Seistec Seismic Profiles: A Tool to Differentiate Gas Signatures

Baltzer, Agnès; Tessier, Bernadette; Nouzé, Hervé; Bates, Richard; Moore, Colin; Menier, David

doi:10.1007/s11001-005-3721-x

Cited by 42 publications

(39 citation statements)

References 12 publications

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“…Following the classifications of Taylor (1992) and Baltzer et al (2005), it was possible to identify acoustic signatures of black shadow and acoustic blanket. Features related to percolation of gas as intra sedimentary plumes, turbidity pinnacle, and structures related to seepages to the water column, as acoustic plumes and pockmarks were also identified.…”

Section: Acoustic Signatures and Core Sediment Propertiesmentioning

confidence: 99%

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High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

et al. 2016

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. High-resolution acoustic mapping of gas charged sediments and living benthic foraminifera assemblages from the NE region of the Guanabara Bay (RJ, Brazil). Journal of Sedimentary Environments, 1 (3): 360-384. AbstractThis work was performed in the NE region of the Guanabara Bay, a highly impacted Brazilian coastal system, located in Rio de Janeiro State. It aimed to: i) identify and map the areas with occurrence of gas in the sediment, as well as its acoustic signature; ii) characterize the physical properties of the sediments and; iii) document the response of microbenthic organisms (living benthic foraminifera) to changes in quantity and quality of organic matter. Seismic surveys at the frequency of 12 kHz identified a large area with about 50% gas charged sediments in the study area.The main acoustic signatures of the shallow gas were black shadow and gas blanket. In addition, features related to gas seepages to the water column (acoustic plumes and pockmarks) and gas percolation within the sediments (intrasedimentary plumes, turbidity pinnacles) were also identified. The gas has a biogenic origin and results from the high acumulation rate between 0.03 to 0.9 cm.year -1 and from the decomposition of large amount of organic matter (10-20%). Vertical distribution of gas ranges from few centimeters to 9 m below the water-sediments interface. These occurrences are related to both gas migration from lower sedimentary layers to Holocene muds above, and to recent generation in near-surface sediments as the area display favorable conditions for gas production. Cores ranging from 150-240 cm in length have predominantly muddy sediments and variations in the P-wave velocity followed the changes in sediment density, controlled mainly by the presence of gas in sediments, bioclasts accumulation, textural variation and percentage of organic matter. Journal of Sedimentary Environments

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Section: Acoustic Signatures and Core Sediment Propertiesmentioning

confidence: 99%

“…Depending on their seismic character, size and geometry, various descriptive features have been used for gas charged sediments, such as acoustic blanket, black shadow, plumes, curtain, and acoustic turbidity (Taylor, 1992;Yun et al, 1999;Garcia-Gil et al, 2002;Baltzer et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

et al. 2016

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“…The shallow gas features were defined in accordance with their shape and echo-character; in the shallow seismic high resolution record the works of GARCIA-GIL et al (2002), LEE et al (2005, BALTZER et al (2005), and TAYLOR (1992) among others were used as reference. The depth of the gas features was measured in milliseconds (ms) and the sound velocity used was 1500 m/s, so it is possible to estimate the depths of the features in meters.…”

Section: Methodsmentioning

confidence: 99%

“…Acoustic Plumes consisting of a series of parabolic high amplitude reflections occur frequently along the seismic line, typically every 100-200 meters (TAYLOR, 1992). Besides, Black Shadows (Figure 3), features that are different from gas curtains in that they permit the acoustic seabed to be reached, are present (BALTZER et al, 2005). Seepages were found in 2 profiles on dark blue lines in the south-central and north portions of Figure 3.…”

Section: Conceição Lagoon Gas Structures: Forms and Distributionmentioning

confidence: 99%

“…The formation of these gas structures results from their sedimentary environment, which may be due to recent sedimentation or human activity, among the evolutionary processes responsible for the characterization of the sedimentary deposition environment (GARCIA-GIL et al, 2002;BALTZER et al, 2005). The accumulation of these gases occurred in former geological periods (i.e., thousands of years before the present), due to the intense oxidization of organic matter in a sedimentary environment (GARCIA-GIL et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Shallow gas seismic structures: forms and distribution on Santa Catarina Island, Southern Brazil

et al. 2016

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This paper presents the spatial distribution of shallow gas structures and classifies them on the basis of two different data sets of CHIRP seismic records, one from the Conceição Lagoon (CL) and the other from North Bay (NB), both on Santa Catarina Island, Southern Brazil. Side scan sonar data from the CL were used to facilitate the understanding. The sub bottom (SB) seismic data were processed and interpreted by means of the SeisPrho software, the side scan sonar (SSS) data by SonarWiz5 software and the spatial extension being measured with the help of GIS. The shallow gas structures were defined in accordance with their shapes in the seismic recordings (echo-character). At the CL, shallow gas accumulations were found in the form of seepages and features presenting shallow gas structures between the surface and 8.20 ms (around 12.3 m). Accumulations of gas were found in the form of Acoustic Blanking with Acoustic Plume, and also Black Shadows. Pockmarks were found on the lagoon floor and associated with gas seepages (average size diameter 0.97 ± 0.19 m and density from 54 to 242 units per 50 m2). In the NB three types of shallow gas features were found in the seismic profile, namely Acoustic Blanking, Turbidity Pinnacles and Intra-sedimentary plumes. The depth varied from the surface to 12.10 ms (around 18.15 m). In both environments, the gas is escaping from the sediment into the water column. The Pockmarks in the CL and the Acoustic Plume features and sediment rich in total sulfur in the NB validate these findings.

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Geophysical exploration of an active pockmark field in the Bay of Concarneau, southern Brittany, and implications for resident suspension feeders

et al. 2014

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Seistec Seismic Profiles: A Tool to Differentiate Gas Signatures

Cited by 42 publications

References 12 publications

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

High-Resolution Acoustic Mapping of Gas Charged Sediments and Living Benthic Foraminifera Assemblages From the Ne Region of the Guanabara Bay (Rj, Brazil)

Shallow gas seismic structures: forms and distribution on Santa Catarina Island, Southern Brazil

Geophysical exploration of an active pockmark field in the Bay of Concarneau, southern Brittany, and implications for resident suspension feeders

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