Relationship between hydrogen sulphide (H2S) distribution and regional burial/uplift history in the Lower Triassic Montney Formation, northeastern British Columbia, Canada
Bibliographic record
Abstract
Understanding a basin’s thermal history is essential when examining past and current fluid distributions. Knowledge of the origin of non-hydrocarbon gases, including hydrogen sulphide (H2S), aids in understanding the complex organic-inorganic interactions that control basin evolution. This study provides a preliminary workflow to estimate the regional burial and uplift/erosion history of the Lower Triassic Montney Formation using a Lower Cretaceous Mannville Group vitrinite reflectance dataset. The calculated maximum burial is a first-order thermal maturity proxy. Results show variations in regional Montney burial and uplift. Specifically, increased uplift/erosion in the central area of the Montney and relatively less uplift and erosion toward the southern extent of the play. To better understand controls on the highly variable H2S distribution, identified facies are constrained within a detailed stratigraphic framework in northeastern British Columbia, highlighting the vertical and lateral facies heterogeneity (Township 79-81 and Ranges 18-14). Additionally, local structural lineaments may have influenced fluid migration. Sulphate-rich fluids migrating through fractures may preferentially enter laterally permeable units. Due to regional burial history variations, fracture cementation is likely non-uniform, meaning not all fractures are fluid conduits. Depending on the location within the basin, a once permeable unit may now have diagenetic cementation, creating lateral permeability variations for sulphate-rich fluid migration. The current Montney Formation H2S content predominantly results from in situ thermochemical sulphate reduction (TSR). The regional burial variations result in thermal differences, implying that TSR should also be non-uniform across the Montney. Upper Montney H2S concentration increases eastward within the study area, likely due to up-dip migration through permeable coarser-grained siltstones and trapping due to stratigraphic pinch out. Additionally, the elevated H2S is likely influenced by extraformational factors, including eastward thinning of the Middle Triassic succession, bringing the evaporite-rich Charlie Lake Formation into proximity with the Montney. Moreover, the Sunset Prairie Formation directly overlies the Montney and has an erosional edge that correlates to elevated Upper Montney H2S. Both relationships may lead to more significant amounts of sulphate minerals in the east supplying the sulphate required to generate H2S via TSR.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
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".