Calculating wellhead fatigue

Paul Boughton

Fugro has completed a year-long wellhead monitoring project for BP Americas Inc, measuring blowout preventer (BOP) stack motions and calculating wellhead fatigue during a deployment in the Gulf of Mexico.

The drilling campaign was conducted throughout 2014 in 6,000ft of water depth and utilised the Fugro Wellhead and Riser Instrumentation Service (WARIS). This installation included transmission of motion spectra from the BOP stack and riser using standard hydroacoustic modems and the automatic processing of this data with topside environmental data to show levels of motion and fatigue and their correlation with sea states and ocean currents. This provided BP with access to real-time subsea data to aid their decision making throughout the deployment.

Communications from the lower marine riser package (LMRP) and riser remained successful even with surface wave heights greater than 3 metres at times during the campaign.

The DeepData subsea motion monitoring pods, the main component in the system, were deployed to positions on the BOP stack and riser by a remotely operated vehicle (ROV). The pods were integrated with hydroacoustic modems and had battery capacity to last for one year of deployment. A topside system was supplied that included vessel motion monitoring and links to existing environmental monitoring systems.

To ensure that the data could be accessed and utilised by BP engineers anywhere in the world, Fugro’s onshore data delivery system was used to plot and display all the processed data from the WARIS system. Summary plots were also distributed by email to a designated list of client recipients.

The success of the project indicated the technology could be deployed on other wells where fatigue capacity and potential loading is of interest.

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