Subsurface Migration of Methane From Oil Sands Thermal Recovery Operations
Bibliographic record
Abstract
Abstract Steam injection into oil sands reservoirs for bitumen extraction leads to the in situ generation of gases (mainly methane). Many oil sands formations have permeable cap rocks that may allow these gases to migrate to the overlying formations and pose environmental challenges to the groundwater. We present a detailed analysis of the long‐term fate of the in situ generated gases over the course of thermal oil recovery operations. The impacts of capillary barriers on upward migration of the in situ generated gases are quantified. Our findings reveal that the upward migration of gases over a 100‐year period in formations with continuous flow barriers with a permeability of less than ∼1 × 10−18 m2 is negligible. However, for formations with discontinuous flow barriers, the migrated gas can potentially leak to the surface depending on the capillary entry pressure of the preferential pathways (e.g., sand layers). In this case, the upward migration is primarily controlled by high permeability pathways. It was found that the migrated gas is effectively trapped by the residual and dissolution trapping mechanisms, and the gas migration to the overlying formations is prevented or significantly reduced by capillary pressure of sand layers. The results indicate that the migrated gas to the shallow groundwater is primarily comprised of methane and is free of CO2 and H2S. These results provide valuable insights into the long‐term fate of these gases in thermal oil recovery operations. They also offer potential opportunities for the development of regulatory frameworks and screening considerations for caprock/seal integrity/risk assessments.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".