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