Multiphase flow modelling of gas migration from a hypothetical integrity-compromised petroleum well in the peace region of North-eastern British Columbia, Canada
Bibliographic record
Abstract
• This study explores the bifurcated impact of fugitive methane from petroleum wells on groundwater and the atmosphere. • Well cement quality, release depth, and heterogeneity play key roles in controlling fugitive gas migration. • Our work introduces and/or employs novel parameters for a comprehensive assessment of fugitive gas containment or pollution strategies. • The findings highlight the importance of including gas migration influential parameters in risk assessments for integrity-compromised wells. • The insights gained offer valuable input for designing effective greenhouse gas control strategies in geoenergy applications. Well-integrity failure occurs in a small subset of petroleum wells, resulting in release of fugitive gas into intersected geologic formations. Released fugitive gas from geoenergy systems is a growing environmental concern that can contaminate groundwater aquifers and emit greenhouse gases (GHGs) to atmosphere. Currently, the roles of well-cement quality and properties of intersected geologic formations on the environmental outcomes of well-integrity failure is poorly understood. To advance understanding, we numerically modelled a hypothetical fugitive methane release from a petroleum well intersecting the Sunset Paleovalley aquifer system in Northeast British Columbia, Canada. We simulate a 10-year release and migration of fugitive gas into a two dimensional, two-phase, two-component advective flow field with the subsurface properties informed by field and laboratory data. We evaluate the effects of cement quality, gas release depth, and geologic heterogeneity on fugitive-gas containment or emission by defining and/or evaluating three key numbers: a) emission-retention ratio (ERR), b) well integrity index (WII), and c) fugitive gas mobility ratio (MR) over relevant spatiotemporal scales. We show that ERR and WII capture the bifurcated impacts of fugitive gas from petroleum wells, including groundwater contamination and atmospheric emissions. A WII close to one reduces vertical fugitive-gas migration along the well bore, fosters lateral migration into intersected geologic materials and significantly limits GHG emissions to atmosphere. MR and ERR values show fugitive-gas migration and fate are primarily controlled by the casing annulus cement quality, particularly when fugitive gas is released at shallow depths. We conclude that the quality of petroleum-well cement is among the parameters controlling the migration pathways, impacts, and fate of fugitive-gas release.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".