Nonequilibrium Exsolution Kinetics of Hydrocarbon Solvents in Heavy Oil
Bibliographic record
Abstract
Nonequilibrium exsolution kinetics of methane and propane in heavy oil were studied through visual experimentations and continuum simulations. Experimentally, novel Constant Composition Expansion (CCE) tests, combined with a micromodel to visualize the bubbly oil flow, were fulfilled in pressure–volume–temperature (PVT) cells. Two schemes were applied, namely, constant volume extraction (CVE) and stepwise pressure depletion (SPD). From the pressure measurement of CVE, methane first went through a pressure-declining period due to hysteresis of exsolution and later a pressure-maintaining period under a balance between exsolution and volume expansion rate. Meanwhile, the pressure of the propane system dropped rapidly and rebounded back to a constant pressure for a long period of time due to a higher solubility than methane. Compared with equilibrium state, the solvent exsolution of both live oils were always under nonequilibrium. Bubbly oil flow was visually observed to determine the range of pseudobubble point pressure. From the volume expansion behavior from the SPD tests, both methane- and propane-based live oil systems present a close-to-linear relationship between volume and time at each pressure drawdown level before reaching equilibrium. This facilitates the quantification of exsolution rate under given pressure. Numerically, a simulation platform to calculate nonequilibrium exsolution kinetics has been built. The feasibility of the simulator is verified through simulating literature data with various pressure data ranges. The exsolution rates have been achieved by history matching the CVE and SPD tests. For CVE tests, methane shows a higher exsolution rate (1 × 10 –4 to 1 × 10 –2 min –1 ) than propane (1 × 10 –6 to 1 × 10 –3 min –1 ) under the same volume expansion rate, indicating a higher tendency to exsolve and form foamy oil. Propane tends to stay in heavy oil due to high solubility. The exsolution rates of the stable-pressure period present a power relationship with volume expansion rate for both live oils. For SPD tests, methane presents a similar range of exsolution rates (1 × 10 –5 to 1 × 10 –4 min –1 ) as propane under similar P / P sat ratios with pre-existing free gas phase. Compared to tests conducted by a sudden pressure drawdown scheme, pre-existing gas cap yields lower exsolution rates due to smaller chemical potential between phases. SPD tests also verify faster exsolution kinetics for methane than propane.
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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 | 0.000 |
| 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".