Oil Recovery Performance of Immiscible and Miscible CO<sub>2</sub> Huff-and-Puff Processes
Bibliographic record
Abstract
The recovery performance of immiscible and miscible CO 2 huff-and-puff processes for enhanced oil recovery (EOR) in a light crude oil sample was experimentally investigated. The minimum miscibility pressure (MMP) of the original light crude oil–CO 2 system was determined by means of the vanishing interfacial tension technique and found to be MMP = 9.18 MPa. Then, the solubility of the CO 2 in the light crude oil and oil swelling factor due to the CO 2 dissolution in the oil phase were determined at T = 30 °C and various equilibrium pressures ranging from atmospheric pressure to P eq = 12.55 MPa. Later, series of immiscible and miscible CO 2 huff-and-puff tests were designed and carried out at various operating pressures (i.e., P op = 5.38–10.34 MPa). The results of the experiments showed that for secondary CO 2 huff-and-puff tests performed at the operating pressures below the MMP, the ultimate oil recovery factor is quite low. It was also found that in immiscible CO 2 huff-and-puff (i.e., P op < MMP) scenarios, the oil recovery factor substantially increased as the operating pressure approached near-miscible conditions. The oil recovery factor almost reached its maximum value at operating pressure near MMP (i.e., miscible condition), and further increase of operating pressure beyond MMP did not improve the recovery factor at all. The tertiary mode of miscible CO 2 huff-and-puff was also examined, and it was revealed that the oil recovery is significantly improved after a waterflooding process. The oil recovery mechanisms during the CO 2 huff-and-puff were mainly recognized to be interfacial tension reduction, oil swelling, and extraction of lighter components by CO 2, especially during miscible CO 2 injections. In addition, the average asphaltene content of produced oil and the permeability reduction of the porous medium as a result of asphaltene precipitation were measured in each test. It was found that the amount of precipitated asphaltene in the porous medium as well as permeability reduction are considerably higher in near-miscible and miscible CO 2 huff-and-puff tests compared to those in immiscible cases. The compositional analysis of remaining oil from CO 2 huff-and-puff tests at immiscible and miscible conditions also showed that lighter components of oil are extracted by CO 2, leading the remaining oil to become heavier with greater amounts of heavy hydrocarbons (i.e., C 30+ ). However, it was observed that the extraction of lighter components during miscible injection processes is more predominant than that during immiscible injections, resulting in the production of higher quality oil.
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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 | 0.000 | 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".