Geological parameters in Winnipegosis pinnacle reef exploration, North Dakota and Saskatchewan

Conference · Fri Jul 01 04:00:00 EDT 1988 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6024381

Kissling, D L; Ehrets, J R

Winnipegosis pinnacle reefs range between 150 and 300 ft in height and up to 3 mi across, and their density distribution is several per township. They had accumulated as codiacean algae and peloid calcarenite mounds, capped by massive stromatolite boundstone, and fringed by stromatoporoid coral assemblages and detrital flanks during accelerating basin subsidence that had accompanied Winnipegosis platform-basin decoupling. Pinnacle reefs were terminated by increasing hypersalinity and toxicity during late Winnipegosis evaporative drawdown of the shelf sea. Postdepositional processes most responsible for preservation, enhancement, or loss of porosity and permeability in specific reef facies include prolonged vadose-zone leaching, early cementation or compaction, shallow-burial dolomitization, seepage reflux dolomitization and cementation, overdolomitization, and deep-burial brine invasion. Pinnacle reef exploration and exploitation must consider a hierarchy of riddles. These are (1) to locate relatively small structures within the vast basin regime, (2) to distinguish porous, oil-charged reefs from nonporous, wet, or salt-plugged reefs, and (3) to locate favorable reservoir bodies within heterogeneous reef structures. The initial task of finding reefs integrates geological and geophysical data, but remains a shotgun approach without a reef distribution model that comprehends epeirogenic, paleotectonic, and paleohydrographic factors. Selecting the right reef might be attempted through understanding Winnipegosis-Prairie diagenesis, or by formulating techniques for recognizing remote signpost of overdolomitization, salt plugging, and oil emplacement.

• Research Organization: Jackalope Geological Ltd., Boulder, CO (USA)
• OSTI ID: 6024381
• Report Number(s): CONF-8808223-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 72:7
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CANADA
DEPOSITION
EXPLORATION
FEDERAL REGION VIII
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
MINERAL RESOURCES
NORTH AMERICA
NORTH DAKOTA
PERMEABILITY
PETROLEUM DEPOSITS
POROSITY
REEFS
RESERVOIR ROCK
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SASKATCHEWAN
USA
WILLISTON BASIN