Imaging the sea surface using a dual-sensor towed streamer

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. V111-V118 ◽  
Author(s):  
Okwudili Orji ◽  
Walter Söllner ◽  
Leiv Jacob Gelius
Keyword(s):  
Seismic Data ◽  
Time Window ◽  
Finite Difference Methods ◽  
Surface Profile ◽  
Sea Surface ◽  
Data Sets ◽  
The North ◽  
Dual Sensor ◽  
The North Sea ◽  
Time Invariant

Sea-surface profile and reflection coefficient estimates are vital input parameters to various seismic data processing applications. The common assumption of a flat sea surface when processing seismic data can lead to misinterpretations and mislocations of events. A new method of imaging the sea surface from decomposed wavefields has been developed. Wavefield separation is applied to the data acquired by a towed dual-sensor streamer containing collocated pressure and vertical particle velocity sensors to obtain upgoing and downgoing wavefields of the related sensors. Time-gated upgoing and downgoing wavefields corresponding to a given sensor are then extrapolated to the sea surface where an imaging condition is applied so that the time-invariant shape of the sea surface can be recovered. By sliding the data time-window, the temporal changes of the sea surface can be correspondingly estimated. Ray tracing and finite-difference methods were used to generate different controlled data sets used in this feasibility study to demonstrate the imaging principle and to test the image accuracy. The method was also tested on a first field data example of a marginal weather line from the North Sea.

Velocity anisotropy of shales and depth estimation in the North Sea basin

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1411-1419 ◽  
Author(s):  
N. C. Banik
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Depth Estimation ◽  
Data Sets ◽  
Well Log ◽  
Simple Method ◽  
Velocity Anisotropy ◽  
Interval Velocity ◽  
The North ◽  
The North Sea

It is known that in the North Sea basin the depths to major reflectors as determined from surface seismic data are often larger than the well‐log depths. From a study of data sets which tie 21 wells, I found a strong correlation between the occurrence of the depth error and the presence of shales in the subsurface. Assuming that the error is caused by elliptical velocity anisotropy in shales, I measured the anisotropy from a comparison of the well‐log sonic data and the interval velocity profile obtained from the surface seismic data and also from a comparison of the seismic depth and the well‐log depth. It was found that the two methods of measurements agree with each other and also agree qualitatively with the previous laboratory measurements of anisotropy in shale samples. The results strongly suggest that the depth anomaly in the North Sea basin is caused by the velocity anisotropy of shales. A simple method to correct the seismic depth is given.

Effects of time-varying sea surface in marine seismic data

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. P33-P43 ◽  
Author(s):  
Okwudili C. Orji ◽  
Walter Söllner ◽  
Leiv-J. Gelius
Keyword(s):  
Imaging Technique ◽  
Sea Surface ◽  
Time Varying ◽  
Surface Imaging ◽  
The North ◽  
Dual Sensor ◽  
The North Sea ◽  
Marine Seismic ◽  
Seismic Measurements ◽  
Rough Sea

A method of imaging sea surfaces based on marine seismic measurements has recently been developed. The imaging technique is based on extrapolating decomposed wavefields obtained from dual-sensor streamers to the sea surface where an adequate imaging condition is applied. Earlier feasibility tests of the method involved only controlled data associated with frozen sea surfaces. Here, the issue of time-varying effects will be in focus. We introduced a modeling approach based on the Kirchhoff-Helmholtz integral and computed the scattered wavefield from time-varying rough sea surfaces (e.g., Pierson-Moskowitz sea surfaces). We generated data for a realistic wind speed and verify the robustness of the proposed sea surface imaging technique by taking into account possible effects of moving receivers as well as streamers with variable shape. We investigate the feasibility of estimating the surface wave velocity from the spectra of the imaged sea surfaces and finally present a successful application of the sea surface imaging technique to data from the North Sea.

scholarly journals Influence of Sea State on Sea Surface Height Oscillation from Doppler Altimeter Measurements in the North Sea

2018 ◽  
Vol 10 (7) ◽  
pp. 1100 ◽  
Author(s):  
Ferdinando Reale ◽  
Fabio Dentale ◽  
Eugenio Carratelli ◽  
Luciana Fenoglio-Marc
Keyword(s):  
North Sea ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Sea State ◽  
The North ◽  
The North Sea

Quaternary evolution of the northern North Sea

2020 ◽  
Author(s):  
Christine Batchelor ◽  
Dag Ottesen ◽  
Benjamin Bellwald ◽  
Sverre Planke ◽  
Helge Løseth ◽  
...  
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
3D Seismic ◽  
Quaternary Sediments ◽  
The North ◽  
The North Sea ◽  
Data Coverage ◽  
Northern North Sea ◽  
2D And 3D ◽  
3D Seismic Data

<p>The North Sea has arguably the most extensive geophysical data coverage of any glacier-influenced sedimentary regime on Earth, enabling detailed investigation of the thick (up to 1 km) sequence of Quaternary sediments that is preserved within the North Sea Basin. At the start of the Quaternary, the bathymetry of the northern North Sea was dominated by a deep depression that provided accommodation for sediment input from the Norwegian mainland and the East Shetland Platform. Here we use an extensive database of 2D and 3D seismic data to investigate the geological development of the northern North Sea through the Quaternary.</p><p>Three main sedimentary processes were dominant within the northern North Sea during the early Quaternary: 1) the delivery and associated basinward transfer of glacier-derived sediments from an ice mass centred over mainland Norway; 2) the delivery of fluvio-deltaic sediments from the East Shetland Platform; and 3) contourite deposition and the reworking of sediments by contour currents. The infilling of the North Sea Basin during the early Quaternary increased the width and reduced the water depth of the continental shelf, facilitating the initiation of the Norwegian Channel Ice Stream.</p>

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