Decommissioning Technology Challenges
Authors: Prasthofer Peter H. 
Published: October 2008

Abstract
The E&P industry faces a major challenge over the next 25 years in being able to decommission over 6000 platforms worldwide in an optimal manner which seeks to find the right balance among health/safety, environmental, technological, and economic considerations. This balance needs to be achieved within the confines of a tight regulatory framework, while also being mindful of public attitudes and concerns. This paper will address the key technological and operational challenges in decommissioning, in particular those related to the removal and disposal of large steel and concrete platforms, followed by a brief discussion of socio-economic considerations. The results of a series of studies undertaken by the Offshore Decommissioning Communications Project (ODCP) will be included. Finally, the broader issue of communicating and discussing complex technical issues and decision processes with the public at large will also be touched on.

Introduction and Scope of the Problem
The international oil and gas exploration and production industry and the offshore contractor community face a formidable challenge over the next 25 years to decommission some 6000 platforms worldwide (Ref. 1). These platforms range from small single well structures in the Gulf of Mexico to heavy deepwater structures in the North Sea and offshore California. The platforms are located in some 53 countries around the world with varying degrees of supporting infrastructure and .wide ranging climatic conditions (Fig. 1). In performing this task industry will not only need to overcome the formidable technological and operational challenges, but will need to ensure that the right balance is achieved among health/safety, environmental, technological, and economic considerations. This has to be achieved within the requirements of a tight regulatory regime, while being mindful of public attitudes and concerns. The cost of removing and disposing of these 6000 platforms has been estimated to range between 20 to 40 billion US dollars. While the North Sea area only includes about 7 percent of the total number of platforms, these account for about 60 percent of the worldwide decommissioning costs. This is due to the weight and complexity of those installations, as well as the severe weather conditions making removal and disposal operations time consuming and difficult. While some 1500 platforms have been removed to date in the Gulf of Mexico alone (Ref. 2), only 27 have been removed in the North Sea and there is almost no experience with the removal of large heavy platforms. This lack of experience not only adds to the technological challenge but also accounts for the wide band in the cost estimates. The technical and operational challenges deal not only with removal, but also with disposal (what to do with the parts of the installation after they have been removed). Evolving regulatory philosophy changes being embodied in revised international and regional conventions and increased public focus on environmental issues as demonstrated in the Brent Spar affair, has put greater emphasis on disposal issues such as recycling versus sea disposal and the environmental consequences of such decisions. Environmental consequences has taken on a broader meaning than just the direct impact and includes such considerations as resource conservation and energy use during decommissioning operations. In this context it is important that technical studies address not only those issues deemed critical by the practitioners, but also Issues and concerns raised by other stakeholders. Major issues of current concern and the results of studies undertaken to address those issues will be discussed in later sections. Some of the difficulties in devising an