Reservoir Heterogeneity and Characterization in Deltaic
Depositional
Systems—Outcrop Analogs for Nova Scotia's Offshore Developments
Grant D. Wach and Hasley L. Vincent
Dalhousie
University, Halifax, NS
Fluvial systems fed large deltas through the Mid-Jurassic and Early
Cretaceous, offshore Nova Scotia. These ancient deltaic
systems provide the
reservoirs within the Sable gas project. The
deltaic
systems were mixed,
modified by waves and tides; modifications that added complexity to the
reservoirs. Channels within
deltaic
environments
are difficult to correlate in
the subsurface with numerous permeability baffles and barriers that create
reservoir heterogeneities that can result in significant bypassed hydrocarbons.
Incorporating outcrops of analogous depositional systems can reduce risk
associated with reservoir modeling and scaling issues. However, outcrops with
3-D exposures of deltaic
systems with well-exposed architectural elements and
details of reservoir heterogeneity for reservoir modeling and field optimization
are limited. Nova Scotia has no outcrops with similar characteristics to the
offshore field developments.
In Trinidad there are excellent outcrop and producing field analogs of
deltaic
systems. Preliminary outcrop investigations have established there was
decreased accommodation space during deposition of the Pliocene Morne L'Enfer
Formation. In the Lower Morne L'Enfer member there was incision and subsequent
deposition of sediments within fluvial to estuarine channels within a
deltaic
setting, probably not unlike the present-day Orinoco. A major transgression
inundated the succession followed by a regression and deposition of
tidally-influenced
deltaic
deposits (Upper Morne L'Enfer). The transition marks
a decrease in basin accommodation space, with progradation of the
deltaic
facies
basinward. Outcrop work on fluvial to estuarine channels within this
deltaic
system can be applied to understanding of complex stratigraphic and
architectural analysis of analogous offshore Nova Scotia reservoirs.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005