Oil and gas wellbore leakage in Canada: key reporting uncertainties and measurement knowledge gaps
Bibliographic record
Abstract
Depleted oil and gas formations and associated wells can be exploited for use as energy or carbon dioxide storage infrastructure. However, a loss of wellbore integrity can result in the uncontrolled migration of fluids out of the well, risking groundwater contamination and releasing greenhouse gases (e.g., methane, carbon dioxide, hydrogen) into the atmosphere. In Canada, emissions specifically related to wellbore integrity and subsurface-based leakage have been monitored, measured, and reported by the oil and gas industry for more than a decade, resulting in some of the largest datasets to track such wellbore emissions. While these reporting systems were not necessarily designed to track methane emissions, both the provincial and federal governments nevertheless use these data to estimate methane emissions associated with subsurface wellbore leakage. Moreover, incomplete reporting by the industry has resulted in highly uncertain methane emission magnitudes, and attempts by federal and provincial governments to resolve these issues yield emission estimates varying by more than a factor of two. Further, poorly understood emission mechanisms are likely to yield even more uncertainty in total emissions from wellbore leakage.In this presentation, we illustrate the highly uncertain nature of methane emissions due to subsurface wellbore leakage in Canada using industry-reported data for the provinces of Alberta and British Columbia, regions covering more than 80% of crude oil and 95% of natural gas production nationally. We illustrate the sensitivity of these methane emission estimates using a variety of assumptions employed by the different governments for incomplete data, highlighting the key knowledge gaps for this source of emission. The different assumptions result in estimates varying by a factor of 3, and more troublingly, connotate fundamentally different understandings about wellbore leakage causes, sources of fluid, and progression of emission rates over time. We make initial recommendations for wellbore leakage monitoring and measurements to improve Canada’s methane quantification but with more broad applicability for monitoring well fluid leakage more generally.
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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 | 0.021 | 0.100 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.007 | 0.026 |
| Science and technology studies | 0.004 | 0.002 |
| Scholarly communication | 0.006 | 0.002 |
| Open science | 0.004 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| 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".