context of hydrocarbon systems in the Hudson Bay. Basin. 2. The reefs are directly on top of TOC-rich, Type I-IIs oil- prone source rock. 3. The reefs are locally ...
Upper Ordovician reefs in the Hudson Bay Basin: Porosity evolution and hydrocarbon charge Denis Lavoie1, Ariane Castagner2, Omid Haeri Ardakani1 and André Desrochers2 1- Geological Survey of Canada 2- Ottawa University
Outline The Hudson Bay Basin – geological setting and hydrocarbon exploration history Source rocks Potential reservoirs Upper Ordovician reef of the Red Head Rapids Formation Diagenetic evolution – petrography-geochemistry-fluid inclusions
Evidence for hydrocarbon migration On-going research and conclusions
The largest intracratonic basin in North America
Regional setting and historic background
46 000 linear-km of industry seismic (1970’s) 40 000 linear-km of GSC seismic (1980-1990) 5 wells in the Bay 1 well Akpatok Island 3 wells Manitoba 1 well northern Ontario
Devonian to Upper Ordovician shallow marine platform carbonates, shales and local bioherms ------------------------------variably thick, restricted marine evaporites ------------------------------thin, widespread organic-rich shales -------------------------------thin sections of coastal plain sandstones
Lithostratigraphy U3
U2 U1 Dietrich et al (2012, SEG)
Basin geometry
New seismic interpretation 3 major unconformities Ordovician-Silurian: U1 Upper Silurian-Lower Devonian: U2 Middle Devonian: U3
Research highlights 1. Evaluate the reservoir potential of the reef facies in the Upper Ordovican Red Head Rapids Formation in the context of hydrocarbon systems in the Hudson Bay Basin 2. The reefs are directly on top of TOC-rich, Type I-IIs oilprone source rock 3. The reefs are locally highly porous with report of dead oil and bitumen in pore space
Massive reef – Southampton Island
180 m
500 m
Crudely-bedded
Interpreted sub-surface presence
Top Silurian Top Ordovician
Pore and fracture-filling bitumen Very porous
Ordovician – Silurian unconformity
Facies Two main facies: Cementstones
Boundstones
Calcimicrobes
5 mm
Laminated automicrite
5 mm
Paragenetic succession
Cement succession – marine isopachous
Cement succession – marine botryoids
Cement succession – dissolution
Cement succession – late (post dissolution) cements
Cement succession - bitumen
Cement succession - bitumen
Geochemistry – Stable isotopes
Fluid inclusions – work in progress
Late fluid composition
Hydrocarbon generation and migration ? Abundant, potential oil slicks in the area as determined through RADARSAT images
Upcoming research – the hunt for pockmarks Seabed mapping in strategic areas in Foxe Channel and Hudson Strait
Upcoming research – refining thermal history Rock Eval (black shales): Tmax: 421 - 432˚C (Lavoie et al., 2013, OF 7363) immature Apatite Fission Track (basal sandstone): 65 - 85°C (Pinet et al., 2016, OF 8110) early mature Fluid inclusions (late cements, in progress): 75 - 150°C oil window Clumped isotopes (late cements): in progress
Conclusions 1. The Upper Ordovician reef in the RHR Formation mainly displays boundstone and cementstone microfacies with abundant synsedimentary (aragonite – now calcite) and post-dissolution (calcite) cements. 2. Bitumen is present in fracture and dissolution pore spaces 3. Late cement phases are depleted in both δ18O and δ13C 4. Fluid inclusions are mostly saline (>12%) and high temperature (2 groups; one average of 115°C another at 80°C) 5. Possible local circulation of fault/fracture controlled hydrothermal fluids – no pervasive alteration noted
