Structural Restoration and 2-D Basin Modeling in Fold and Thrust Belts – A Case Study From Western Newfoundland

Abstract

The early Paleozoic fold and thrust belt on the west coast of Newfoundland hosts a frontier petroleum system that has minor production and several shallow wells with light oil shows. The basin sits at the structural front of the northeastern Canadian Appalachians, recording the complex tectonic history of Ordovician to Devonian shortening events. During the Taconian (Ordovician) and Acadian (Devonian) orogenies, westward thrusting imbricated continental slope and rise deposits, creating thrust sheets that repeat Lower Paleozoic strata. We present two-dimensional (2D) basin models to assess the thermal evolution, transformation, migration, and accumulation of hydrocarbons.

Two viable source rocks for this petroleum system have been identified in the Cow Head Group hosted in distal continental slope and rise deposits, with TOC concentrations of up to 10.35 wt.% and a type I/II kerogen with high hydrogen index (HI) values of over 840 [mg HC/g TOC].

This initial investigation presents a 2D petroleum basin model approach including a structural restoration of the fold and thrust belt. The model is calibrated with petrophysical property logs collected from two well, Seamus #1 and Finnegan #1 drilled in 2010. Geochemical data from outcrop samples and oil seeps were used to characterize the source rock quality. Maturity data from pyrolysis analysis are used as additional calibration data.

Our 2D model for the area shows that kerogen transformation starts prior to the Acadian reverse faulting. Maturity data from outcrop samples indicates that a substantial amount of overburden (approximately 2 km) was present after the Acadian orogeny. This 2D model gives an in-depth understanding of the evolution of the petroleum system in western Newfoundland and contributes to a better understanding of hydrocarbon generation and migration in fold and thrust belts in general. Understanding these critical elements in a petroleum system context can in turn provide proper risk assessment for future exploration efforts in fold and thrust belts.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018