Fletcher field: a Silurian patch/barrier-reef complex in southwestern Ontario
The importance of reef growth to Silurian oil and gas production in the Michigan basin is reflected in the large number of studies that have been conducted. Unfortunately, most of these studies have focused on pinnacle reefs, with patch and barrier reefs being virtually ignored, although they represent viable oil and gas exploration targets. Many patch reefs in Ontario also represent targets for enhanced oil recovery projects. Without detailed geologic studies, these projects cannot be readily implemented. A recent sedimentologic study defined the facies distribution of a patch- and barrier-reef complex and its associated producing zones (A-1 carbonate). The Fletcher field, located in southwestern Ontario, was chosen for study. Structures and facies relationships were defined using nine cored holes and geophysical well logs. In addition, detailed studies were made of the clay mineralogy and the controversial Guelph A-1 carbonate contact. Defined facies relationships indicate that the Fletcher patch/barrier reef differs in many respects to pinnacle reefs. The facies are simpler and fewer, consisting of a poorly zoned reef core overlain by a micritized reef-top, lagoonal, and supratidal sequence. The origin of the green shale at the Guelph A-1 contact is interpreted as resulting partly from subaerial exposure and partly from the concentration of insolubles by pressure solution. The clay mineralogy consists of a monomineralic assemblage of illite. The amount and distribution of this assemblage would not significantly affect enhanced oil recovery.
- Research Organization:
- Univ. of Waterloo, Ontario
- OSTI ID:
- 7053582
- Report Number(s):
- CONF-8610158-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:8; Conference: AAPG Eastern section meeting, Ann Arbor, MI, USA, 1 Oct 1986
- Country of Publication:
- United States
- Language:
- English
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03 NATURAL GAS
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EXPLORATION
RESERVOIR ROCK
ONTARIO
PETROLEUM DEPOSITS
CARBONATE ROCKS
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SILURIAN PERIOD
CANADA
GEOLOGIC AGES
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MINERAL RESOURCES
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