Casing Ultradeep, Ultralong Salt Sections in Deep Water: A Case Study for Failure Diagnosis and Risk Mitigation in Record-Depth Well
Why this work is in the frame
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Bibliographic record
Abstract
Abstract The deepest well drilled to date in the Gulf of Mexico, the Well #1 discovery well in Green Canyon, required setting casing in a 15,000 ft thick section of tectonically active salt. After casing collapsed in the initial wellbore, a comprehensive model was developed to characterize wellbore stability, salt creep mechanism and implications for well design, and mitigation options for future well construction. To facilitate the construction of models characterizing the interaction of casing and salt, the regional pore pressure and in-situ stress setting was analyzed. This analysis revealed that pore pressure in this area shows a significant regression in the subsalt formations. This pore pressure regression, if not accurately predicted, can lead to significant problems with the wellbore including wellbore breakouts and drilling fluid losses. The combined challenges of open-hole wellbore instability, salt creep, and casing damage made well design and construction very difficult. In this paper, models are utilized to replicate wellbore instability, salt creep and the interaction of halokinesis, wellbore geometry, casing stress, and drilling fluid hydrodynamics. The modeling reveals that casing failure was caused primarily by non-uniform contact of salt on casing thereby generating stresses that exceeded the yield strength of the lightweight casing. The same model showed that heavier casing could withstand identical, non-uniform stresses if loading was diametric and not axial. The model was used to prepare an optimized drilling program that mitigates the risk of non-uniform application of stresses by salt and non-uniform application of slip loading. Recommendations included under-reaming in the slip zone, the use of drilling fluid of appropriate composition, and cementing practices that improve the stress distribution on the casing. Further, after setting casing through the salt, relatively high mud weights were required to avoid a large differential between internal and external loading on the casing. High mud weight had implications for wellbore stability in open-hole while drilling the subsalt sections to reach the reservoir. Modeling predicted accurate in-situ stresses and pore pressures that were utilized to drill a bypass well that successfully reached an unprecedented depth of 34,189 ft. Both analytical and 3-D elasto-plastic finite element methods (FEM) were applied to analyze casing failure mechanisms, coupling the effects of in-situ stresses and mud pressures with the overburden. The methods were also applied to analyze mineralogic parameters that influence salt creep. The modeling process is applicable to essentially all Gulf of Mexico extended-reach wells to be drilled through salt sections.
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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 | 0.000 | 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 it