The Effect of Heterogeneity on In-Situ Combustion: Propagation of Combustion Fronts in Layered Porous Media
Bibliographic record
Abstract
Summary In-situ combustion is a potential method for the recovery of heavy oil. The effect of reservoir heterogeneity, a ubiquitous feature of oil reservoirs, on in-situ combustion has not been systematically addressed in prior studies, however. In this paper, we present analytical models for filtration combustion, namely the combustion of a stationary solid fuel, in the specific case where the reservoir consists of two layers of different permeability and thickness, separated by nearly impermeable shales. We investigate the conditions for the propagation of steady combustion fronts as a function of some key parameters, including the permeability-thickness contrast R between the layers, the thickness ratio η, and the external heat loss coefficient h. We find that heterogeneity acts in two distinct ways: It reduces the temperature of the leading front in the high-permeability layer in all cases, and uncouples the propagation of the fronts in the two layers if R is smaller than a critical value Rc. The first effect may lead to low-temperature oxidation conditions, and therefore to the effective extinction of the front in the high-permeability layer. The second leads to a reduced sweep efficiency (and early breakthrough). However, if R exceeds the critical value, the fronts in the two layers travel coherently (with the same speed). This coherence is identified for the first time. The resulting thermal coupling greatly retards the front in the more permeable layer, and accelerates only slightly that in the less permeable one, until the two fronts reach a common velocity. We study the effects of R, the heat loss rate, and the ratio of thickness η. The coupling is aided by moderate heat losses (small h), and smaller η, which affect the critical value Rc.Asinthe homogeneous case, at sufficiently high heat loss rates, steady front propagation cannot be sustained and the combustion process becomes extinct. The work is useful for the understanding of the viability of in-situ combustion process in heterogeneous layered reservoirs and the effect of a number of injection, combustion, and reservoir parameters.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 teacher head, 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".