Follow-up of incidents has shown that mobile facilities have in some cases waited too long to move to their safety condition (survival draught). The PSA investigated two such incidents in 2020. On 3 March 2020, the West Mira mobile rig lost position while drilling. This caused the lower marine riser package (LMRP) to disconnect automatically and the rig moved off the well.
Read more: Seadrill – West Mira – investigation of unintentional disconnection of LMRP
A similar incident with West Hercules in 2019 was also investigated by the PSA.
Read more: Seadrill – West Hercules – investigation of unintentional disconnection of LMRP
On 29 February 2020, the gangway between the Floatel Endurance accommodation facility was automatically disconnected from the Martin Linge fixed platform because of wave loads.
None of these incidents caused personal injuries or major discharges/emissions, but could have done so in different circumstances.
Supervision
Following the West Mira investigation, Seadrill was ordered to identify and initiate measures which ensured that similar incidents did not recur on West Mira or the company’s other facilities. Meetings were held with both Seadrill and Floatel International on measures adopted after the PSA’s investigations. To contribute to improvements in companies with mobile facilities, the PSA carried out a number of audits on the subject of stability and marine systems in 2020-21. The Norwegian Maritime Authority (NMA) participated in several of these.
Similar audits are planned in 2022, but with greater emphasis on learning from earlier audits. In some cases, the PSA has also addressed the operator companies chartering the mobile facilities. They have a special responsibility for their operation, and determine such matters as the criteria for disconnecting facilities in the event of gales, for example.
Information and guidance
The PSA staged a webinar in January 2021 on weather criteria for drilling operations on mobile facilities. Together with the NMA and classification society DNV GL, the PSA used this occasion to clarify the requirements which applied under different weather conditions. Several companies also shared their experience. Some 500 people followed the webinar. The invitation noted that challenges exist in defining and applying the boundaries between normal operation and weather-dependent conditions which require a halt to operations and a concentration on maritime securing of facility and crew (known as the safety condition or survival draught). With the webinar, the PSA wanted to work for more secure operation of mobile drilling facilities in conditions where the weather imposes operational restrictions.
The PSA also held a meeting with a restricted number of participants to follow up an incident where waves hitting the bottom of a deck box caused damage and loosened a lifeboat. Loss of position was also a topic at a webinar on structural safety on 1 September 2021.
In addition, the PSA has presented RNNP results related to structural safety, and loss of position in particular, both to the Safety Forum and in a separate meeting with the Norwegian Shipowners Association. On behalf of the PSA, Sintef conducted a study of wave loads which can cause loss of position for DP-operated facilities. Published in October 2021, this found that the effect of wave drift forces should be taken into account when establishing operating criteria.
Effects
The responsible companies have taken extensive measures as a result of the PSA’s investigation and audit reports. These are all published on its website, and the investigation reports in particular attract much attention both from other companies and in sector fora. It is therefore reasonable to assume that the reports have led to necessary measures also being adopted in other parts of the industry.
Part of the purpose of the audits was to discuss technical issues in such a way that the companies acquired new learning. They also had an element of guidance. The PSA sought to help the companies with mobile facilities take more of an independent responsibility in an area where a classification society or consultancy has traditionally played an important role.
At industry level, the PSA has conducted a study which provides new knowledge about operational criteria. Through webinars, meetings and other communication, it has helped to make more players aware of the challenges, the requirements which apply for safe operation, and the newest knowledge in the area. In its view, experience-sharing by both government and companies will both increase the motivation of the audience and provide access to new solutions which can contribute to change.
Data from the RNNP show a decline in incidents related to positioning and the positioning system from 2020 to 2021. The two cases recorded were both on vessels, and neither related to weather criteria. The figure is too low to be able say anything certain about causes, but the PSA assumes that the increased attention being paid to this subject by it and the industry will contribute to improvements.
This article is taken from the PSA’s annual report for 2021 to the Ministry of Labour and Social Inclusion. Access the whole report here (in Norwegian only, English summary).