Stability analyses for deviated wellbores in unconsolidated cross-anisotropic formations
Bibliographic record
Abstract
Production of oil from shallow reservoirs typically involves drilling highly deviated wells through unconsolidated (or poorly lithified) rocks or clays. This paper describes numerical analyses of the deformations and stability of deviated wellbores within a K0-consolidated clay. The analyses consider planar deformations in the plane orthogonal to the wellbore using a quasi three-dimensional (3D) finite element model that represents coupled flow and deformations within the soil mass. Cross-anisotropic mechanical properties of the clay are described by a generalized effective stress model, MIT-E3, with parameters previously calibrated from laboratory thick-walled cylinder tests. The analyses compute the relationship between the drilling mud pressure and wellbore stability associated with either the onset of localized failure mechanisms or large plastic deformations around the cavity. The results show that short-term, undrained stability requires mud pressures in excess of the in situ formation pore pressures for more highly deviated wellbores at inclinations greater than 45°. The analyses examine the mechanisms for further destabilization, due to consolidation within the formation, and how they are affected by drainage conditions at the wellbore wall. The results provide qualitative information for the design and control of drilling operations for deviated wellbores in unconsolidated formations.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".