Non-Linearity and Stress-Dependency In Unconsolidated Formations and the Associated Impacts on Thermal Recovery: An Analytical Assessment
Bibliographic record
Abstract
Abstract In thermal recovery from unconsolidated oilsands reservoirs and in association with fluid mobility, formation compressibility and modulus of elasticity are closely related to pressure transient and stress redistribution behavior, which can collectively affect the steam chamber development. The non-linearity and stress-dependency in bulk compressibility and modulus of elasticity of rocks has been captured through the development of elegant constitutive models (e.g. nonlinear elastic hyperbolic model) and has been readily integrated into coupled reservoir-geomechanical simulation packages. To assess the significance of these nonlinearities for reservoirs with different initial stress states, this paper presents an analytical study where the associated impacts on the redistribution of stress (stress-paths) and the onset of geomechanical mobilization (shear dilation) under the assumption of uniaxial deformation are quantified. Within the scope of this paper, (semi-) analytical modeling is conducted while special attention has been devoted to (1) the vast range of depths of the existing oilsands reservoirs and the associated implications on the initial stress distribution as well as stress redistribution due to steam/water injection, (2) the impacts on the onset of geomechanical mobilization within the practical ranges of injection pressures, and (3) the evaluation of geomechanical mobilization potential for thermal (steam injection) versus non-thermal (cold water injection) pressurization. The results show that (1) the potential impact of stress dependency on the variability of the geomechanical properties (modulus of elasticity, Poisson's ratio and formation compressibility) is more significant for shallow reservoirs as compared to mid-depth and deep reservoirs, (2) the injection pressure required to onset the geomechanical mobilization may be under/overestimated if the non-linearity in the mechanical properties is overlooked, and (3) the thermal geomechanical mobilization (steam injection) may have a higher potential within practical ranges of operating pressures as compared to non-thermal techniques (cold water injection), especially for shallower reservoirs. The inherent limitations of the analytical workflows as well as the requirements of supporting efforts through coupled reservoir-geomechanical simulations are also discussed.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".