Core-scale modelling of cyclic creep deformation caused by cyclic CO2 injection and storage in unconventional reservoirs
Bibliographic record
Abstract
• Cyclic creep deformation leads to lower CO 2 storage and oil recovery. • Cyclic creep deformation cumulatively reduces porosity and permeability in early cycles. • Rock matrix becomes more cohesive and resistant to creep deformation with increasing cycles. • Fractures enhance dissolved CO 2 phase and rock matrix (pore) free CO 2 phase. • Flow and transport gradually shift from diffusion to convection with successive cycles, lowering CO 2 -EOR. Cyclic CO 2 injection, followed by soaking and production—commonly referred to as “Huff-n-Puff” (HnP)—can be used to enhance oil recovery, while mitigating greenhouse gas emissions, from unconventional reservoirs. The cyclic loading and unloading stresses associated with HnP induces cyclic creep deformation in the reservoir. This study aims to investigate the impact of cyclic creep deformation on CO 2 storage and enhanced oil recovery (EOR) under varying geomechanical conditions. Intact and fractured core plugs from the Canadian Montney Formation were subjected to single-phase gas flow (gas permeability) measurements under multiple cycles of loading and unloading stresses, with rock and flow properties (e.g., permeability, porosity) determined for each cycle. The experimental data informed hydromechanical models incorporating various deformation scenarios (rigid, elastic, weakly elastic, and cyclic creep) and coupled with multiphase, multicomponent flow and transport models. Results reveal that cyclic creep deformation diminishes CO 2 -EOR potential by reducing permeability and porosity with each successive cycle, with fractures exhibiting greater reductions compared to the matrix. Accumulated creep deformation results in slower pressure buildup during CO 2 injection and a slower depletion rate during oil production. Consequently, CO 2 storage is reduced by 18% and 30%, and oil recovery decreases by 5% and 20% in the matrix (pore) and fracture domains, respectively, relative to models without creep deformation. Additionally, free and dissolved CO 2 storage volumes increase with each cycle, with fractures enabling significantly higher dissolved CO 2 storage (21%) compared to matrix-only storage (6%). A progressive reduction in diffusive CO 2 flow across cycles further highlights a transition from diffusion-dominated to convection-dominated flow due to increased effective stress. This study is the first to incorporate cyclic creep deformation into HnP models, demonstrating its critical role in influencing CO 2 storage capacity and EOR performance. Ignoring cyclic creep deformation effects can lead to overestimation of CO 2 storage capacity and oil recovery, emphasising the importance of accounting for these effects in the design of optimal HnP schemes for oil recovery and sustainable carbon management strategies.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| 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".