North Sea Approach to Platform Decommissioning

Wed, 01/25/2012 - 11:56

While the decommissioning of platforms and the dismantling of drilling rigs is primarily an emergency response measure in the Mexican oil and gas industry today, the topic is destined to gain prominence in life- cycle planning as Mexico’s offshore fields mature. The decommissioning process requires the evaluation of all options for the physical removal and disposal of offshore infrastructure at the end of its working life, and the evolving set of international best practices provides a context for the upcoming decommissioning decision-making process at Pemex.

The North Sea, where the first platforms were installed in 1968, has experienced a significant rise in the decommissioning of platforms in recent years. The OSPAR (Oslo-Paris) Convention establishes that all platforms have to be removed at the end of their lifetime. All topsides and steel jackets weighing less than 10,000 tonnes must be returned to shore for re-use, recycling or final onshore disposal, and jacket piles have to be severed below the seabed at a depth that prevents them from being exposed. Under this scheme, over 470 platforms will need to be wholly or partially removed in the next 30 years at a cost in excess of US$73 billion, according to the North Sea Offshore Decommissioning Report by Douglas-Westwood and Deloitte Petroleum Services Group.

The Brent Field, which has given its name to the North Sea’s major trading classification Brent Crude, that comprises a mix of the sweet light crudes Brent Blend, Forties Blend, Oseberg and Ekofisk, played a central role in the development of decommissioning in the North Sea. Discovered in 1971 on the UK Continental Shelf, the Brent Field began oil production in 1975 and became a predominantly gas field in the mid-1990s following the largest and most comprehensive field redevelopment undertaken in the North Sea to date. Part of the field’s redevelopment involved the decommissioning of the Brent Spar, which was scheduled for deepwater disposal in the deep Northern Atlantic, a Best Practicable Environmental Option approved by the UK Government. In early 1995, Greenpeace activists occupied the Brent Spar claiming it to be a toxic time bomb, and arguing that disposing of the Brent Spar in the deep Northern Atlantic, or possibly the North Sea, would set a precedent for the potential dumping of 400 oil rigs in the North Sea over the following decades. Following large scale public protest in continental Europe, and resulting political pressure, Shell Exploration presented the ‘Our Way Forward’ programme at the end of 1995, inviting major contractors to develop the best solution for spar disposal or re-use. According to Shell’s Brent Spar Dossier, the Brent Spar project was effectively completed on July 10th 1999 when cut and cleaned ring sections of the buoy’s hull were placed on the seabed at Mekjarvik, near Stavanger in Norway, to form the base of a new quay. Ultimately, the Brent Spar decommissioning underscored the importance of taking input from all stakeholders into consideration, and establishing a playing field for decommissioning in the North Sea that safeguards public safety and health and minimizes environmental impact.

Heerema Marine Contractors not only participated in the decommissioning of the Brent Spar, but also completed the North West Hutton removal for BP and decommissioned and removed the nine remaining platforms at ConocoPhillips’ Ekofisk field in Norway. “In the North Sea, we are probably one of the market leaders with respect to decommissioning and removal,” says Erwin Lammertink, Vice President Commercial and Business Development for Mexico, Europe and Russia at Heerema Marine Contractors. His company provides tailor-made solutions for deepwater field development, heavy lift, float-over, decommissioning and removal, which is becoming an ever-growing part of Heerema’s operations. “The decommissioning and removal business is something totally new and one might think that it’s the reverse of installing a platform. However, the fact that a structure has been standing in a hostile offshore environment for 20 to 30 years, being susceptible to corrosion, fatigue, storms, and contact with vessels, equipment and hazardous materials, could mean that not all of the structural data is still available or accurate. This makes the removal of platforms quite a challenging task in terms of engineering and execution with our vessels as well as from a safety and environmental point of view,” says Lammertink. “It is also very important to find the right contracting model for these projects. How do you define risks when removing infrastructure that has been in an offshore environment for 30 years, and how do you share these risks between the client and the contractor? We have learned this by doing and are therefore able to cooperate with our clients to minimize risk and improve our contracting model every time.”

Incorporating such international best practices will enable Pemex to optimize safety, health, environment, and economic performance as production decline in Cantarell and Ku-Maloob-Zaap triggers the commencement of the decommissioning in Mexican waters. “In the North Sea, we are one of the market leaders with respect to the cessation and removal of platforms, but we haven’t seen or been confronted with dedicated cessation or removal projects within Pemex, yet,” says Lammertink.