Abandonment of obsolete wells and installations one the Norwegian continental shelf. A study into the magnitude of the technical and economic challenges.

Abstract

An increasing number of offshore installations on the Norwegian continental shelf (NSC) are passed their peak production, they require more and more maintenance and/or investments, and are rapidly approaching their end of economic life. The final stage in an installations life is Cessation. This is a time-consuming, complicated and costly activity, but it is necessary in order to protect the environment and fulfill mandatory national regulatory requirements as well as international regulation. This paper addresses the technical and economic challenges related to Cessation activities on the NCS. Regulatory requirements both related plugging and abandoning wells and decommissioning installations, are covered. Plugging and abandonment of wells is described in detail, existing techniques and technologies as well as unconventional methods. This part of the paper also discusses the magnitude of P&A on the NCS, i.e. the number wells already drilled and expected in the future and the amount of work required to plug them in a safe and prudent manner. Decommissioning of offshore installations, including disposal, is covered in a separate chapter, describing methods, their challenges and shortfalls, as well as the anticipated amount of work needed to be done in the future. The economics of Cessation is covered in detail, together with some deliberations around the net present value (NPV) and cost-benefit of the substantial expected costs. In addition to the outlooks for the future, a specific example of a concrete case regarding Cessation of an installation in the southern part of the North Sea is covered. The last part of the paper is a discussion around the changes that are required in order to approach the many challenges associated with Cessation in a cost effective manner, benefiting both the industry and the Norwegian society.