Effect of External Mechanical Damage on the Fatigue Life of Coiled Tubing Exposed to Sour Environments
Bibliographic record
Abstract
Abstract In normal operations, coiled tubing (CT) is frequently subjected to mechanical damage on its outer surface that could adversely affect its fatigue life. The effect of transverse external mechanical damage, with depths in the range of 10% to 20% of the nominal wall thickness, on the fatigue life of grades 90 and 110 CT samples exposed to sour environments (i.e. solution NACE A saturated with 100% H2S) was reported in a previous paper (SPE 107113). The results showed that the fatigue life of the pipe was reduced significantly when the samples were pre-exposed to the sour environment used for these experiments. Additional testing was subsequently performed to asses less severe damage depths (i.e. < 10%) and orientations (i.e. longitudinal), less severe environmental conditions (i.e. H2S concentrations lower than 100%), application of anti-cracking inhibitors, and the response of other CT grades (example: grade 100). The present paper summarizes the results from the fatigue testing of more than 100 CT samples (grades 90, 100 and 110) with artificial mechanical damage in the transverse and longitudinal orientations, and depths from 5% to 20% of the nominal wall thickness, after being exposed to different sour environments (H2S concentrations from 1% to 100%) and including three different anti-cracking inhibitors. A comparison between the sour fatigue life of the samples containing external mechanical damage and that of samples without damage is presented in terms of percentages of sweet life (i.e. fatigue life measured in air). Also, the effects of the damage depth and orientation, H2S concentration, and anti-cracking inhibitors on the fatigue life are analyzed. Finally, an inspection criterion for mechanical damage on strings to be used in sour environments is proposed.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".