Predicting porosity distribution within oolitic tidal bars
- Dominion Appalachian Development Inc., Jane Lew, WV (United States)
- Univ. Dept. of Geology and Geography, Morgantown, WV (United States)
The Mississippian Greenbrier Limestone is a major gas reservoir in the Appalachian basin, but its complex porosity patterns often deter active exploration. In southern West Virginia, the reservoir consists of oolitic tidal bars which are composites of smaller shoals. Porosity trends closely follow the ooid-grainstone facies which occupied shoal crests, where coarse-grained, well-sorted ooid sand was generated with either unidirectional or bidirectional cross-beds. Nonporous packstone occurred in adjacent tidal channels, and a transitional grainstone/packstone facies of marginal porosity was situated along the flanks of the shoals. The key to drilling successful wells is in understanding the complex internal geometry of Greenbrier ooid shoals. A well penetrating the oolite with good porosity and bimodal cross-beds should be offset perpendicular to the dip directions, that is, parallel to the shoal axis. However, a well penetrating thin, porous limestone with one dominant cross-bed azimuth should be offset opposite to that dip direction, that is, up the flank of the ooid shoal. Shaly interbeds characterize the edges of the shoals and mark the limit of productive wells. Schlumberger`s Formation MicroScanner (FMS) log, which provides data on both lithology and cross-bedding, has proven to be a useful tool in predicting the distribution of oolite porosity.
- OSTI ID:
- 411924
- Report Number(s):
- CONF-9610180-; ISSN 0149-1423; TRN: 96:005901-0056
- Journal Information:
- AAPG Bulletin, Vol. 80, Issue 9; Conference: American Association of Petroleum Geologists (AAPG) gulf coast association of geological societies meeting, San Antonio, TX (United States), 2-4 Oct 1996; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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