Elger, Judith , Berndt, Christian , Kästner, Felix, Pierdominici, Simona and Kueck, Jochem (2018) Results on Core-Log-Seismic-Integration in hard-rock environments using the ICDP drilling project COSC-1, Sweden . [Poster] In: AGU Fall Meeting 2018. , 10.-14.12.2018, Washington, D.C., USA .

Abstract

As part of the ICDP priority program “Collisional Orogeny of the Scandinavian Caledonides (COSC)” we are investigating the geophysical properties of the rocks from the Seve Nappe Complex (SNC) using the COSC-1 borehole (Sweden). This project has two main objectives. The first, geological aim is to establish a high-resolution seismic stratigraphy applying Core-Log-Seismic-Integration (CLSI) to a metamorphic setting to improve our understanding of the tectonic and structural geological processes that led to the formation of the SNC and, in particular, how shear stress was partitioned and how it affected the geophysical properties. The second, methodological objective aims at learning how the CLSI techniques can be applied for metamorphic rocks although they have been developed mainly for hydrocarbon reservoirs in lithified sediment rocks. Here, we use information from two sets of wireline logs and tie them to a 2D and 3D seismic surveys from the SNC, a multi-azimuthal walkaway vertical seismic profile, and a high-resolution zero-offset vertical seismic profile, and combine them through Log-Seismic-Integration (LSI). From density and sonic information we have generated synthetic seismograms and compared them to zero offset seismic traces and traces from the processed surface 3D seismic data that were extracted at the location of the borehole. As expected, the results show significant deviations between synthetic and measured seismograms due to seismic wave propagation artefacts, noise both in the seismic and in the downhole logging data, imperfect coupling of the tools in the boreholes and uncertainty in the depth measurements during logging as well as anisotropy in the seismic velocities. Nevertheless, we identify a number of prominent reflections that can be linked e.g. to amphibolite zones as well as to measured seismograms which will allow us to extrapolate the lithology from the borehole. In order to reveal physical properties of the methamorphic setting the next step is to improve the seismic processing with an iterative process to minimize the mismatch between the synthetic and measured seismograms.

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