Havtil has initiated this knowledge gathering to contribute to the sharing of experience and information around the use of creeping shale as a well barrier element for permanent plugging on the Norwegian shelf.
Havtil’s regulatory requirement for permanent plugging of wells is that wells are secured with qualified well barriers before they are abandoned in perpetuity. Havtil work actively with the industry to ensure that both the regulations and associated standards are updated to reflect current best practice and prevent leaks for the foreseeable future.
Creeping shale has been used as a well barrier element between casings and formations on the Norwegian shelf since 2006. The minimum requirements for the use of creeping shale and it’s function and performance requirements in permanent plugging and abandonment (PP&A) are described in NORSOK D-010 EAC 52.
NORSOK D-010 EAC 52 is being revised and an updated table of with acceptance criteria will be available in 2026. Havtil expects that the new revision of Norsok D-010 Rev 6 will clarify the requirements for the choice of geological strata/formations, qualification and use of creeping shale on the Norwegian continental shelf.
Through the knowledge gathering, four operators shared their experience and knowledge. In addition, four service companies provided information about tools for qualification, verification and use of creeping shale as a well barrier element. Two research institutions also assisted with knowledge transfer.
Qualification
For Havtil, it is important to ensure that operators on the Norwegian shelf qualify the use of new technology and new well barrier materials in line with the regulations. This is pursuant to Section 9 of the Facilities Regulations on the qualification of new technology.
The knowledge gathering showed that one operator has qualified the use of creeping shale in accordance with DNV GL RP A203. The other three operators have used Norsok D-010's acceptance criteria as minimum requirements for function and performance.
The four operators on the Norwegian shelf have adopted different approaches to the qualification and use of creeping shale. The choices reflect their operational context and maturity of best practice.
Research and operator experience confirm that the successful and robust use of creeping shale as a well barrier element (WBE) requires formations with suitable material and mechanical properties, particularly high clay and smectite content, ductility and low permeability.
Studies from SINTEF and PUC-RIO, supported by operator data, have improved our understanding of how stress conditions, lithology and well geometry affect whether a creeping formation is suitable for well creep.
Increased P&A activity in the future
The knowledge gathering was carried out by Reflekt, on behalf of Havtil, and concludes that the planning and execution of permanent plugging on the Norwegian continental shelf will require significant resources over time.
The use of creeping shale natural geological layers in overburden or the caprock can be an efficient and cost-effective method of establishing an acceptable well barrier element behind casing in the future.
Havtil expects more research and development of methods and tools for ensuring robust well barriers in the years ahead.