VARIATIONS IN PETROPHYSICAL PROPERTIES OF UPPER PALAEOZOIC MIXED CARBONATE AND NON- CARBONATE DEPOSITS, SPITSBERGEN, SVALBARD ARCHIPELAGO

The Late Carboniferous -Early Permian Gipsdalen Group and the Early to Late Permian Templefjorden Group are known hydrocarbon plays in the Arctic region, e. g. on the Finnmark Platform, Loppa High and Sverdrup Basin. Time-equivalent deposits crop out on the island of Spitsbergen and consist of mixed carbonate and non-carbonate (primarily siliciclastic, siliceous, organic-carbon rich and clayey) sediments deposited in continental to deep-marine settings. In rock samples (n = 73) collected from five outcrop locations on Spitsbergen, thin-section analysis showed the presence of ten microfacies types ranging from claystones and spiculitic cherts to rudstones and dolostones. Petrophysical and textural properties of the samples were measured to evaluate the link with the acoustic (P-and S-wave) velocities of these generally tight rocks, which have an average porosity of about 2%. Variations in acoustic velocity measurements primarily depend on variations in mineralogical composition (silica versus carbonate) and, to a lesser extent, on variations in porosity and bulk density. Pore networks in the sediments are dominated by microporosity and (micro) cracks, followed by interparticle porosity. Recrystallization effects and pore shape variations show a lesser effect on the P-wave velocity. Clay content does not exceed 12.7% and also has a secondary impact on the acoustic velocities. Defining which textural and physical parameters control the acoustic properties of these carbonate and non-carbonate sedimentary rocks will help with the interpretation of the seismic response of equivalent deposits in the subsurface.