New Insights into the Interfacial Phenomena during Miscible Displacement by Hydrocarbon Solvents and CO2 in Heavy Oil Reservoirs
Bibliographic record
Abstract
Abstract Injection of solvents (hydrocarbons in liquid and gas form or CO2 and their combinations) is an alternative method for heavy and extra heavy-oil recovery where thermal methods cannot be applied, like in thin reservoirs, wormholed reservoir after-CHOPS (cold heavy-oil production with sands), or fractured reservoirs. The solvents normally exist in their liquid or supercritical phase under reservoir conditions and may not be miscible with heavy oil at first contact. Coupling with the fact that diffusion into highly viscous fluids tends to be very slow and an interface exists in the first contact of liquid solvent and oil, displacement by capillary imbibition may take place. This displacement eventually improves the contact area between oil and solvent and results in enhancement of the mixing process by diffusion. To understand this phenomenon and fully capture the interaction of solvent and heavy oil in different rock systems, experimental investigations were conducted using sandstone and limestone core samples. The samples were saturated with different types of oils (viscosities ranging between 14 and 170,000 cP) and the solvents tested were heptane, propane, decane, CO2, and naphtha. To maintain the pressure of propane and CO2 above the saturation pressure, a specially designed high-pressure imbibition cell was used and the imbibition-diffusion process was visualized through the glass window of the cell. The color of the mixture and the amount and the shape of produced oil over time was used to analyze the mass transfer and flow behavior qualitatively and quantitatively by observing the evolution of oil production from core samples that were saturated with heavy oil and then immersed into solvents. We observed that in the solvent/heavy oil system, where molecular diffusion is a slow process, a dynamic interfacial tension IFT exists, but vanishes over time; when the CO2 is in the non-wetting phase the capillary force acts to retain the oil in porous media. As the IFT is reduced, capillary force is weakened and gravity governs the process. Hence, the fluid saturation in the porous media is totally determined by density and viscosity difference. If the wettability of the rock is altered during the process from oil-wet to more CO2 wet, because of oil-rock interaction, then it is possible for the porous media to spontaneously imbibe CO2.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".