NDLI: Wellhead Fatigue Analysis Method

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Reina˚s, Lorents Ho̸rte, Torfinn Sæther, Morten Gryto̸yr, Guttorm
Copyright Year	2011
Abstract	Re-completion and re-drilling of existing wells and introduction of new large drilling rig systems are elements that have led to renewed focus on the fatigue capacity for existing and new subsea wells. Due to lack of applicable codes and standards for such fatigue calculations, a unified analysis methodology has been developed and described in a Wellhead Fatigue Analysis Method Statement (MS). The intention of this work is to reflect the best practice in the industry and to provide an important contribution to well integrity management. The analysis methodology is limited to fatigue damage from dynamic riser loads present during subsea drilling and work over operations. The analysis procedure may be divided into three parts. i) A local response analysis that includes a detailed finite element model from wellhead datum and below. Interaction between the structural well components and soil structure interaction is properly accounted for. The main result from this analysis is the load-to-stress curve that describes the relationship between the riser loads at the wellhead datum and the stress at the fatigue hot spots. The analysis also provides the lower boundary conditions of the global load analysis model. ii) A global load analysis where the floating mobile drilling unit (MODU) motions and wave loads on the riser are taken into account. The results are time series or load histograms of the loads at wellhead datum, with focus on the bending moment, in all relevant environmental sea states. iii) Fatigue damage assessment, where a mapping of the loads with the relevant load to stress curve is carried out together with subsequent fatigue damage calculation. Appropriate S-N curve is applied together with wave scatter diagrams for the relevant operations and durations. The final result is the accumulated fatigue damage. With a unified analysis methodology in place particular attention is placed on a structured and specified analysis input and output. Results are suggested presented as a function of time and also as a function of key analysis input parameters that are associated with uncertainty. These are prerequisites from a well integrity management perspective in ensuring analysis results that are comparable. This paper presents the essence of the Wellhead Fatigue Analysis Method that was developed in cooperation between Statoil and DNV. Currently this analysis methodology is under extension and revision in the joint industry project (JIP) “Structural Well Integrity During Well Operations”. 11 operators participate in this JIP which also has structured cooperation with equipment suppliers, drilling companies and analysis houses. The aim is to form a wellhead analysis recommended practice document.
Sponsorship	Ocean, Offshore and Arctic Engineering Division
Starting Page	693
Ending Page	703
Page Count	11
File Format	PDF
ISBN	9780791844335
DOI	10.1115/OMAE2011-50026
Volume Number	Volume 1: Offshore Technology; Polar and Arctic Sciences and Technology
Conference Proceedings	ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering
Language	English
Publisher Date	2011-06-19
Publisher Place	Rotterdam, The Netherlands
Access Restriction	Subscribed
Subject Keyword	Drilling Uncertainty Seas Time series Fatigue Drilling rigs Mobile offshore drilling units Fatigue analysis Waves Stress Pipeline risers Finite element model Electromagnetic scattering Engineering standards Soil Ocean engineering Boundary-value problems Risers (casting) Wells Fatigue damage
Content Type	Text
Resource Type	Article

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Wellhead Fatigue, Effect of Uncertainty in Directional Variation and Environmental Conditions for Operations of Short Duration

A Simplified Methodology for Comparing Fatigue Loading on Subsea Wellheads

Analysis Approach for Estimating Wellhead Fatigue

Comprehensive Instrumentation of Two Offshore Rigs for Wellhead Fatigue Monitoring

Wellhead Monitoring: Measured Fatigue Damage Validation

Comparison of Real-Time Measured and Predicted Wellhead Fatigue Performance in a Deepwater Drilling Operation

Overcoming Installation Challenges to Wellhead and Conductor Fatigue

The Effects of Modelling Techniques and Data Uncertainty in Wellhead Fatigue Life Calculation

Uncertainty of Long Term Fatigue Load of Subsea Well Heads

Wellhead Fatigue Analysis Method

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