Geology and Reservoir Characteristics of a Cool-Water Carbonate Build-Up, Faxe Quarry, Denmark

Jens Martin Hvid¹, Frans Van Buchem², Emma Sheldon³, Frank Andreasen⁴, and Ida L. Fabricius^4
1DONG E&P Norge AS, Stavanger, Norway
²Maersk Oil Qatar, Doha, Qatar
³Geological Survey of Denmark and Greenland, Copenhagen, Denmark
⁴Technical University of Denmark, Lyngby, Denmark

In southern Scandinavia the Faxe limestone quarry exposes Danian (Lower Paleocene) cool-water carbonate deposits forming an isolated build-up that covers a few square kilometres. The build-up stands out relative to the regional carbonate system of the Danian across Denmark, which is broadly characterised by bryozoan limestone mounds with a general westward transition to more pure coccolithic mudstone in the North Sea basin. In the quarry the relative rare Scleractinian corals are uniquely exposed as mounds with heights up to 30 meters, and the rapid accumulation of Scleractinian corals appears to be the main reason for the Danian thickness anomaly at Faxe. A hypothetic localization due to seeping hydrocarbons causing proliferation of the Scleractinians is not very likely because the proven Paleozoic source rock potential was already realized in early Mesozoic times.

However, the location of Faxe above a local basement high points to a structural control of coral growth. A mapped lithostratigraphic horizon through the build-up reveals the large scale organisation of nested bryozoan mounds into three elongated ridges striking northwest-southeast. Above this horizon the main Scleractinian coral mounds grew towards a southern direction. Data for reservoir characterization of the build-up were collected as photos of the outcrop, petrophysical and petrographical data from cored wells and Ground Penetrating Radar sections. Old wells and old measured sections were used to make a reconstruction of the build-up and new nannofossil data made a cyclostratigraphic interpretation possible. Data from the southern part of the quarry were used to build a 3D geological model. The bryozoan limestone would be an acceptable hydrocarbon reservoir rock because it has higher permeability and lower entry pressure than North Sea chalk.

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