Location: North Sea

Product: Riser and Conductor Analysis

Background

Aquaterra Energy provided detailed riser and conductor analysis for an exploration well off the Norwegian coast. The client, a major oil and gas company, initially approached us with a very short timeline of 8 weeks before drilling was due to start, seeking urgent third-party verification. The client had previously received a fatigue life assessment of only 3 days for their riser system and associated equipment, which would make their equipment insufficient for their planned 82-day drilling operation, and thus cause serious delays and substantial added costs.

The client’s exploration well featured a wellhead with a load ring design, which added an element of complexity to the analysis. Our in-house team of offshore analysts has significant experience modelling these types of wellheads and was able to provide accurate assessments to this type of well.

Given the client’s tight timeline, with plans to drill in early January, there was significant urgency to complete the analysis and provide recommendations as quickly as possible.

Solution

Our in-house team utilised a combination of software, including Aquaterra Energy’s in-house specialist analysis software Orange and Orcaflex. We built detailed models including appropriate simulation of the complex wellhead behavior, running comprehensive fatigue, structural, and vortex-induced vibration assessments. Orange proved crucial in this project for its ability to quickly and effectively build the needed base models and extracting key data/results from thousands of loadcases.

We maintained close communication with the client, providing regular updates and results via email and weekly meetings. Our team worked closely with the client to discuss possible areas of conservatism within the analysis, such as utilisation of cathodic protection and connector protection from sea water ingress. This close communication and collaboration made the results both more accurate and less onerous.

Rather than simply identifying issues, we proactively developed solutions to improve the fatigue life. For example, we identified an area of high cyclic stress spanning less than the length of the conductor joints used and collaborated with the client on shifting the connectors out of high-stress zones, resulting in a significant increase in the predicted fatigue life.

Factored wave fatigue damage, highlighting the original connector elevations for a more accurate representation of the system

Results:

Our detailed analysis was completed in approximately 20 days from when the client contacted us, a remarkable turnaround given the complexity of the project and the client’s tight timeline. The final results showed a fatigue life of 132 days, well exceeding the client’s 82-day operational requirement and the initial 3-day estimate.

The client was highly appreciative of our approach, particularly the open communication, timely updates, and the team’s ability to provide solutions rather than just identifying problems. The client noted that our teams work effectively “saved Christmas,” as it allowed the project to proceed as planned in the new year, avoiding potential delays or cancellation and avoiding the clients team to have to work overtime during the holiday period.

As the rig was already contracted for the operation, cancelling the project could have resulted in a multi-million pound loss. Our analysis allowed the client to proceed with the planned drilling operation with confidence and a workable solution.