POROSITY AND PERMEABILITY VARIATIONS IN A TIGHT GAS SANDSTONE RESERVOIR ANALOGUE, WESTPHALIAN D, LOWER SAXONY BASIN, NW GERMANY: INFLUENCE OF DEPOSITIONAL SETTING AND DIAGENESIS

Autor: Ivy Becker, Marita Felder, Christoph Hilgers, P. Wüstefeld, Bastian Koehrer
Rok vydání: 2017
Předmět:
Zdroj: Journal of Petroleum Geology. 40:363-389
ISSN: 0141-6421
DOI: 10.1111/jpg.12685
Popis: Understanding the spatial variability of reservoir properties in tight gas sandstones can significantly reduce uncertainties in reservoir characterization. This study focuses on two outcrops of Upper Carboniferous (Westphalian D) fluvial sandstones in the southern part of the Lower Saxony Basin, NW Germany, which are analogues for tight, gas-producing reservoir rocks at fields in the north of the basin. Large-scale differences in reservoir quality occur between the two outcrops which are separated by a distance of approximately 15 km and by 600 m of stratigraphy. Smaller-scale heterogeneities in the form of channel geometries occur within individual fluvial cycles, as evidenced in a 30 m (high) by 150 m (long) porosity-permeability profile at one of the outcrops studied. In the Woitzel quarry, lower Westphalian D deposits consist of fining-upwards cycles of channel and bar sandstones with intercalated floodplain sediments and coal seams. In abandoned quarries at the Huggel location, upper Westphalian D strata are composed of grey and red coloured sandstones which suggest deposition in a fluvial – alluvial plain environment under increasingly arid conditions. Reservoir quality is higher in the upper Westphalian D sandstones at Huggel (permeability: up to 1 mD; mean porosity: 19%) than in the lower Westphalian D sandstones at Woitzel (permeability
Databáze: OpenAIRE
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