The recovery and readiness of the drill ship’s mooring system as well as further work in preparation for its future activities, is expected to provide local contractors with a significant work programme over the coming months.
The ship had been drilling the Ruru exploration well off the South Taranaki coast for operator Shell Todd Oil Services (STOS) when a severe storm struck on 26 April and some of the anchor lines failed. The vessel was then released from the remainder of the anchor lines and steered to safety away from the Ruru well, to deeper waters and well beyond both the Maui Platforms and the Tui FPSO.
The safety systems and processes worked as they were designed/intended to and there was no harm done, no harm to those on board, the environment or the Ruru well. A comprehensive assessment of the vessel revealed there was only minor damage to the vessel itself and this has been repaired relatively quickly.
The main focus over the coming period will be for the vessel owner to develop plans with input from STOS to recover the Riser and the Lower Marine Riser Package (LMRP) from the seabed. This work may be assisted by the Noble Discoverer from Port Taranaki. One option involves disconnecting the LMRP from the riser and another option is to salvage the complete riser system on location. These plans are being finalised.
Keeping the Noble Discoverer at Port Taranaki is recognition and a real bonus for local engineering contractors with the planned work programme potentially providing local businesses with contracts worth many millions of dollars.
Meanwhile, investigations continue into why some of the eight anchor lines holding the vessel failed during the storm. The remaining lines were disconnected and it was moved into deeper waters to ride out the storm. This was a mechanical issue and in no way compromised the safety and integrity of the well that was being drilled, the vessel or the rig personnel.
As a precautionary measure and in accordance with best industry practice the crew disconnected the vessel from the well-head before the storm hit and closed in the well. This process involved:
- “hanging off” and disconnecting from the drill string
- closing and then locking the Blow Out Preventer rams in place
- disconnecting the riser and moving the vessel some 25 metres away from the wellhead
A seabed survey carried out by a Remotely Operated Vessel (ROV) soon after the incident showed no environmental impact, with both the wellhead and associated Blow Out Preventer (BOP) intact. The survey showed the BOP was locked in the correct position, with all the necessary nuts, bolts, flanges secure. It also showed the Riser and LMRP located some 80 metres away from the wellhead, on the seabed.
Discussions with regulators and community stakeholders are ongoing.
As safety is the first and foremost priority and with winter substantially reducing the opportunity to carry out safe operations, the vessel may not return to the Ruru well for some time.
Rob Jager General Manager, Shell Todd Oil Services Limited.
The Noble Discoverer is a fit-for-purpose drilling rig with a long history of safe, reliable offshore operations. The safety systems put in place worked as they were intended to during Taranaki’s adverse weather conditions last month, with no harm to people, the environment or the Ruru well.
The Noble Discoverer drillship was substantially upgraded and refurbished in 2001 and again in 2006. There was significant investment, including strengthening of the hull. In 2009, there was a $25 million retro-fit of the Discoverer’s generator exhaust system to comply with emissions standards. The Noble Discoverer was identified as the most appropriate and preferred rig option for Ruru before June 2010.
At that time there was considerable uncertainty for rig activities in USA as a result of the moratorium on drilling. This resulted in the opportunity for the Ruru venture to use the Discoverer for drilling the Ruru well during the New Zealand summer period. The issue with the consents for Alaska occurred well after the decision was made to bring the Discoverer to New Zealand.
Noble Discoverer Specs:
- Refurbished in Singapore in 2006 and 2007
- A turret moored drillship
- Berths for up to 124 persons (as currently outfitted)
- Owned and operated by Noble Drilling
- Water Depth – up to 2000 feet (1100 feet with the current riser assembly)
- Speed – 7.5 Knots
- Length – 157 Meters
- Crew – 65 (remaining 60 berths are for 3rd party personnel)