Plug Cementing Stability
Bibliographic record
Abstract
Abstract Off bottom plugs are set in both well drilling (kick-off plugs) and in well decommissioning (abandonment plugs). In both cases a dense fluid (cement slurry) is placed over less dense well-bore fluids. In the case of kick-off plugs, viscous pills are commonly used, which can help stabilize this mechanically unstable situation. Abandonment plugs however are often set on top of the freshwater that is used to clean the well prior to abandonment. This is the current practice for many wells in Northwestern Canada. It is a mystery how such cement plugs are able to stay in place for a time sufficient for the cement to thicken and hydrate, but field evidence suggests they do. In this paper we explore the mechanically unstable scenario of a heavy yield-stress fluid placed on top of a less dense Newtonian fluid in a cylindrical pipe, dimensionally scaled to represent an off-bottom plug. We present details of the experimental setup and its calibration. We then explore the buoyancy-driven exchange flows that occur in transitional parametric regimes between flow and no-flow states, by using both computer modelling and physical experimentation. 3D numerical simulation, using a Volume of fluid method, is carried out to capture the interface between the fluids. The 3D model provides us with a more detailed analysis of the concentration and velocity profiles, along with comparisons to snapshots of the experimental results. The aim is to explore the phenomenology of these unstable flows and be able to estimate timescales of the destabilization. Preliminary results are presented.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".