Predicting permeability of low enthalpy geothermal reservoirs: A case study from the Upper Triassic − Lower Jurassic Gassum Formation, Norwegian–Danish Basin.

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  • Rikke Weibel, GEUS - Danmarks og Grønlands Geologiske Undersøgelse, Denmark
  • Mette Olivarius, GEUS - Danmarks og Grønlands Geologiske Undersøgelse
  • ,
  • Lars Kristensen, GEUS - Danmarks og Grønlands Geologiske Undersøgelse, Denmark
  • Henrik Friis
  • Morten Leth Hjuler, GEUS - Danmarks og Grønlands Geologiske Undersøgelse, Denmark
  • Claus Kjøller, GEUS - Danmarks og Grønlands Geologiske Undersøgelse, Denmark
  • Anders Mathiesen, GEUS - Danmarks og Grønlands Geologiske Undersøgelse, Denmark
  • Lars Henrik Nielsen, GEUS, Geological Survey of Denmark and Greenland
This paper aims at improving the predictability of permeability in low enthalpy geothermal reser-voirs by investigating the effect of diagenesis on sandstone permeability. Applying the best fittedporosity–permeability trend lines, obtained from conventional core analysis, to log-interpreted poros-ity, is crucial in estimating reservoir permeability from logs. Petrographical analysis of sandstones fromthe Gassum Formation reveals lithological and diagenetic controls on plug permeability and porosity.Porosity–permeability trend lines vary with grain size for the shallowly buried sandstones (<2500 m).Deeply buried sandstones (>2500 m) from a steeply sloping porosity–permeability trend line since thepore-throat diminution due to quartz, ankerite and illite precipitation affects the permeability more thanporosity, as evident from mercury injection curves. Permeabilities lower than the general trend for eachgrain-size group are caused by early diagenetic siderite cement, late diagenetic illitic clays and/or detritalclays. Permeabilities of sandstones deposited under humid well-vegetated conditions in marine and par-alic environments, such as the Gassum Formation, are primarily dependent on burial history (maximumburial depth) and depositional environment.
Original languageEnglish
JournalGeothermics
Volume65
Pages (from-to)135-157
ISSN0375-6505
DOIs
Publication statusPublished - Jan 2017

    Research areas

  • Porosity–permeability trends, Grain size, Depositional environment, Burial depth, Diagenesis, Pore-throat size distribution

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