Capillary Number in Heavy Oil Solution Gas Drive and Its Relationship with Gas-Oil Relative Permeability Curves
Bibliographic record
Abstract
Abstract Many heavy oil reservoirs under solution gas drive show a significant increase in productivity. Different mechanisms have been postulated to explain the high recovery factors observed in the field. Lately, a widely accepted cause of this increase in productivity is the foamy oil flow, which dramatically decreases the gas relative permeability. However, it still remains inadequately understood. It has been reported that the foamy flow effects observed in the laboratory depletion tests are strongly affected by depletion rate. This observed rate effect has been attributed to the influence of the pressure depletion rate on bubble nucleation. However, the researchers have mostly overlooked the capillary number, which increases significantly with increasing depletion rate. The goal of this study was to examine this capillary number effect in heavy oil reservoirs and its relationship with gas-oil relative permeability curves. A number of experiments were carried out on a two-meter long sand-pack to determine the conditions required to produced more oil under solution gas drive. The experimental data were matched on a commercial black oil simulator to determine the relative permeability curve under varying flow conditions and at different capillary number. The experimental results show that the oil produced was a unique function of capillary number and beyond a critical capillary number no additional improvement in the recovery factor was observed. An examination of the changes of capillary number during the test provides insight into the gas-phase build up during solution gas drive and the resulting production behavior. It was also found that oil relative permeability increases and gas relative permeability decreases with increasing capillary number. At high capillary number, relative permeability ratio remains very low up to higher value of gas saturation. The results from this research suggest that the conventional correlations of gas-oil relative permeability should incorporate the effect of capillary number in order to improve the prediction of foamy oil flow mechanism.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".