Technical Feasibility of Tubing Risers
Bibliographic record
Abstract
Abstract A tubing riser is a type of top tensioned production riser (TTR), which has only the production tubing running through the water column. As a result, the top tension required to support a tubing riser is much less than for a traditional casing riser. This means that for ultra-deepwater structures (>5000 ft), riser payload and hull costs can be significantly lowered. For deepwater Tension Leg Platforms (TLPs), where TTRs are supported directly by the deck, lower top tension normally translates into payload and buoyancy reductions. For deepwater Spars, where air cans support most TTRs, lower top tension normally translates into reductions in air can and hull sizes. During Phase 1 of the Magnolia Development Project (ConocoPhillips and Ocean Energy), a Tubing Riser Design study was carried out to determine the feasibility of using tubing riser for all TTRs on the Magnolia ETLP. The results showed that the tubing riser concept is technically feasible. However, there are a number of areas needing additional study to make the concept more robust. In this paper, the technical feasibility of tubing risers is examined from the aspects of strength and fatigue (analysis), VIV and galloping (analysis and model testing), riser interference and stroke (analysis). In addition, general arrangement, composition and configuration will be described. Introduction Traditional top-tensioned production risers (TTR) have either one or two layers of casing outside of the production tubing. The primary function of the casing(s) is to prevent leaks to the environment and maintain pressure integrity in case of an internal tubing leak. As the weight of the casing is much greater than that of the tubing, it normally requires a significant amount of top tension to support a single or dual cased riser. For deepwater TLPs, the top tensions of traditional TTRs are a large percentage of the total payload and it requires a significant amount of hull steel to support the TTRs. The tubing riser is a type of top tensioned riser, which has only the production tubing running through the water column. As there is no additional casing to support, the top tension required to support tubing riser is much less than for traditional casing riser. The result of using tubing riser on ultra-deepwater structures (>5000 ft) is a significant reduction in riser payload. The effective payload for TLPs would increase without increasing the displacement by using tubing risers. As a result, the amount of hull steel could be reduced without sacrificing production capacity. And, this would significantly reduce the cost of the hull. Using tubing risers would reduce the size of air cans, most commonly used to support TTRs on Spars. Reducing air can size would significantly reduce the size of the moon pool and would, therefore, reduce the size of the hull. Even for the tensioner-supported Spar TTRs, reducing TTR top tensions would significantly reduce hull costs. The same can be said about other floating production systems using dry trees and TTRs.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".