Seismicly transparent areas 3D

Description

The maps “Amplitude anomalies” represent the distribution of gas indicators in the form of amplitude anomalies in seismic data, such as bright spots, gas chimneys, seismic transparent zones and velocity pull-downs. The study area covers the German North Sea sector and the depths of the first 1.000 m below the seabed. Various seismic data were available as data bases: approx. 30.000 km 2D data and approx. 4.000 km² 3D data. The mapping of amplitude anomalies indicating gas serves as a basis for further investigations into near-surface natural gas deposits in the German North Sea sector. The near-surface gas deposits up to 1.000 m depth in neighbouring countries suggest that there could also be near-surface natural gas reserves in the German North Sea sector. Three of the Dutch near-surface natural gas deposits, near the German-Dutch border, are already in production (Muntendam-Bos et al., 2009). This shows that such natural gas reserves are a potential source of energy. If smaller natural gas deposits were to be found near planned wind farms, natural gas could be extracted and burned directly on site, and during windtimes it could propel turbines. This combination could enable a continuous energy supply. Since natural gas in the sediment can negatively affect the building ground properties, knowledge about the distribution of natural gas deposits in the depths of the foundation depth of wind turbines is also important from this point of view. The location of the mapped seismic transparent zones is marked magenta. Seismicly transparent zones in seismic data can indicate gas in the underground. These amplitude anomalies are characterised by significantly attenuated seismic amplitudes. This phenomenon can arise both by scattering or absorbing the acoustic signals on finely distributed gas in the pore space as well as by the almost complete reflection at a boundary to a gas-carrying layer due to the high impedance contrast. The almost complete reflection can be observed mainly on very high-frequency hydroacoustic data. Seismicly transparent zones can occur laterally narrowly limited, e.g. below bright spots, but also in larger areas. Striking in the German North Sea sector is the area southeast of Helgoland, which covers an area of approximately 500 km²; the so-called Helgoland Schlickloch (Hebbeln et al., 2003; by Haugwitz et al., 1988). Seismicly transparent zones must also be interpreted as indications of gas and do not allow a reliable statement about gas deposits. Literature: Hebbeln, D., Scheurle, C., and Lamy, F., 2003. Depositional history of the Helgoland mud area, German Bight, North Sea. Geo-Marine Letters 23, 81-90. Muntendam-Bos, A. G., Wassing, B. B. T., Heege, J. H. t., Bergen, F.v., Schavemaker, Y.A., Gessel, S. F. v., Jong, M. L. d., Nelskamp, S., Thienen-Visser, K. v., Guasti, E., Belt, F. J. G. v. d., and Marges, V.C., 2009. Inventory non-conventional gas. TNO, Utrecht. by Haugwitz, W., Wong, H. K., and Salge, U., 1988. The Mud Area Southeast of Helgoland: A reflection Seismic Study. Mitt. Geol.-Paleont. Inst. Univ. Hamburg 65, 14.

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