositions within the sediments. The BSR depth isused to constrain the thermal regime in the 3D box (5 km x 42. 5 km) of the Nankai margin. The heatflow calculated from BSR depths gives values between 20-68 mW/m2. Strong BSR amplitudes arelocalized in the zone where the heat flow is relatively low, and weak BSR amplitudes are localized inthe zone where the heat flow is relatively high. The circulation of warm fluids would perturb theamplitude of BSR. The BSR is absent around the Tokai fault in the slope basin zone, and issometimes discontinuous or absent around the Kodaiba fault in the forearc basin zone. In the forearcbasin where the distribution of the BSR is more important, full waveform inversion results allowed toconfirm the presence of a zone with high velocity above the BSR, which could be due to the presenceof gas hydrate in sediments. Just below the BSR, we find a low velocity zone, which could be due tothe presence of the free gas in sediments. Strong BSR amplitude could be correlated with the presenceof underlaying free gas. The estimated concentration of gas hydrate is lower than 25 %. The meanvolume of gas hydrate calculated is about 85 x 107 m3. The estimated concentration of free gas variesbetween 0. 7 and 8 %. The mean volume of free gas calculated is about 6 x 107 m3. In the study area,we conclude that these concentrations/volumes are enormous but, they cannot constitute aneconomically exploitable reservoir, because gas hydrates are disseminated in the sediments
3
Lewis, Dan'L 1986. "Salt Tectonics and Its Effect on Sediment Structure and Gas Hydrate Occurrence in the Northwestern Gulf of Mexico from 2-D Multichannel Seismic Data." Thesis, 2012. http://hdl.handle.net/1969.1/148130.
Full textAbstract:
This study was undertaken to investigate mobile salt and its effect on fault structures and gas hydrate occurrence in the northwestern Gulf of Mexico. Industry 2-D multichannel seismic data were used to investigate the effects of the salt within an area of 7,577 mi^2 (19,825 km^2) on the Texas continental slope in the northwestern Gulf of Mexico. The western half of the study area is characterized by a thick sedimentary wedge and isolated salt diapirs whereas the eastern half is characterized by a massive and nearly continuous salt sheet topped by a thin sedimentary section. This difference in salt characteristics marks the edge of the continuous salt sheets of the central Gulf of Mexico and is likely a result of westward decline of original salt volume. Beneath the sedimentary wedge in the western part of the survey, an anomalous sedimentary package was found, that is described here as the diapiric, gassy sediment package (DGSP). The DGSP is highly folded at the top and is marked by tall, diapiric features. It may be either deformed shale or the toe of a complex thrust zone detaching the sedimentary wedge from deeper layers. The dataset was searched for the occurrence of bottom simulating reflectors (BSRs), as they are widely accepted as a geophysical indicator of gas trapped beneath gas hydrate deposits, which are known to occur farther east in the Gulf. Although, many seismic signatures were found that suggest widespread occurrence of gas within the upper sediment column, few BSRs were found. Even considering non-traditional definitions of BSRs, only a few occurrences of patchy and isolated BSRs features were identified. The lack of traditional BSRs is likely the result of geologic conditions that make it difficult to recognize gas hydrate deposits. These factors include: (1) unfavorable layer geometries, (2) flow of warm brines from depth, (3) elevated geotherms due to the thermogenic properties of salt and its varying thickness, and (4) widespread low porosity and permeability sediments within the gas hydrate stability zone.
4
Haacke, R. Ross, Graham K. Westbrook, and Roy D. Hyndman. "FORMATION OF THE BOTTOM-SIMULATING REFLECTOR AND ITS LINK TO VERTICAL FLUID FLOW." 2008. http://hdl.handle.net/2429/1050.
Full textAbstract:
Many places where natural gas hydrate occurs have a regionally extensive, bottom-simulating seismic
reflector (BSR) at the base of the gas hydrate stability zone (GHSZ). This reflection marks the top of an
underlying free-gas zone (FGZ). Usually, hydrate recycling (that produces gas as the stability field moves
upward relative to sediments) is invoked to explain the presence and properties of the sub-BSR FGZ.
However, this explanation is not always adequate: FGZs are often thicker in passive-margin environments
where hydrate recycling is relatively slow, than in convergent-margin environments where hydrate
recycling is relatively fast (e.g. Blake Ridge compared with Cascadia). Furthermore, some areas with thick
FGZs and extensive BSRs (e.g. west Svalbard) have similar rates of hydrate recycling to northern Gulf or
Mexico, yet the latter has no regional BSR.
Here we discuss a gas-forming mechanism that operates in addition to hydrate recycling, and which
produces a widespread, regional, BSR when gas is transported upward through the liquid phase; this
mechanism is dominant in tectonically passive margins. If the gas-water solubility decreases downward
beneath the GHSZ (this occurs where the geothermal gradient and the pressure are relatively high), low
rates of upward fluid flow enable pore water to become saturated in a thick layer beneath the GHSZ. The
FGZ that this produces achieves a steady-state thickness that is primarily sensitive to the rate of upward
fluid flow. Consequently, geophysical observations that constrain the thickness of sub-BSR FGZs can be
used to estimate the regional, diffuse, upward fluid flux through natural gas-hydrate systems.
5
Yelisetti, Subbarao. "Seismic structure, gas hydrate, and slumping studies on the Northern Cascadia margin using multiple migration and full waveform inversion of OBS and MCS data." Thesis, 2014. http://hdl.handle.net/1828/5719.
Full textAbstract:
The primary focus of this thesis is to examine the detailed seismic structure of the
northern Cascadia margin, including the Cascadia basin, the deformation front and
the continental shelf. The results of this study are contributing towards understanding
sediment deformation and tectonics on this margin. They also have important
implications for exploration of hydrocarbons (oil and gas) and natural hazards (submarine landslides, earthquakes, tsunamis, and climate change).
The first part of this thesis focuses on the role of gas hydrate in slope failure observed
from multibeam bathymetry data on a frontal ridge near the deformation front
off Vancouver Island margin using active-source ocean bottom seismometer (OBS)
data collected in 2010. Volume estimates (∼ 0.33 km^3) of the slides observed on this
margin indicate that these are capable of generating large (∼ 1 − 2 m) tsunamis.
Velocity models from travel time inversion of wide angle reflections and refractions
recorded on OBSs and vertical incidence single channel seismic (SCS) data were used
to estimate gas hydrate concentrations using effective medium modeling. Results indicate a shallow high velocity hydrate layer with a velocity of 2.0 − 2.1 km/s that
corresponds to a hydrate concentration of 40% at a depth of 100 m, and a bottom
simulating reflector (BSR) at a depth of 265 − 275 m beneath the seafloor (mbsf).
These are comparable to drilling results on an adjacent frontal ridge. Margin perpendicular normal faults that extend down to BSR depth were also observed on SCS
and bathymetric data, two of which coincide with the sidewalls of the slump indicating
that the lateral extent of the slump is controlled by these faults. Analysis of
bathymetric data indicates, for the first time, that the glide plane occurs at the same
depth as the shallow high velocity layer (100±10 mbsf). In contrast, the glide plane
coincides with the depth of the BSR on an adjacent frontal ridge. In either case, our
results suggest that the contrast in sediments strengthened by hydrates and overlying
or underlying sediments where there is no hydrate is what causing the slope failure
on this margin.
The second part of this dissertation focuses on obtaining the detailed structure
of the Cascadia basin and frontal ridge region using mirror imaging of few widely
spaced OBS data. Using only a small airgun source (120 cu. in.), our results indicate
structures that were previously not observed on the northern Cascadia margin. Specifically, OBS migration results show dual-vergence structure, which could be related to horizontal compression associated with subduction and low basal shear stress resulting from over-pressure. Understanding the physical and mechanical properties of the basal layer has important implications for understanding earthquakes on this margin.
The OBS migrated image also clearly shows the continuity of reflectors which enabled
the identification of thrust faults, and also shows the top of the igneous oceanic crust
at 5−6 km beneath the seafloor, which were not possible to identify in single-channel
and low-fold multi-channel seismic (MCS) data.
The last part of this thesis focuses on obtaining detailed seismic structure of the
Vancouver Island continental shelf from MCS data using frequency domain viscoacoustic
full waveform inversion, which is first of its kind on this margin. Anelastic
velocity and attenuation models, derived in this study to subseafloor depths of ∼ 2
km, are useful in understanding the deformation within the Tofino basin sediments,
the nature of basement structures and their relationship with underlying accreted
terranes such as the Crescent and the Pacific Rim terranes. Specifically, our results
indicate a low-velocity zone (LVZ) with a contrast of 200 m/s within the Tofino basin
sediment section at a depth 600 − 1000 mbsf over a lateral distance of 10 km. This
LVZ is associated with high attenuation values (0.015 − 0.02) and could be a result
of over pressured sediments or lithology changes associated with a high porosity layer
in this potential hydrocarbon environment. Shallow high velocities of 4 − 5 km/s
are observed in the mid-shelf region at depths > 1.5 km, which is interpreted as
the shallowest occurrence of the Eocene volcanic Crescent terrane. The sediment
velocities sharply increase about 10 km west of Vancouver Island, which probably
corresponds to the underlying transition to the Mesozoic marine sedimentary Pacific
Rim terrane. High attenuation values of 0.03 − 0.06 are observed at depths > 1 km,
which probably corresponds to increased clay content and the presence of mineralized
fluids.<br>Graduate<br>0373<br>0372<br>0605<br>subbarao@uvic.ca
6
Mosher, David C. "BOTTOM SIMULATING REFLECTORS ON CANADA?S EAST COAST MARGIN: EVIDENCE FOR GAS HYDRATE." 2008. http://hdl.handle.net/2429/1044.
Full textAbstract:
The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated
stability zone calculations, but the physical evidence is yet to be discovered. While geophysical
evidence derived from seismic and borehole logging data provides indications of hydrate occurrence
in a number of areas, the results are not regionally comprehensive and, in some cases, are
inconsistent. In this study, the results of systematic seismic mapping along the Scotian and
Newfoundland margins are documented. An extensive set of 2-D and 3-D, single and multi-channel,
seismic reflection data comprising ~45,000 line-km was analyzed for possible evidence of hydrate.
Bottom simulating reflectors (including one double BSR) were identified at five different sites,
ranging between 300 and 600 m below the seafloor and in water depths of 1000 to 2900 m. The
combined area of the five BSRs is 1720 km2, which comprises a small proportion of the theoretical
stability zone area along the Scotian and Newfoundland margins (~635,000 km2). The apparent
paucity of BSRs may relate to the rarity of gas hydrates on the margin or may be simply due to
geophysical limitations in detecting hydrate.
Book chapters on the topic "Bottom simulating reflection or BSR"
1
Mienert, Jürgen, and Stefan Bünz. "Bottom Simulating Seismic Reflectors (BSR)." In Encyclopedia of Marine Geosciences. Springer Netherlands, 2016. http://dx.doi.org/10.1007/978-94-007-6238-1_133.
Full text
2
Bangs, N. L. B., D. S. Sawyer, and X. Golovchenko. "The Cause of the Bottom-Simulating Reflection in the Vicinity of the Chile Triple Junction." In Proceedings of the Ocean Drilling Program, 141 Scientific Results. Ocean Drilling Program, 1995. http://dx.doi.org/10.2973/odp.proc.sr.141.026.1995.
Full text
3
"Seismic and Thermal Characterization of a Bottom-simulating Reflection in the Northern Gulf of Mexico." In Natural Gas Hydrates—Energy Resource Potential and Associated Geologic Hazards. American Association of Petroleum Geologists, 2009. http://dx.doi.org/10.1306/13201146m893343.
Full text
4
"Variation of Bottom-simulating-reflection Strength in a High-flux Methane Province, Hikurangi Margin, New Zealand." In Natural Gas Hydrates—Energy Resource Potential and Associated Geologic Hazards. American Association of Petroleum Geologists, 2009. http://dx.doi.org/10.1306/13201159m893356.
Full text
5
"Structural Controls on the Formation of Bottom-simulating Reflectors Offshore Southwestern Taiwan from a Dense Seismic Reflection Survey." In Natural Gas Hydrates—Energy Resource Potential and Associated Geologic Hazards. American Association of Petroleum Geologists, 2009. http://dx.doi.org/10.1306/13201160m893357.
Full text
6
Bangs, N. L., and K. M. Brown. "Regional Heat Flow in the Vicinity of the Chile Triple Junction Constrained by the Depth of the Bottom-Simulating Reflection." In Proceedings of the Ocean Drilling Program, 141 Scientific Results. Ocean Drilling Program, 1995. http://dx.doi.org/10.2973/odp.proc.sr.141.043.1995.
Full textConference papers on the topic "Bottom simulating reflection or BSR"
1
Pevzner, R. L., A. L. Volkonskaya, S. V. Bouriak, A. A. Bocharova, and V. N. Blinova. "Using the Dynamics of Bottom Simulating Reflector (BSR) for Prediction of Gas Hydrate Content in Marine Sediments." In Saint Petersburg 2008. EAGE Publications BV, 2008. http://dx.doi.org/10.3997/2214-4609.20146805.
Full text
2
Yamazaki, Tetsuo, Daisuke Monoe, Tomoaki Oomi, Kisaburo Nakata, and Tomohiko Fukushima. "Application of Methane Supply Process Unit in Mass Balance Ecosystem Model Around Cold Seepage." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57498.
Full textAbstract:
Natural cold seepages are characterized as rapid upward transports of methane from deeper parts of geological structures to the seafloor. The original methane supply source is expected to locate below BSR (Bottom Simulating Reflector). The methane moved up to seafloor is mainly consumed by microorganisms living in anoxic marine sediments. When the methane supply is very large or rapid, remaining unconsumed methane escapes into the water column and is consumed by oxidizing bacteria. The supply mechanism of methane from the supply source to the cold seepages has not yet being clarified. In order to integrate the methane consumption processes in sediments and water column, a simple methane supply mechanism is developed.
3
Grion, Sergio, Gualtiero Böhm, Giuliana Rossi, Umberta Tinivella, and Alfredo Mazzotti. "Tomographic and AVO analyses of Bottom Simulating Reflectors (BSR) on real data." In SEG Technical Program Expanded Abstracts 1997. Society of Exploration Geophysicists, 1997. http://dx.doi.org/10.1190/1.1885763.
Full text
4
Shu, Xiejun, Senhui Jiang, and Ruijie Li. "Numerical Simulation of Engineering Wave for Zhongzui Bay." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29504.
Full textAbstract:
For providing a better shelter condition, it is necessary to build a breakwater in Zhongzui Bay. In order to know whether mooring area meets the requirement after engineering construction and compare the mooring area between solid breakwater and permeable breakwater, a numerical simulation method is used in the sheltering harbor of Zhongzui Bay. The used Mild-slope equation which describes wave refraction, diffraction and reflection, considers the steep slope bottom and effect of energy dissipation. It has been validated to fit for simulating wave transformation in the coastal zone. Under extreme high water level and design high water level, wave fields in the calculation area of three wave types in three different return periods are simulated by using this method respectively. In addition, wave height in front of breakwater can be provided. Then the wave parameters and the mooring area of two occasions, with and without breakwater, are gained in calculation area. Based on these results, some conclusions are presented in the end.