Seismic Characterisation of Gas-rich Near Surface Sediments in the Arkona Basin, Baltic Sea |
| |
| Authors: | M Mathys O Thießen F Theilen M Schmidt |
| |
| Institution: | (1) Institute of Geosciences, Christian Albrechts University, D-24098 Kiel, Germany;(2) Renard Centre of Marine Geology (RCMG), University of Ghent, Krijgslaan 281, S8, B-9000 Gent, Belgium |
| |
| Abstract: | Gas in sediments has become an important subject of research for various reasons. It affects large areas of the sea floor
where it is mainly produced. Gas and gas migration have a strong impact on the environmental situation as well as on sea floor
stability. Furthermore, large research programs on gas hydrates have been initiated during the last 10 years in order to investigate
their potential for future energy production and their climatic impact. These activities require the improvement of geophysical
methods for reservoir investigations especially with respect to their physical properties and internal structures. Basic relationships
between the physical properties and seismic parameters can be investigated in shallow marine areas as they are more easily
accessible than hydrocarbon reservoirs. High-resolution seismic profiles from the Arkona Basin (SW Baltic Sea) show distinct
‘acoustic turbidity’ zones which indicate the presence of free gas in the near surface sediments. Total gas concentrations
were determined from cores taken in the study area with mean concentrations of 46.5 ml/l wet sediment in non-acoustic turbidity
zones and up to 106.1 ml/l in the basin centre with acoustic turbidity. The expression of gas bubbles on reflection seismic
profiles has been investigated in two distinct frequency ranges using a boomer (600–2600 Hz) and an echosounder (38 kHz).
A comparison of data from both seismic sources showed strong differences in displaying reflectors. Different compressional
wave velocities were observed in acoustic turbidity zones between boomer and echosounder profiles. Furthermore, acoustic turbidity
zones were differently characterised with respect to scattering and attenuation of seismic waves. This leads to the conclusion
that seismic parameters become strongly frequency dependent due to the dynamic properties of gas bubbles. |
| |
| Keywords: | Arkona Basin P-wave velocity shallow gas velocity dispersion |
| 本文献已被 SpringerLink 等数据库收录！ |
|
