Stress Analysis of Perforated Casing in Shale Formation using Staged Finite Element Method
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Bibliographic record
Abstract
At present, collapse of perforated casing of some wells in shale formation during high-pressure fluid injection of massive hydraulic fracturing has been commonly observed. In order to accurately predict the stress state of the perforated casing during shale fracturing and identify the key factor affecting the perforated casing stress, a finite-element-method (FEM) mechanical model of perforated casing in anisotropic formation was established through staged finite element method (FEM). With this model, this study analysed the mechanism underlying the effects of injection fluid temperature, internal casing pressure, and cement properties on the stress of the perforated casing. Results show that thermal loading significantly affects the stress of perforated casing. The wellbore temperature decreases by 80 C, and the stress of perforated casing increases by 11.9 % correspondingly. The reduction in internal casing pressure and appropriate increase in cement stiffness can greatly reduce the perforated casing stress. The appropriate Young's modulus of the cement for field operations ranges from 30 GPa to 45 GPa. Variations in in-situ stress and pore pressure slightly influence the stress of perforated casing. Moreover, the stress of perforated casing decreases with increasing Young's modulus of formation. The stress of perforated casing reduces by 24 % when the anisotropy index reaches 1.2. The findings of this study can be used for the risk evaluation of the perforated casing failure during hydraulic fracturing, and also provide theoretical guidance for parameter optimization of field practices in cementing and hydraulic fracturing.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| 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 it