Sedimentology, depositional environment, and reservoir properties of the Silurian Interlake Formation, southern Saskatchewan
Bibliographic record
Abstract
The Interlake Formation, located in southern Saskatchewan, dates to the Early Silurian period and was deposited on the northern shelf of the Williston Basin. The formation is characterized by dolostone lithology and spans southwestern Manitoba, eastern Alberta, and neighbouring U.S. states. Late Ordovician – early Silurian glacio-eustatic sea level drop resulted in a stratigraphic temporal gap between the Upper Ordovician Stonewall Formation and the Lower Silurian Interlake Formation. Cores, wireline logs, and petrographic information were gathered from 30 wells and analyzed from the research area. The results indicate that the formation can be categorized into three informal members: lower, middle, and upper. The lower member comprises bioturbated dolostone lithofacies and minor reddish argillaceous dolomudstone. The latter serve as marker beds that facilitate correlation within the study area. The middle member consists of thickly laminated, bioclastic dolomudstone characterized by marine fauna. The upper member is distinguished by diverse intraclastic and sparse/nonfossiliferous dolostone facies, subordinate anhydrite layers and nodules. Seams of argillaceous dolomudstone at the millimetre scale are also visible. The core and petrographic analyses of the formation allow the identification of six lithofacies: Lf1-Lf6. The lithofacies properties, sedimentary structures and textures, fossil content, and lithofacies associations suggest that the formation was deposited in a shallow marine environment, ranging from intraclastic and bioclastic dolopackstone/grainstone subtidal shoals to landward lagoonal (restricted) environment to peloidal and bioclastic dolomudstone/wackestone intertidal and supratidal mudflat settings. The diverse lithofacies are organized in meter-scale cycles of shallowing-upward successions, believed to be influenced by Milankovitch Sea level fluctuations. The lithofacies configuration of the analyzed stratigraphic interval exhibits distinct vertically stacked rhythmic units of basal subtidal lithofacies (Lf5, Lf3) transitioning to restricted lagoonal/intertidal (Lf4) to supratidal mud-flat deposits (Lf2, Lf1, and Lf6). The examination of cyclicity plots for these rhythmic units indicates elevated 4th to 5th-order Milankovitch cycles, which can be categorized as a stack of 3rd-order depositional cycles. The 4th-order cycles exhibit a strong correlation with the Silurian cyclothems, resulting from slow basin subsidence and eustatic sea level fluctuations. The identified diagenetic products and paragenetic sequence from core logs, petrographic, and SEM analysis include micritization and micrite envelope, various instances of calcite cementation, dolomitization, anhydrite cementation, dewatering and dissolution, compaction fracturing, stylolite formation and pyrite filling. The principal diagenetic processes influencing the porosity evolution of the Interlake Formation include cementation, compaction, dolomitization, and dissolution. The primary and secondary porosity of the various lithofacies of the Interlake Formation encompasses intercrystalline, fracture, vuggy, intracrystalline, and fenestrae porosities. Variations in porosity and permeability among the lithofacies of the Interlake Formation arise from differing degrees of porosity-destruction and porosityenhancement characteristics. The Lower Interlake demonstrates good porosity (average 12%) and permeability (average 15.9 millidarcies), and the Middle Interlake displays moderate porosity (average 5%) and permeability (average 5.2 millidarcies). In contrast, the Upper Interlake reveals comparatively low porosity (average 3%) and higher permeability (average 28 millidarcies). Thus, the lower member shows the best reservoir potential (conventional reservoir where f>5%), the middle member is at the boundary between conventional and unconventional reservoirs, and the upper member is an unconventional reservoir (f<5%). The Interlake Formation is a candidate for potential CO2 sequestration.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".