Western Baltic, Kattegat and Aarhus Bay (seismics preformed by GEUS)

The interpretation of the acoustical data concentrates on:

Interpretation of the general geological setting related to the formation and migrating of methane in the sediments

Classification of characteristic acoustical indications of methane in the sediments

Mapping of areas with gas-charged sediments

Attempts will be made to calibrate the acoustic signal to geochemical measurements on methane contents in sediments to be able to quantify the amount of methane gas as well as sub-bottom depth of the gas-zone in specific environments using acoustic data alone.

Skagerrak (sesmics performed by Univ. Hamburg)

The interpretation of the multi-channel seismic data focuses on:

Gas charged Quaternary sediments

Subcrops of gas charged Mesozoic strata

Correlation of pockmarks with subcropping and gas charged Mesozoic strata

Correlation of sediment tectonic with gassy Quaternary and Mesozoic strata

Link of each sampling site to the structural context

Origin of gas (biogene or thermogene) at active or passive fluid escape structures

Acoustic survey of bubble distribution (performed by GEUS)

The acoustic properties of sea bed sediments containing gas are dominated by the volume of gas contained in bubbles, the size of bubbles and the elastic properties of the sediment matrix.
In order to be able to quantify the gas volume in sediments, acoustical studies were made using the X-star sonar hydrophone combined with a newly developed software that allowed the hydrophone to send out narrow frequency bands, record and analyze the reflected acoustic signal.

By analyzing data form different settings it is the aim of the project to determine the gas bubble size distribution. Furthermore, the acoustic signal may be directly related to the gas content found by geochemical methane measurements in seepage areas, as the in-situ methane production in coarse sandy sediments may be considered negligible.

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