Running Fairings for Deepwater Drilling in the Gulf of Mexico - A Cost-Benefit Approach to Deciding the Faired Length
Notice bibliographique
Résumé
Abstract The decision to run fairings on drilling risers is critical in terms of the additional cost to run fairings versus downtime cost from suspended operations due to current conditions causing excessive flex-joint angles. Making an informed decision, enhanced by actual predicted current conditions for a drilling program, is a valuable capability in planning to maximize drilling uptime and minimize downtime costs. This paper presents an innovative model which has been developed as a rational decision tool for determining the fairing requirements to mitigate predicted loop current events for proposed drilling programs in the Gulf of Mexico. Introduction The Fairing Optimization Model provides an innovative approach to fairing length requirements based on an evaluation of the cost and benefits of running fairings for a planned drilling program. The model has been applied to several rigs under contract to ChevronTexaco. It provides the operator with a systematic approach to decide on limiting loop current conditions beyond which VIV(Vortex Induced Vibrations) suppression fairings will be required for a range of water depths in the Gulf of Mexico and to decide on the optimum number of fairings to run for a series of proposed drill sites. This model combines a loop-current eddy environmental prediction tool with results from an extensive analytical database of riser response. For a proposed drill-site, this model estimates the probability that a loop current eddy will adversely affect a proposed drill-site in terms of its severity and duration. An example model was developed for water depths ranging between 2,000ft and 9,000ft. The model clearly demonstrated that for a given drilling scenario and environmental forecast there exists an optimum (zero or non-zero) length of fairings below which cost of downtime exceeds the cost of running fairings and above which the cost of running fairings exceeds that of likely downtime. Methodology. The flowchart showing the steps taken to achieve an optimized fairing solution is given in Figure 1. The main steps to achieve an optimized solution are as follows:Riser Response AnalysisEddy PredictionFaired Length Optimization Riser Response To obtain an accurate representation of the riser responses in the field, it is important to model the riser according to the drilling contractor's operating philosophy. This entails using the actual riser properties, tensions, buoyancy distribution and mud weights that the contractor would use for a given drilling program. Once this data is collected, a load case matrix can be set up to encompass various water depths, top tensions, mudweights, and even vessel offsets. This allows for an extensive database of riser response to be created to emulate most drilling scenarios. The inclusion of a tension that represents the operating strategy of the contractor and varied vessel offsets is imperative because these two parameters are the most common methods used to mitigate VIV aside from auxiliary devices. An increased tension will damp out VIV motions and moving the vessel downstream will improve the upper flex joint angle to a certain extent. However, moving the vessel too far downstream will adversely effect the lower flex joint angle.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».