Suspension- and current-deposit reservoirs in the Delaware basin: Trends and cycles in siltstones of the Permian Bone Spring Limestone
- Sandia National Lab., Albuquerque, NM (USA)
- Harvey E Yates Petroleum Co., Roswell, NM (USA)
Cores show that siltstone to very fine-grained sandstone oil reservoirs within the Permian Bone Spring Limestone are composed of submillimeter- to centimeter-thick sedimentation laminae. Blanketing of small-scale topography suggests that the laminae were deposited over wide areas as sediment settled vertical to the sea floor. Superimposed on the event laminae, were (1) background sedimentation of dolomitic, organic-rich, mudstone, (2) invertebrate burrowing, and (3) reworking by gentle bottom currents. Currents produced wispy ripply bedding and starved ripple forms that were draped by later deposits. Paleoflow was subparallel to the basin margin. Several sedimentation patterns occur within the formation. Three clastic intervals 25-50-m thick are interbedded with dolomitic mudstones of similar thickness. The clastic intervals are composed of three to six siltstone beds, each up to 25-m thick. Upsection within the beds increases in event-laminae, thickness, bioturbation, and current reworking. Other reports have suggested that these are turbidite-fan deposits, but locally, paleocurrent orientations and the lack of diagnostic assemblages and sequences of sedimentary structures argue against this interpretation. Rather, some of these deposits compare favorably with the few existing sedimentologic descriptions of Quaternary dust storm deposition in marine basins. The siltstone beds may also record deflation of the exposed adjacent shelf during lowered sea level. Very fine grain size and extensive carbonate cementation produce 5-10 pd permeability and 4-15% porosity. Sedimentary laminations cause significantly reduced vertical permeability where they are not disrupted by bioturbation, but permeability may be enhanced by natural fractures. Some reservoir thickenings are attributed to the formation of giant ripples by bottom currents, dictating a different exploration rationale than the turbidite-fan model.
- OSTI ID:
- 6676886
- Report Number(s):
- CONF-900605-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
NEW MEXICO
PETROLEUM DEPOSITS
RESERVOIR ROCK
EXPLORATION
GEOLOGIC FRACTURES
LIMESTONE
PERMEABILITY
POROSITY
QUATERNARY PERIOD
SANDSTONES
SEDIMENTARY BASINS
SILTSTONES
CARBONATE ROCKS
CENOZOIC ERA
FEDERAL REGION VI
GEOLOGIC AGES
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020200* - Petroleum- Reserves
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580000 - Geosciences