GNGTS 2015 - Atti del 34° Convegno Nazionale

32 GNGTS 2015 S essione 3.1 (TWT >3.5 s). These anomalies show a flat inner saucer geometry, often bounded by an inclined sheet that crosscuts upwards the seismofacies C, and deform the overburden reflectors in a gently symmetrical antiformal fold. The amplitude anomalies, which develop in the second level of emplacement (3.5 s < TWT < 2.7 s), show a concave-upwards saucer-shaped morphology and are characterized by the formation of two inclined sheets, often one steeper than the other. Moreover, some of these bodies show T- and F-shaped or antiformal morphology. At the third level (TWT <2.7 s), only two sills, developed within the seismofacies A, crosscut the seismo-stratigraphic reflectors, obliterate the underlying seismofacies B and deform the overlying reflectors as a structural dome. Furthermore, by applying the seismic attributes, it is possible to better distinguish the sills based on the strong Reflection Strength and Sweetness response, which allow to isolate the seismic anomalies from the low amplitude background. Likewise, the Instantaneous Phase consents to distinguish, particularly within the seismofacies B, the seismic bodies characterized by a composite shape and masked in a chaotic facies. The Instantaneous Frequency is useful to differentiate the igneous bodies on the basis of the frequency values, always lower than the host-rock. According to the seismic attributes, the results obtained by the application of the CWT permit to classify the anomalies as bodies with a frequency range of 25-30 Hz. Moreover, this tool permits to characterize the bodies based on their geometrical features and it is fundamental to compute thickness, lateral extent, emplacement depth, diameter-to-depth ratio and related- fold amplitude of the sills. Furthermore, from the obtained measurements it is possible to understand the relations between thickness and emplacement depth, to compare thickness and the related-fold amplitude and to compute the relationship between these parameters. This work can supply new inputs improving the knowledge of the stratigraphy, of the geological setting and of the evolution of the investigated area. The achieved characterization of the igneous bodies can be of crucial importance for the hydrocarbon exploration. The presence of igneous intrusions in a petroleum system could cause important effects on the maturation of the source rocks, on the creation of structural and stratigraphic traps and, finally, could affect the oil migration pathway (Holford et al. , 2012; Thomson, 2007; Thomson et al. , 2008; Svensen et al. , 2006). References Barnes, A. E.; 2001: Seismic attributes in your facies. CSEG Recorder, 41-47. Debauchies, I.; 1988: Orthonormal bases of Compactly supported wavelets . Communication on Pure and Applied Mathematics, 41 , 909-996. Hart, B.S.; 2008: Channel detection in 3-D seismic data using sweetness . AAPG Bulletin, 92 , 6, 733-742. Holford, S.P., Schofield, N., MacDonald, J.D., Duddy, I.R. and Green, P.F.; 2012 : Seismic analysis of igneous systems in sedimentary basins and their impacts on hydrocarbon prospectivity: examples from the southern Australian margin . APPEA Journal, 229-252. Mallat, S.G.; 1989: ATheory forMultiresolution Signal Decomposition: The avelet Representation. IEEE transactions on pattern analysis and machine intelligence, 2 , 7, 674-693. Riedel, M., Collett, T.S., Kumar, P., Sathe, A.V. and Cook, A.; 2010: Seismic imaging of a fractured gas hydrate system in the KrishnaeGodavari Basin offshore India . Marine and Petroleum Geology, 27 , 1476-1493. Rocchi, S., Mazzotti, A., Marroni, M., Pandolfi, L., Costantini, P., Bertozzi, G., Di Biase, D., Federici, F. and Lô, P.G.; 2007: Detection of Miocene saucer-shaped sills (offshore Senegal) via integrated interpretation of seismic, magnetic and gravity data . Terra Nova, 19 , 232-239. Sadowsky John; 1996: Investigation of Signal Characteristics Using the Continuous avelet Transform. Johns Hopkins APL Technical Digest, 17 , 3, 258-269. Satyavani, N., Kalachand S., Malcolm L. and Kumar,B. J. P.; 2008: Seismic attribute study for gas hydrates in the Andaman Offshore India . Mar Geophys Res, 29 , 167-175. Svensen, H., Jamtveit, B., Planke, S. and Chevallier, L.; 2006: Structure and evolution of hydrothermal vent complexes in the Karoo Basin, South Africa . Journal of the Geological Society, London, 163 , 671-682. Subrahmanyam, D. and Rao, P.H.; 2008: Seismic Attributes- A Review . 7 th International Conference & Exposition on Petroleum Geophysics; Hyderabad, India.