Seismic No-Data Zone, Offshore Mississippi Delta: Part Ii-Using Geologic Information To Predict Acoustic Properties

May, Jeffrey A.; Meeder, Charles A.; Tinkle, Anthony R.; Wener, Kenneth R.

doi:10.4043/5754-ms

Cited by 4 publications

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“…b) which may indicate the absence of shallow refractors followed by high velocity contrast (May et al . ; Yilmaz ). Furthermore, the velocity function from the vertical seismic profiling (VSP) measurement at the well location suggested that the near‐surface velocity may not always increase with depth.…”

Section: Time Domain Seismic Processingmentioning

confidence: 99%

Advanced three‐dimensional seismic imaging of deep supercritical geothermal rocks in Southern Tuscany

Jusri

Bertani

Buske

2019

Geophysical Prospecting

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A B S T R A C TThe seismic K-Horizon is the key to gaining understanding on the deep supercritical geothermal rocks in Southern Tuscany. The K-Horizon is hosted in metamorphic rocks, which cause strong seismic wavefield scattering resulting in a poor signal-to-noise ratio. Our study aims to reveal high-resolution seismic images of the K-Horizon below a geothermal field in Southern Tuscany, using an advanced threedimensional seismic depth imaging approach. The key seismic pre-processing steps in the time domain include muting a large amount of persistent noise based on the statistical analysis of the seismic amplitudes, and tomostatics technique to correct for static effects. We carried out seismic depth imaging using Kirchhoff Pre-Stack Depth Migration and Fresnel Volume Migration techniques. Each migration technique was tested with constant and heterogeneous three-dimensional velocity models. Due to the difficulties in determining emergent angles for this low signal-to-noise ratio data set, the migration results with the heterogeneous three-dimensional velocity model show less coherent reflections compared to the migration results using the constant velocity model. Both velocity models however lead to relatively the same structure and depth of the K-Horizon, indicating the similarity of the average velocities along the wave propagation paths in both velocity models. With both velocity models Fresnel Volume Migration yields the K-Horizon with better reflection coherency and higher signal-to-noise ratio than standard Kirchhoff Pre-Stack Depth Migration. Nevertheless, both migration techniques have been able to reveal the K-Horizon with relatively high resolution and provide a reliable basis for geothermal rock characterization as well as steering of the first geothermal well penetrating the K-Horizon.

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Section: Time Domain Seismic Processingmentioning

confidence: 99%

Advanced three‐dimensional seismic imaging of deep supercritical geothermal rocks in Southern Tuscany

Jusri

Bertani

Buske

2019

Geophysical Prospecting

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Potential distribution of subsurface methane in the sediments of the eastern Arabian Sea and its possible implications

Karisiddaiah¹,

Veerayya²

1996

J. Geophys. Res.

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High-resolution shallow seismic reflection data obtained in the c•mtinental shelf sediments off western India t¾om 10'•q to 22'•q reveal the characteristic ahomalous seismic signatures in the lbrm of acoustic maskings of methane-rich horizons. A conservative estimate of the tx•tential subsurthce methane in these gas-charged sediments is of the order of 2.6 Tg, and its contribution to the atmosphere with an annual flux of 0.039 Tg CH4 appears to be quite significant. From our limited results coupled with worldwide reports, it is concluded that the seepage of methane (8 to 65 Tg) through the seabed of the continental shelves worldwide cannot be ignored for the estimati•m of global oceanic flux of methane and its budget. Background: Methane OccurrencesMethane, a highly reduced form of carbon is the most abundant organic chemical in the Earth's atmosphere [ Cicerone and Oreroland, 1988]. It is a radiatively active powerful greenhouse gas and plays an important role in atmospheric chemistry by intluencing both the ozone concentrations and infrared radiative flux. For about 10,000 years, the methane concentration remarked about 700 ppbv. For the last 200 years it has begun rising to the present concentration crabout 1700 ppbv. Methane concentration h• the global atmosphere during the last glaciation was only half that of the preindustrial Holocene [Stauffer eta!., 1988; Chappe!laz et al., 1990l. Blunier et al. [1995] have presented a continuous, high-re•lution record of atmospheric methane t¾om 8,000 to 1,000 yr B.P. from the GRIP (Greenland Ice Core Project) ice core in central Greenland. Unlike most other climate proxies, methane concernrations show significant variations up to 15% during the Holocene. They have proposed that variations in the hydrological cycle at low latitudes are the dominant control on the past levels of atmospheric methane, and the concentration increases during the Late Holocene, probably owing to an increasing contribution from the northern wetlands I Blunier el al., 1995]. Global increases in the concentration of greenhouse gases over the last 200 years are about 20% for CO2, 8% for N20, and over 200% for CH4 [Lorius, 1988]. Methane accounts for about 15% of the radiative forcing to the atmosphere, compared to 55% for CO2, 6% for N20, and 24% for the synthetic chlorofluorocarbons [Houghton e• al., 1990 I. The strong ability of methane to absorb infrared radiation, reradiated by the Earth's •rface, and its relatively short atmospheric lifetime of 8-12 years [Nisbet, 1989; Baljes and Bridges, 1994], coupled with the fact that a considerable amount of the atmospheric methane originates ti'om oceanic regions and subsurface seeps, makes the possibility of methane control an important option for addressing global climate change. However, it has been increasing in the atmosphere by about 1%/yr although the rate of increase has been declining in recent years [Steele et al., 1992]. Since the early report of gases in marine sediments [Emeo, and Hoggan, 1958], several investigators have published concen...

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A successful 3‐D seismic survey in the “no‐data zone,” offshore Mississippi delta: Survey design and refraction static correction processing

Carvill¹,

Faris²,

Chambers³

1996

SEG Technical Program Expanded Abstracts 1996

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Seismic No-Data Zone, Offshore Mississippi Delta: Part Ii-Using Geologic Information To Predict Acoustic Properties

Cited by 4 publications

References 0 publications

Advanced three‐dimensional seismic imaging of deep supercritical geothermal rocks in Southern Tuscany

Advanced three‐dimensional seismic imaging of deep supercritical geothermal rocks in Southern Tuscany

Potential distribution of subsurface methane in the sediments of the eastern Arabian Sea and its possible implications

A successful 3‐D seismic survey in the “no‐data zone,” offshore Mississippi delta: Survey design and refraction static correction processing

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