Steam-Solvent Coinjection under Reservoir Heterogeneity: Should ES-SAGD be Implemented for Highly Heterogeneous Reservoirs?
Bibliographic record
Abstract
Abstract Expanding-solvent steam-assisted gravity drainage (ES-SAGD) is a widely-investigated alternative to SAGD, considering its potential to reduce thermal losses while enhancing bitumen recovery. However, most prior studies on ES-SAGD were limited to homogeneous reservoirs. This research presents a mechanistic analysis of ES-SAGD in heterogeneous reservoirs in terms of cumulative steam-oil ratio (SOR) as a function of steam-chamber size. Simulation case studies for SAGD and ES-SAGD with normal hexane are conducted for geostatistical realizations of two types of heterogeneous Athabasca-bitumen reservoirs. For the first type, shale barriers are oriented horizontally relative to the top and basal planes of the reservoir. For the second type, they are inclined and more representative of the middle McMurray member. The solubility of water in the oleic phase at elevated temperatures is properly modeled to ensure reliable comparison between SAGD and ES-SAGD. Results show that ES-SAGD is less sensitive to heterogeneity than SAGD in terms of cumulative SOR for simulations at 35 bars and 2 mol% solvent-injection concentration for a reservoir thickness of 20 m. On average, the reduction in SOR due to steam-solvent coinjection is simulated to be greater under heterogeneity. The margin of SOR reduction is greater in reservoirs with inclined shale barriers than in those with horizontal shale barriers. Analysis of simulation results indicates that the injected solvent tends to accumulate more significantly under heterogeneity, which enhances the mechanisms of ES-SAGD, such as dilution of bitumen by solvent and reduced thermal losses to the overburden. Tortuous hydraulic paths and slower gravity drainage under heterogeneity enhance the mixing between solvent and bitumen in the transverse direction along the edge of a steam chamber. Then, a larger amount of the accumulated solvent tends to facilitate lower temperatures near the chamber edge. Lower chamber-edge temperatures combined with restricted access to the overburden under heterogeneity alter the chamber geometry such that the contact area for overburden heat losses is further reduced.
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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 | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".