Low-frequency Analysis from Permeable and Fractured Rocks in the Central North Sea - A Possible Krauklis-wave Phenomenon
S.S. Ahmad, W. Weibull, R.J. Brown and A. Escalona
Event name: 79th EAGE Conference and Exhibition 2017
Session: Seismic Interpretation and Attributes
Publication date: 12 June 2017
Info: Extended abstract, PDF ( 1.03Mb )
Price: € 20
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.