Porosity and permeability in the Graminia Formation, Upper Devonian Winterburn Group in the Germain Field, northeastern Alberta

  • Author / Creator
    Black, Meghan E
  • The Upper Devonian Graminia Formation (Winterburn Group) found in the Germain Field of northeastern Alberta includes the Blueridge Member (Frasnian) and the Upper Graminia Member (Famennian). A green silty-shale paleosol overlies the formation in this area. The bitumen-bearing dolostones of this formation are divided into Facies A, B, C, D, E, and F based on mineralogy, fabric, and cement types. Facies A, B, C, and E are formed of very finely to finely crystalline dolomitic siltstones to silty dolostones that are variably cemented with calcite and dolomite. Facies D is a green silty-shale bed that lies between Facies C and E. Facies F is a powdered dolomite cemented with bitumen. The sediments of the Blueridge Member were deposited during a third order regression in an inner-ramp setting. The sediments of the Upper Graminia Member were deposited during a fall in sea level that caused the ramp to shallow into the peritidal to supratidal zone. The precise timing and formation of dolomite is not known, but is thought to be sabhka-related based on the depositional framework. Facies F (powdered dolomite) may have been produced by diagenetic changes associated with a period of karst/exposure. Porosity values range from 3 to 40% and average permeability values range from 5 to 450 md. The main types of porosity are intergranular/intercrystalline (very common), vuggy (common) and fracture (rare). The permeability is controlled by the intergranular/intercrystalline pores and fractures. The porosity and permeability values do not display any predictable patterns across the Germain Field.

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    Master of Science
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