Experimental investigation of the dynamics of displacement flow in vertical wavy annuli across varied flow conditions
Bibliographic record
Abstract
Effective primary cementing is essential for ensuring well integrity, extending the operational life of wells, and minimizing environmental risks from leaks or failures. For over five decades, researchers have studied the displacement of drilling mud by cement slurries in annuli, with a focus on irregular wellbore geometries such as eccentricity, ovality, and rugosity. Among these, eccentricity is the most extensively studied irregularity due to its significant impact on mud removal and displacement efficiency. Studies show that flow rates, viscosity ratios, and density ratios strongly influence displacement stability in both horizontal and vertical eccentric annuli. For example, Malekmohammadi et al. [2] observed stable traveling wave displacements in highly eccentric configurations, while Renteria and Frigaard [3] examined flow instabilities. Zhang et al. [4] demonstrated that higher buoyancy numbers and lower Reynolds numbers stabilize the interface and reduce dispersion in vertical displacements. Research on other irregularities, such as washouts and obstructions, is comparatively limited. Skadsem et al. [5] investigated washout effects and found that residual fluid accumulation depends on eccentricity and inclination. Mitishita et al. [6] studied displacement of non-Newtonian fluids in eccentric annuli with obstructions, showing that eccentricity plays a dominant role. Additional studies revealed that consolidated cuttings beds primarily have localized effects on displacement flows, underscoring the need for further investigation into less-explored irregularities.Renteria et al. [7] and Sarmadi et al. [8] took a different approach, studying annular displacement flows in geometries derived from real caliper readings. Fourier analysis of borehole diameter variations revealed dominant lower-frequency patterns with superimposed high-frequency roughness. Inspired by this, we designed and constructed a wavy annulus by applying a Gaussian moving-average filter to caliper data from a real wellbore. This smoothed data produced a semi-sinusoidal wavy pattern, which we used to create a wavy annulus and mounted it onto the flow loop we have already had in our lab. Our experiments investigated Newtonian fluid pairs across a range of Reynolds numbers, buoyancy numbers, and viscosity ratios, focusing on how the wavy geometry influences displacement flow dynamics in a vertical orientation. Results demonstrate that the irregular geometry significantly impacts the stability and dynamics of the displacement front, offering valuable insights into challenges encountered during primary cementing in real-world scenarios. By bridging the gap between idealized models and practical conditions, this study provides a deeper understanding of displacement flows in irregular wellbores.
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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 | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".