Effect of Confinement on Gas and Oil Relative Permeability During CO2 Flooding in Tight Oil Reservoirs
Bibliographic record
Abstract
Abstract For Cardium tight sandstone reservoir and Monteny liquid rich shale reservoir, horizontal well with multi-stage hydraulic fracturing is applied to develop the oil underground. However, Primary recovery of tight oil reservoirs is still low even with horizontal wells and massive hydraulic fracturing. A CO2 flooding process is regarded as a promising technique for improving tight oil recovery. However, the gas-oil relative permeability during CO2 injection is not fully understood because the nanoscale pore confinement in tight oil reservoirs alters phase behavior of the reservoir fluid. In this paper, the effect of confinement on gas and oil phase behavior is investigated. Afterwards, the gas-oil interfacial tension and solubility parameter are analyzed, resulting in an alteration in relative permeability during CO2 injection without and with hysteresis. Results show that the relative permeability of oil and gas can be further increased by the confinement effect during CO2 flooding as the interfacial tension of gas-oil can be further decreased in a nanoscale pore. Furthermore, miscibility is enhanced by the confinement effect as the solubility parameters difference between oil and gas decreases. It is consistent with the reduction in gas-oil interfacial tension. In addition, the gas phase trapping caused by hysteresis effect is weakened by the confinement effect, resulting in a lower critical gas saturation and a better oil production during CO2 injection.
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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 | 0.000 |
| 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".