Leakage Risk Assessment in Rollover Structures of the Sable Subbasin, Offshore Nova Scotia: Implications for CCS
Bibliographic record
Abstract
Summary On the Scotian Margin, most of the successful commercial gas discoveries occur in simple closures within rollover structures of the Sable Subbasin where they have been produced from the high net-to-gross Missisauga Formation reservoirs. In the absence of the simple closure in this stratigraphic interval, a favorable juxtaposition of strata with the presence of extensive thick shales play a role in guaranteeing the success of key reservoirs that have been intercepted by faults. This paper uses a 3D geocellular model of two Structure drilled offshore Nova Scotia, populated with key reservoir parameters to demonstrate potential risks associated with fault leakage in the rollover. Using a previously constructed static model taken to dynamic modelling in these structures, a hypothesis that the residual saturations on logs will match the residual saturations in the dynamic models and will correspond to large water tests with very little gas is tested. Results from the dynamic modeling demonstrate an upward and outward cross-fault, stair stepping migration of gas through the reservoirs in the high net-to-gross shallow to intermediate sections of one of the structures after a minimum of 25 to 50 years of steady injection and equilibration. Post simulation, the presence of some residual gas saturation after the injection and equilibration phase supports initial observations of upto 50% gas saturation from log analysis of key reservoirs. In the other modelled structure, there is very little movement of residual fluids across the fault when geomechanical modelling is explored. In conclusion, results of the dynamic modelling confirm that residual trapping holds some significance in the sequestration of CO2 in faulted rollover anticlines where fault leakage may be a risk. Modelling applications done on the Rollover Structures in this study may be applicable to prospective margins where CO2 sequestration in rollover anticlines is being considered such as the Brazilian Margin and its conjugates in the Southern Atlantic.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".