Permanent Plugging and Abandonment - An identification and discussion of technologies and the differences in UKCS and NCS regulations

Abstract

There is a large number of wells on the Norwegian Continental Shelf that need to be permanently plugged and abandoned (P&A) within the next decades. As P&A does not provide any income, it is very important to develop cost-effective methods to perform the operations. This thesis gives a brief presentation of how plug and abandonment operations are performed and which challenges that exist within the field. Further some selected technologies which are under development or recently implemented in the industry are presented and discussed. In addition to the technological challenges, it is also likely that the regulations can play a role in achieving more effective solutions. The main objective of this thesis has been to analyse the Norwegian standard that is valid for P&A operations and compare it to both the existing guidelines on the UK continental shelf and to a risk-based perspective proposed by DNV GL. The UK industry is more experienced than the Norwegian and operate in similar waters, therefor it makes sense to compare the two to find ways of improving NORSOK D-010. The risk-based perspective provides a new approach to P&A which is in line with the overall trends of the industry where risk-based decision making is becoming increasingly emphasised. The comparison of these three documents resulted in several suggestions for improving the NORSOK D-010, and for additional guidelines that might be useful on the NCS. Another aspect of this thesis has been to investigate how new technologies can be used to improve P&A activities as this is likely to be the main contributor for more cost-efficient operations. The overall goal of the technologies presented is to eliminate the need for a rig as this is one of the highest costs in P&A. Also, rigs are better used for drilling where there exists potential revenue for the operators. Some of the technologies have been implemented whereas others struggle to achieve qualification and be tested. The industry is conservative and there is a certain reluctance towards trying new technologies, when there are already solutions that works implemented. This thesis suggest that part of the problem lies within the phrasing and requirements found in NORSOK D-010 which appears to be very strict. The result of this thesis is a list of recommendations on how to improve the NORSOK D-010 to close the gap between UKCS and NCS regulations. It further provides recommendations for how to better open for alternative technologies and methods to be implemented in P&A operations.