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- Erlström, Mikael, et al.
(author)
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Stratigraphy and geothermal assessment of Mesozoic sandstone reservoirs in the Öresund Basin - exemplified by well data and seismic profiles
- 2018
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In: Bulletin of the Geological Society of Denmark. - 0011-6297. ; 66, s. 123-149
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Journal article (peer-reviewed)abstract
- The Øresund Basin in the transnational area between Sweden and Denmark forms a marginal part of the Danish Basin. The structural outline and stratigraphy of the Mesozoic succession is described, and a novel interpretation and description of the subsurface geology and geothermal potential in the North Sjælland Half-graben is presented. The subsurface bedrock in the basin includes several Mesozoic intervals with potential geothermal sandstone reservoirs. Parts of the succession fulfill specific geological requirements about distribution, composition and quality of the sandstones. A characterisation of these is presently of great interest in the attempt to identify geothermal reservoirs suitable for district heating purposes. The results presented in this paper include for the first time a comprehensive description of the stratigraphic intervals as well as the characteristics of the potential Mesozoic geothermal reservoirs in the Øresund region, including their distribution, composition and physical properties. This is illustrated by seismic cross-sections and well sections. In addition, results from analyses and evaluations of porosity, permeability, formation fluids and temperature are presented. Six potential geothermal reservoirs in the Mesozoic succession are described and assessed. Primary focus is placed on the characteristics of the reservoirs in the Lower Triassic and Rhaetian–Lower Jurassic succession. The study shows that the Mesozoic reservoir sandstones vary considerably with respect to porosity and permeability. Values range between 5–25% for the pre-Rhaetian Triassic sandstones, but are commonly > 25% for the Rhaetian–Lower Jurassic and Lower Cretaceous sandstones. The corresponding permeability rarely reaches above 500 mD for the pre-Rhaetian Triassic reservoirs, but often reach >1 Darcy for the Rhaetian–Lower Jurassic and the Lower Cretaceous sandstones. The interpreted formation temperatures for the reservoirs in the Øresund Basin are: 45–50°C at 1500 m, 60–70°C at 2000 m and 70–90°C at 2500 m depth . The combined results provide a geological framework for making site specific predictions regarding appraisal of viable geothermal projects for district heating purposes in the region as well as reducing the risk of unsuccessful wells
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