Abstract
Use of full bore high pressure (HP) risers in ever more challenging locations and conditions has increased requirements to collect in-situ response data to confirm that the riser design is acceptable and confirm integrity. Due to the challenging combination of the 91m water depth and harsh environment at Huntington field in the North Sea, considerable analytical work was required to design and configure the proposed 24inch diameter HP drilling riser and well conductor system to allow successful and safe all year operations from the jackup rig. As well as careful strength and fatigue design of the upper and lower most HP riser joints, this potentially required modifications to the rig’s CTU deck to support the high loads expected. Typical conservatisms in analysis methodologies also needed to be removed to allow for a viable theoretical design. In-field measurements were therefore proposed to allow for verification and calibration of the analysis used as a basis for the design decisions and to ensure that the integrity of the riser was maintained during the 12 months of drilling and completion operations. The monitoring system developed to address this, the first type of its kind to be installed on a jackup rig, incorporated a range of accelerometer and strain sensors to record motion, load and fatigue responses of the riser and jackup system in real-time.
This paper describes the background to the monitoring system design, the components that make up the monitoring system and presents the comparisons between the collected data and analytical predictions that allowed the objectives of verifying the analysis and confirming integrity of the riser to be achieved. Recommendations are also given as to how the monitoring system can be improved for future use in similar applications.
