ALBERT

Description: Driven bysignificant economic benefits, the hydrocarbon industry developed sophisticated methods for the integration of geophysical and geochemical measurements with direct core observations. However, these techniques were developed primarily for sedimentary settings and have been applied only seldom in metamorphic settings. One outstanding example for comprehensive geophysical and borehole data integration is the COSC-1 borehole in the central Scandinavian Caledonides. It was drilled in 2014 and resulted in an extensive dataset to shed light on deformation during continental collision. Our study combines data from downhole logging and zero-offset vertical seismic profiling at COSC-1, with 2D and 3D seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. We show that there are powerful tools to distinguish between mafic and felsic lithologies in log-core correlation but that metamorphic settings bear special challenges for core-log-seismic integration. In contrast to sedimentary basins, reflections in the Seve Nappe Complex are not as distinct but we can link several of them to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. It appears that in spite of the metamorphic overprint around 417+/-9 Ma, the original configuration of the volcanic passive margin is partly preserved in the Seve Nappe Complex and it thus outlasted continent-continent collision including the nappe emplacement. Integration of borehole and three-dimensional geophysical data reveals lithological changes that can then be extrapolated in three dimensions to arrive at a better understanding of the compositionand geometry at mid-crustal levels. Furthermore, our results suggest that mid-crustal reflectivity at COSC-1 is primarily a function of pre-orogenic lithological variations which has to be considered when deciphering mountain building processes.

Description: Strong anisotropy of seismic velocity in the Earth crust poses serious challenges for seismic imaging. Where in situ seismic properties are not available the anisotropy can be determined from independent surface and borehole seismic profiles. This is well established for dense, long-offset reflection seismic data. However, it is unknown how applicable this approach is for sparse seismic reflection data with low fold and short offsets. Here, we show that anisotropy parameters can be determined from a sparse 3D data set at the COSC-1 borehole site in the Swedish Caledonides and that the results agree well with the seismic anisotropic parameters determined on core samples from laboratory measurements. Applying these anisotropy parameters during 3D seismic processing significantly improves the seismic imaging of the high amplitude reflections especially in the lower part of the borehole. Strong reflectors in the resulting seismic data align well with the borehole-derived lithology. Our results aid the interpretation and extrapolation of the seismic stratigraphy of the Lower Seve Nappe.

Description: The goal of core-log-seismic integration is to glean new scientific understanding from diverse datasets that span the millimeter to kilometer scale. Germany plays an important role in international scientific drilling, with major core curation and data management centres, as well as broad expertise in seismicdata acquisition, borehole logging and sediment core investigations. Springboarding from this solid foundation, we propose to establish a virtual Core-Log-Seismic Integration Research Centre to act as a nucleus for conceiving and running research projectsthat harvest the untapped potential of hundreds of scientific boreholes. We envisage that scientists from Germany, in collaboration with key international partners, should work closely together and provide the critical mass and long-term expertise to sustain the research centre. We see this an ideal way to foster collaboration within Germany and globally.In this presentation we will describe this new initiative and provide some examples of on-going and developing research projects that are underpinned by core-log-seismic integration methods. The examples will include investigations into submarine landslide processes (offshore New Zealand), gas hydrate formation (offshore Taiwan) and continental collision (onshore Sweden).