Diagenetic history, porosity development, and permeability pathways in Mississippian Greenbrier oolites of West Virginia

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5677275

Smosna, R ^[1]; Kelleher, G T ^[2]

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1. West Virginia Univ., Morgantown (United States)
2. CNG Producing Co., New Orleans, LA (United States)

In the Rhodell gas field of southern West Virginia, grainstones of the union and Pickaway oolite members have initial potentials that exceed 2.0 MMCF GPD and reserves of up to 1 bcf per well, Thirty-two wells in the field are productive from the Greenbrier. Porosity is fair with a mean value of 9.5%, and permeability is variable but generally poor, averaging only 0.15 md. The production rate for these wells is directly related to the oolites' diagenetic history. Pores are intragranular and 1-5 {mu}m in size. Ooids underwent recrystallization during meteoric diagenesis, and they now consist of aphanocrystalline calcite. Micropores with relatively large throats and numerous interconnections exist between the very fine calcite rhombs. The pores are arranged in alternating laminae of the ooids' cortex, hinting that the ooids were originally bimineralic. Intergranular pore space has been largely occluded by successive generations of cement, including isopachous calcite rims that precipitated in the marine environment. Following mineral stabilization, some grainstones were subjected to chemical compaction, which produced a fitted fabric. The compacted limestones possess large contact areas between neighboring ooids and, consequently, and enhanced permeability and exceptional production. In contrast, limestones with an early marine cement had the strength to resist compaction, and the porous ooids have small point-to-point contacts. Because the pathways for gas migration are narrow, tortuous, and discontinuous, permeability in these rocks is low. The best reservoirs, therefore, are ooid grainstones that escaped early marine cementation but underwent meteoric diagenesis and chemical compaction.

• OSTI ID: 5677275
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:8; ISSN AABUD; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
CARBONATE ROCKS
CARBONIFEROUS PERIOD
COMPACTING
CRYSTAL STRUCTURE
DEVELOPED COUNTRIES
DIAGENESIS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
LIMESTONE
MICROSTRUCTURE
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
PALEOZOIC ERA
PERMEABILITY
POROSITY
RECRYSTALLIZATION
RESERVOIR ROCK
RESOURCES
ROCKS
SEDIMENTARY ROCKS
USA
WEST VIRGINIA