Preservation of high primary porosity in Paleozoic crinoidal and bioclastic grainstones: Mississippian and Permian subsurface examples from western Canada and Texas

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5583328

Eby, D E ^[1]; Kirkby, K C ^[2]

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1. Marathon Oil Co., Littleton, CO (United States)
2. Univ. of Wisconsin, Madison (United States)

Limestone reservoirs with anomalously high porosity and permeability exist in several Paleozoic basinal settings in western North America. They are commonly either crinoidal or bioclastic grainstones that escaped the varied diagenetic environments that most carbonate shelves and slopes experience during sea-level fluctuations. Thus, these diagenetically 'conservative' settings can preserve most of the primary depositional porosity in calcarenites because of sedimentation and burial within normal marine basinal waters. These excellent reservoirs are often encased in deep marine, highly organic shales which may serve as both source rock and seal. Several subsurface examples of remarkable primary porosity occur within Mississippian Waulsortian buildups of western Canada and north-center Texas. Buildups within the Pekisko Formation of Alberta, for instance, contain abundant flanking crinoidal/bryozoan grainstones with up to 25% primary porosity and 10 d permeability. Muddy core facies with productive flank and capping calcarenites are up to 300 ft (90 m) thick and 600-1,200 ft (182-364 m) in diameter. The Bowar 'reef complex' in the Chappel Formation of Stephens County, Texas (2.6 MMBO to date) is similar in many respects to the Canadian buildups. Diagenetic 'conservatism' has also promoted excellent reservoir quality within the outer slope to basinal lower Permian bioclastic grain-flow deposit ('Wolfcamp detrital') plays of the eastern Midland basin where significant diagenesis was arrested after basinal deposition. Interpretations of these examples based upon core and outcrop control provide analogs for future exploration and exploitation in highly porous basinal carbonate reservoirs.

• OSTI ID: 5583328
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
ALBERTA
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
RESERVOIR ROCK
POROSITY
TEXAS
CARBONIFEROUS PERIOD
ECHINODERMS
GEOLOGIC HISTORY
GEOLOGIC TRAPS
LIMESTONE
LITHOLOGY
PERMEABILITY
PERMIAN PERIOD
SOURCE ROCKS
ANIMALS
AQUATIC ORGANISMS
BENTHOS
CANADA
CARBONATE ROCKS
DEVELOPED COUNTRIES
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC DEPOSITS
INVERTEBRATES
MINERAL RESOURCES
NORTH AMERICA
PALEOZOIC ERA
RESOURCES
ROCKS
SEDIMENTARY ROCKS
USA
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration