Conventional Reservoirs can be regarded as oil and gas accumulations that will naturally flow to surface once they are intersected by a well. These types of reservoirs generally have characteristic high porosity and permeability. This means that oil and gas can accumulate within the reservoirs and in turn is capable of flowing out of the reservoir once it is subjected to an open conduit with adequate pressure differentials. In summary, conventional reservoirs can generally produce hydrocarbons without any sort of stimulation.
Unconventional Reservoirs on the other hand are reservoirs that do not naturally or economically flow to surface once intersected. This can be for a multitude of reasons including low permeability of the rock matrix, high viscosity of the hydrocarbon, and closed faults or fractures within a reservoir that cause local barriers to flow. These types of reservoirs require additional work to economically extract hydrocarbons. On Newfoundland’s west coast, the unconventional potential for BSE consists of low permeability oil shales. These rocks are believed to require hydraulic fracturing in order to facilitate production. The process of hydraulic fracturing involves pumping a fluid of 99.51% water and sand into the reservoir at high pressures so as to open existing and create new fractures in the rock which act as a conduit for the otherwise immobile hydrocarbons within the formation.
Compressional vs Extensional
East of the Appalachian Structural Front (ASF) is a Compressional Regime. West of the ASF is Extensional.
Conventional and Unconventional Opportunities
With BSE’s large land holding of 1.33 million acres in western Newfoundland, it should not be a surprise that there exist multiple prospective oil and gas play types. BSE believes this multitude of play concepts diversifies its exploration portfolio and in some cases creates stacked drilling targets.
Currently BSE’s core focus is on two specific play types:
- Conventional, oil and gas in the Extensional Ordovician Dolomite (Carbonate Platform) play, west of the ASF;
- Conventional, oil and gas in the Carboniferous clastic rocks onshore in the BSE Exploration Permits in Deer Lake Basin;
Extensional Ordovician Dolomite Play
The extensional Ordovician Dolomite Play is analogous to that of the compressional play in that the target remains the St. Georges Group Carbonates, however, the play lies west of the Appalachian Structural Front and as such did not experience the same tectonic activity related to the Appalachian Orogeny. As a result, the structural traps consist of horst blocks and tilted fault blocks as is common in many extensional basins. The early formation of the thick skinned extensional faults are due to the same early Paleozoic rifting of the Iapetus Ocean and the subsequent migration of a foreland bulge during the Taconic orogenic event as the strata to the east of the ASF and as such are thought to have similar enhanced reservoir quality in the footwalls of these faults.
Depiction of present day structural framework from west of the ASF to east of the ASF. Notice the displacement on the faults moving from net normal to net reverse (Enachescu, 2013).
Extensional Carboniferous Clastic Alluvial Fan and Meandering Stream Play
BSE currently has two exploration permits in the Deer Lake Basin totalling almost 160,000 acres. This basin is an extensional strike-slip basin that formed subsequent to the Appalachian Orogeny. The basin fill is lacustrine and consists primarily of clastics. One of the primary targets within the basin is the North Brook Formation, which has significant thickness. Prospectivity lies in the conglomerates and sandstones of alluvial fan and meandering stream deposits that appear to have filled the basin from both sides. The Deer Lake Basin has a lacustrine source rock as well as several flower structures at its base around which structural traps are thought to have formed.
Seismic Interpretation showing interpreted flower structure and associated North Brook deformation. (Wright, J.A., B. H. Holfe, G.S. Langdon, and G.M. Quinlan, 1996)