Petrological insights into thermal maturity, source rocks, migration, diagenesis L.D. Stasiuk and N.S.F Wilson Natural Resources Canada Geological Survey of Canada

Thermal maturity – 2002-03 progress Reassess Vitrinite %Ro from Evenchick et al, 2002 (~ 160 samples). New Vitrinite % Ro and Tmax from Rock Eval for about ~ 200 samples.

Reassess Vitrinite %Ro from Evenchick et al, 2002

Petrology of Organic Matter and Rock Eval Evaluation of Potential Source Rocks Osadetz et al. have defined ‘Effective Petroleum Systems’ in Bowser Basin related to petroleum stains / shows proposed to come from: a Paleozoic carbonate marine source rock deposited in a mesohaline to hypersaline setting (for stains in Muskaboo Creek Assemblage at Tsatia Mountain); Mesozoic lacustrine – non-marine source rocks (for stains in Triangle zone) Mesozoic normal marine source rock in Richie Well stains (e.g. 6745’) and in stains near Bucking Horse & Spatsizi River intersect.

Aptian to Albian to Campanian Tango Creek Formation; Non-marine potential hydrocarbon source rocks

Aptian to Albian to Campanian Tango Creek Formation: non-marine potential hydrocarbon source rocks in triangle zone Black shales (44/89, 872-875/92 series) : Bowser Basin: 1.34 - 2.54, 8.4 % TOC just North of Kitchener Lake. Sustut Basin 4.7 % TOC, near Stikine River-Cullivan Creek crossing for source rocks in the mid-late oil window (0.90 to 1.2 %Ro vitrinite). Coaly partings: 60-70 % TOC

Rock Eval pyrolysis for Tango Creek, Triangle Zone and Sustut Basin (for Rocks with vitrinite %Ro > 1.0 – 1.5 and Tmax > 450 C – i.e. late oil window to condensate - dry gas

Rock Eval pyrolysis for Tango Creek Rock Eval pyrolysis for Tango Creek ?? for coals and black shales with vitrinite %Ro > 1.2-2.5 and Tmax > 480-560 C – i.e. condensate - dry gas

Terrestrial – cuticular organic matter in coals and shales Upper Jurassic to Upper Cretaceous deltaic deposits, Bowser and Sustut basins Tango Creek shales – 8 % Total Organic Carbon

Terrestrial – cuticular organic matter in coals and shales Upper Jurassic to Upper Cretaceous deltaic deposits, Bowser and Sustut basins

Aptian to Albian to Campanian Tango Creek Formation; Non-marine potential hydrocarbon source rocks – coals ? Vitrinite %Ro = 0.87

Aptian to Albian to Campanian Tango Creek Formation; Non-marine potential hydrocarbon source rocks – coals ? 875/92

Rock Eval pyrolysis for Skelhorne assemblage for coals and black shales with vitrinite %Ro of 2.6- 5.0 and Tmax > 600 oC – i.e. dry dry gas to sub-green schist

Recycled lacustrine Type I kerogen source rock clasts in Eagles Nest Assemblage (reworked from Muskaboo Creek ??)

Recycled lacustrine Type I kerogen source rock clasts in Eagles Nest Assemblage (reworked from Muskaboo Creek ??) Vitrinite %Ro 0.80-0.90. Fluorescent light White light

Recycled lacustrine Type I kerogen source rock clasts in Eagles Nest Assemblage showing Pediastrum like morphology (freshwater, e.g. lacustrine algae) Fluorescent light Modern

Some Pediastrum species also is characteristic of the littoral zone of oligotrophic waters

Crude oil generation from recycled lacustrine Type I kerogen source rock clasts in Eagles Nest Assemblage and migration of higher API oils in microfractures

High maturity recycled possible lacustrine Type I kerogen source rock clasts in Tango Creek, Eagles Nest and Todagin assemblage; Gas Zone, 1.0 to 1.4 %Ro

Recycled lacustrine Type I kerogen source rock clasts in Eagles Nest Assemblage (reworked from Muskaboo Creek ??) Evenchick et al., 2002 Some Pediastrum species also characteristic of the littoral zone of oligotrophic waters

Sedimentary petrology

EP-91-91 Calcite filled porosity with HC inclusions There are a few slides of EP-91-91 showing calcite cements, their dissolution, and generation of pore space in a single sample. PPL image of calcite cemented sandstone (dashed line highlights cements, which under UV are fluorescent) UV image showing calcite cleavage (highlighted by blue fluorescent HC inclusions, some 2 phase so can get temps). Probably Primary inclusions (since along cleavage BUT is a plane of weakness so could have filled when HC moved into the rock). Some pyrobitumen at edges of pores could be earlier than the later stage (should do Ro to confirm this). EP-91-91

EP-91-91 Pyrobitumen lining pores - dissolution - HC inclusions 1) Further into the sample the calcite is gone, and pyrobitumen lines open pores. Dissolution removes carbonate, some qtz precipitated as small grain overgrowths, and within pyrobitumen (somewhat euhedral grains). In this area typically a lot of 2ndry HC inclusion (blue F) around edges of detrital grains and along cleavege in carbonate grains. EP-91-91

EP-91-91 Leached Pore space PPL of larger pores and dissolution of detrital grains (looks like feldspar; 2 cleavage planes) highlighted by blue resin In UV see resin (red, colour balanced in ACDsee) and grain has loads of most likely 2ndry inclusion, all bright blue but nothing in pore space EP-91-91

EP-91-91 Calcite cements Pyrobitumen + HC Inclusions Pore space – Fewer HC incs The calcite has irregular edges and you can trace the dissolutions and filling with pyrobitumen (which suggests that we’ve see dissolution) rather than successive events. Also dissolution (resin impregnation) of detrital grain (not present where calcite cements are) suggest dissolution as well. This process could be beneficial if before major generation, but seem like this samples has seen quite a bit of HC so may post-date the major phase of petroleum generation. Still more to be done to tie things together. EP-91-91

These relationships are common in quite a few samples (inc These relationships are common in quite a few samples (inc. EP-89-101, EP-90-69 [py replaced by hem], EP-91-84 [V.strong in this sample] etc.) 1) Slide of pyrobitumen veinlets-stringers cutting the sample. Rare HC incs in the sample some bright vitrinite (talked earlier this week about this) 2) Hematite veinlets cross cutting the samples and pyrobitumen veinlets; Also hematized (oxidized) sulfides (reduced) within the sample post-pyrobitumen emplacement. Is this local or regional? Certainly is significant WRT the petroleum history. EP-89-101