Asphaltene Deposition and Heavy Phase Accumulation in a Vertical Capillary Tube
Bibliographic record
Abstract
Asphaltene deposition is a long-standing flow assurance issue typically modeled as particle deposition. In recent laminar horizontal flow experiments with n -heptane diluted bitumen, it was demonstrated that the asphaltene deposition mechanism changed from particle deposition at room temperature, where asphaltenes precipitated as glassy particles, to heavy phase accumulation at 130 °C, where a liquid asphaltene-rich phase formed. The purpose of this study is to determine if and how the deposition and flow behavior change in vertical versus horizontal flow for the same fluids and conditions. As in the previous study, the mechanisms were assessed at 50 and 130 °C in laminar flow through a 1.75 mm capillary tube using mixtures of bitumen and n -heptane with n -heptane contents from 65 to 90 wt %. However, in this case, the tube was oriented vertically with an upward flow. The pressure drop was monitored during the flow period, and the mass and location of the deposit were measured at the end of each experiment. Experiments were performed for capillary tube lengths of 3 to 30 cm and flow rates of 2, 4, and 8 cm 3 /min. It was confirmed that the mechanism for flow disruption changed from particle deposition below the glass transition to heavy phase accumulation in the multiphase flow regime above the glass transition. In the glassy particle regime, porous annular deposits occurred with more rapid cycles of blockage and blowout than with horizontal flow. In the liquid droplet regime, core-annular flow occurred, with the heavy phase accumulating in the annulus and appearing to undergo cycles of annular and slug flow. The behavior was analogous to the stratified flow observed in the horizontal configuration, but with more frequent cycles. The results suggest that, in the liquid droplet regime, flow assurance may better be evaluated as a multiphase flow issue rather than a deposition issue.
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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 | 0.000 |
| 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 | 0.001 |
| 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".