Using Lightweight or Low Viscosity Preflushes for Primary Cementing of Surface Casing
Bibliographic record
Abstract
Preflushes are often used as part of the sequence of fluids pumped in primary cementing. Usually two functions are served by preflushes: I) to wash the drilling fluid ahead, by a combination of turbulence and chemical reaction; II) to provide a chemically compatible spacer between the lead slurry and the drilling mud. In some cases a wash precedes a spacer, but often only a single preflush is used. We consider well parameters typical of surface casing cementing in North Eastern British Columbia. Using a two-dimensional model of annular displacement flows, we show that the wash concept is flawed. In particular, in a sequence of simulations varying from intermediate density to low density we show that the wash progressively advances ahead of the lead slurry, channeling rapidly up the wide side of the annulus. Even when fully turbulent, it is ineffective at displacing mud from around the annulus, invalidating the motivation of chemical cleaning through contact time. Furthermore, the advance along the wide side of the annulus drains the volume of fluid separating the cement from drilling mud. Thus, the idea that the wash provides a barrier between slurry and and mud is invalid.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".