About This Item
- Full text of this item is not available.
- Abstract PDFAbstract PDF(no subscription required)
Share This Item
The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Confined-flow Turbidite Reservoirs: Plio-Pleistocene,
Ship Shoal - Ewing Banks - Green Canyon areas, Offshore Louisiana
By
Mobil Oil Corporation, Dallas, Texas, USA
Seismic facies and high-resolution biostratigraphic
analysis provide a sequence
stratigraphic framework for interpreting
lateral distribution of sand-prone facies
and possible reservoir connectivity in the
Ship Shoal 351-358 to Ewing Bank 988
minibasin, offshore Louisiana. The interval
of interest is an isochron thick interpreted
as a lowstand systems tract
deposited in bathyal water depths within
an intraslope-minibasin. This basin
is approximately 50 km from the
age
-equivalent shelf/slope break. The
isochron thick was deposited between the
late Pliocene Discoaster pentaradiatus
and early Pleistocene Discoaster brouweri
Condensed Sections, as calibrated by data
from five wells penetrating this interval
within the intraslope basin.
The D. pentaradiatus - D. brouweri sequence consists of the synclinal fill of a salt withdrawal basin forming an isochron thick that thins onto adjacent salt-cored structural highs. This isochron interval was subdivided into four seismic facies and each was calibrated with local well data. Mapped patterns of these seismic facies suggest a network of channel-form systems supplying sediment to depositional lobe-forms within a slope valley. Sandy sediments were transported by gravity-driven processes from the shelf, down slope through a valley and into this local intraslope-minibasin. Upon filling this minibasin, the gravity-driven sediments spilled farther south into the area of the Green Canyon 18 field, where these sandstones are the main reservoir. The mapping of channel-and levee-form patterns suggests that the transport process included turbid flow with consequent overbanking of the channel and levee formation.
Following the above analysis, three wells and two sidetracks were drilled to further test the prospectivity of the area. Rock type and hydrocarbon predictions based on calibrated seismic facies analysis were confirmed by the new wells.
Sandstones occur within the axes of isochron thicks and shales
dominate the isochron
thins over paleo-highs
with gradational facies
between. Hydrocarbon accumulation occurs in two
settings: 1) channel-fed lobes with blocky log character yield hydrocarbons within areas of structural closure; and 2) overbank facies that contain hydrocarbons in low-resistivity pay both within and outside of structural closure
Local abundance peaks of planktonic microfossils provide correlation
control between the four depositional lobes of this lowstand deposit. The
biostratigraphic
data and paleogeographic interpretation suggest that each depositional lobe is separated from the others by mudstone
drapes, resulting in discrete partitioning of reservoir sands.
Unnumbered Figure. Gulf of Mexico Gravity Flow Event; from Shanmugam (1993, AAPG Bulletin) artwork Mark Lindsey, Mobil Technology Company.
End_of_Record - Last_Page 11---------------