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Low-frequency analysis from permeable and fractured rocks in the central North Sea - A possible Krauklis-wave phenomenon
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 3
Abstract
Using the Gabor-Morlet transform, low-frequency amplitude anomalies from highly permeable and fractured rocks were investigated. For this purpose, a 3D broadband seismic dataset from Johan Sverdrup field in the central North Sea was used. Low Q values of about 25 and 30 are observed from the highly permeable Late Jurassic Intra-Draupne Fm and the fractured carbonates of the Svarte Fm, respectively. The low-frequency amplitude anomalies from the Late Jurassic Intra-Draupne Fm are observed in areas where the reservoir is relatively thick, whereas higher frequencies are observed where the reservoir is less thick. A three-layer elastic modelling was also performed which suggests a decrease in the dominant frequency as the thickness of the middle, gas-saturated layer increases due to the tuning effect. Moreover, the low-frequency anomalies observed from the fractured Svarte Fm were found to have an obvious correlation with the faults (fractures) indicated by the high-resolution most-negative-curvature attribute.