Session: 04-05-02 Subsea Structures & Equipment II

Submission Number: 182280

Spectral Distribution of Analysis and Measurements for Reliable Predictions of Subsea Wellhead Loads 

Subsea wells shall be designed to maintain structural integrity with respect to both fatigue and extreme loads. Operations on the well performed by a floating drilling unit during construction, completion, intervention and abandonment impose significant dynamic bending moments and shear forces to the well. The magnitude of the dynamic loading is determined by a combination of rig design, riser design, environmental conditions and the support provided by the soil surrounding the well structure. To ensure that neither the structural- or fatigue capacity of the well is exceeded, site specific simulations modeling the drilling operations are usually performed prior to the operations. To further enhance confidence during the drilling operations, dynamic loading and well integrity can be monitored through sensors installed on the riser and BOP. Having accurate predictions of the loading of the well will lead to more efficient planning process of the operations and can reduce costs related to unnecessary conservatism in the well design. Environmental conditions, hydrodynamic loading on complex structures, soil support all impose inherent uncertainties to the simulation models. In addition, rig motions, riser motions, and BOP motions will be dependent on a complex interaction of resonance periods. To enable prediction improvements with general applicability, identification of strengths and weaknesses of the simulation models should come from an investigation of as many operations as possible. By comparing results from up-front simulations and measurement data obtained during the real-life operations spanning a significant variety of vessels, environmental conditions, riser- and well designs will provide insights into how well the simulation models predict the dynamic loads acting on the well during drilling and completion operations. This paper proposes a method of comparing the overall magnitude and the spectral distribution of the dynamic loads acting on the well from both upfront analysis and measurements. General trends from a dataset containing drilling operations on more than 50 wells, performed in the North Sea, Norwegian sea and the Barents Sea are discussed with respect to frequency content, resonance behavior and total fatigue loads.

Presenting Author: Thomas Arnulf 4Subsea

Presenting Author Biography: 10+ Years of experience in global and local wellhead load analysis, and processing of measurement data. Product owner of Conductor analysis in 4subsea.

Authors:

Thomas Arnulf 4Subsea
Harald Holden 4Subsea