Stratigraphic Modeling of a Mix Siliciclastic-Carbonate System in A Passive Margin Setting: The Hettangian–Cenomanian Interval of the Shelburne Subbasin Area — SW Nova Scotia 2011 PFA Expansion

Abstract

As part of its ongoing projects on hydrocarbon resources assessment, the Department of Energy and the Offshore Energy Research Association (OERA) have published in 2015 an integrated exploration study which is an expansion of the 2011 Play Fairway Analysis (PFA). In this context, a forward stratigraphic model was generated to reproduce the alternating carbonate-siliciclastic deposits of Hettangian to Cenomanian age present in the Shelburne Subbasin. The sedimentary cover of this basin can reach 15 kilometers with basal Triassic synrift deposits overlain by a thick salt cover and Jurassic to present-day sediments. The stratigraphic model was performed using DionisosFlow® and contains 70 × 50 cells with 4 × 4 km of cell size covering 56000 km². Four major tectono-sedimentary events were reproduced by this model spanning 106 My. A Hettangian – Callovian event characterized by the onset of a carbonate platform at the position of the present-day shelf break. The backreef area was dominated by aggrading shallow marine/continental deposits. An Oxfordian – Tithonian event corresponding to the Jurassic Shelburne Delta prograded basinward supplying sandy sediments to the turbiditic systems in the basin. The distribution of depocenters in the shelf and basin area was strongly impacted by salt tectonics during this period. A sensible decrease on the clastic supply and a reactivation of the carbonate sedimentation on the shelf marked the final stage of this event during the Tithonian MFS. An episode of aggradation of carbonate deposits on the shelf and siliciclastic deposits at the backreef position took place during the Upper Tithonian to Valanginian period. A new phase of deltaic progradation was active during the Valanginian to Cenomanian period. This episode corresponds to the Cretaceous Shelburne Delta that mostly provided an important volume of potential reservoir facies to the basin area mainly represented by clastic and carbonatic turbidites. The model was calibrated using 2D seismic data and wells Bonnet P23 and Mohawk B93. The modeling results not only allowed a detailed 3D reconstruction of the margin evolution through time but also a prediction of the geometry and extension of reservoir facies in the still unexplored slope and basin areas. Facies distribution maps extracted from this model provided the stratigraphic framework for a petroleum system model generated for this promising new frontier basin (SW Nova Scotia 2011 PFA Expansion companion abstract).

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016