Dolomitization and porosity development in the middle and upper Wabamun Group, southeast Peace River Arch, Alberta, Canada
- Unocol Science and Technology, Brea, CA (United States)
- Consultant, Calgary (Canada)
Dolomitization and fracturing are critical to porosity development in most Wabamun Group reservoirs in the southern part of the Peace River arch. Cores from Peoria, Normandville, and Eaglesham fields and adjacent areas were examined to determine the relationship between depositional facies, dolomitization, fracturing, and porosity. Three-dimensional (3-D) seismic data indicate that most upper Wabamun dolomites are coincident with mound-like structural highs at the top of the Wabamun, with structural relief due largely to differential compaction between dolomite and adjacent limestone. When this depositional/diagenetic model for dolomitization was integrated into 3-D seismic interpretations, Canadian Occidental`s discovery rate in the Wabamun increased from approximately 25 to 80%. The early dolomite is facies, fabric, and mineralogy selective with some burrow fills and aragonitic mollusks being preferentially dolomitized in dolomitic limestones. Most fracturing occurred after early, replacive Dolornitization. Late dolomitization, karst-like dissolution and collapse apparently were localized near the margins of the early dolomites where adjacent limestones were dolomitized or dissolved. Dissolution of calcite in partially dolomitized limestones resulted in geopetal accumulations of dolomite rhombs (porous sucrosic dolomite) in some fractures and burrow fills. Hydrothermal fluids apparently moved updip through the underlying Winterburn and/or Leduc formations, and then upward through porous, early dolomites in the Wabamun, causing Dolomitization of adjacent limestones and karst-like dissolution. Stable oxygen isotope ratios of the dolomites are quite variable ({delta}{sup 18}O ranges from -2.0 to -11.4{per_thousand}, PDB), supporting multiple stages of dolomitization during progressive burial.
- OSTI ID:
- 96201
- Report Number(s):
- CONF-941065--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 9 Vol. 78; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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