Assessing groundwater vulnerability to shale gas activities in the Sussex area, southern New Brunswick
Bibliographic record
Abstract
A project studying potential hydrocarbon migration through natural pathways or fracking-induced fractures from deep (~2 km) Carboniferous shale or tight sand units to shallow aquifers was initiated in 2015 in the Sussex area, southern New Brunswick. The study area includes the McCully gas field that has been in production since 2001 and the Elgin field that is investigated for its condensate potential. Because the intermediate zone (IZ) located between shallow aquifers and units targeted for hydrocarbon production is poorly characterized, this project relies on the integration of data from different earth science disciplines, including geology, geophysics, geomechanics, hydrogeology and water and rock geochemistry. Fieldwork in 2018-2019 included the drilling of two observation wells, borehole geophysics, and groundwater monitoring. Data collected during this 4-year project and their interpretation provided no evidence for the presence of large-scale connections between gas reservoirs and shallow aquifers in this study area. On the contrary, the IZ seems to provide an efficient barrier protecting the shallow aquifer from the potential upward migration of fluids originating from deep hydrocarbon reservoirs. This conclusion integrates the interpretations derived from the geomechanical study, from the geophysical and geological analyses of the structural context and from the geochemical baseline study. Although large-scale upward fluid migration is considered very unlikely, evidence of some upward migration over a few hundred meters was found based on old, evolved groundwater observed in two of the shallow (50 m) observation wells. This water indicated a contribution from evaporites from a relatively shallow salt structure (~250-300 m), whose chemical components are assumed to have been transferred to the active groundwater flow zone by diffusion. Also, regular monitoring of several shallow wells helped ascertain the source of methane in groundwater when individual samples provided ambiguous results.
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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 | 0.001 | 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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".