Development of Collapse Ratings for High Temperature and Pressure Coiled Tubing Applications
Bibliographic record
Abstract
Abstract In the spring of 1998, BJ Sevices and Total Oil Marine carried out an "HP Intervention Feasibility Study" for the reliable entry of a high pressure gas well using 1 ¾" 100 ksi Coiled Tubing. The research was prompted by the requirement to use Coiled Tubing to enter Triassic wells on the Alwyn North platform in the North Sea for post frac cleanout operations among other service requirements. Potential wellhead pressures of 7,500 psi and operating depths of 6,000 metres meant that a better understanding of Coiled Tubing collapse mechanisms and an improved method of predicting collapse would be vital to optimize operations on Triassic wells. The first phase of this study was based on experimental fitness-for-purpose investigations involving a 3060 ft long test string at an on-shore test well in Aberdeen, Scotland. Recognising the conservatism of collapse resistance predicted by existing theoretical methods and appreciating that knowledge of actual collapse limits is more critical in High Temperature and High Pressure (HPHT) coiled tubing operations, this initiative culminated in a joint research venture between the operator and the coiled tubing service provider. The second phase of this research involved a laboratory collapse-testing program conducted in Edmonton, Alberta, that set out to obtain extensive experimental data on CT collapse and to investigate the effect of loading history on the residual collapse strength. This paper is concerned primarily with the laboratory-testing program. The testing protocol is described and the key parameters that influence collapse resistance are identified and discussed, as well as how each may be affected by plastic cycling, high temperature and/or high pressure operations. Some selected experimental results are presented. Although actual factors of safety against collapse requires knowledge of the individual test results, general trends for the degradation of collapse resistance due to prior service loading and the range in magnitude of the difference between actual and predicted collapse strength, are identified. Theoretical predictions of collapse resistance are based on existing formulations in which the ovality and axial loading appear as explicit parameters. Collapse predictions are also discussed in light of a newly proposed methodology submitted to the API under RP 5C7 as recommended practise for determining allowable collapse pressures on coiled tubing. A new methodology for accurate prediction of CT collapse that is based on measured stress-strain plots, is 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 | 0.003 | 0.012 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".