Meeting the challenges of rig-less decommisioning
With the rising number of North Sea fields reaching the end of their useful economic life, an increasing number of operators are faced with well decommissioning projects.
Operators have identified rig-less decommissioning of wells as a major cost saving initiative, but this involves technical challenges arising from the absence of a rig and many platforms having limited crane facilities.
The key to success in this market has required the development of a range of equipment and techniques, some conventional and some new.
The first operation, the downhole P&A, can be achieved satisfactorily using conventional wireline and cementing techniques.
A key area to achieving a rig-less capability is the retrieval and handling of Xmas trees and tubulars. Various means have had to be devised for lifting and severing multiple casing strings. These techniques include hydraulic jacking, tension rings, drilling & pinning of casing strings, and use of band-saws to cut multiple casing and tubing at surface.
In 1990, to provide a cost-effective alternative to using a rig to mechanically cut cemented multiple casing strings at the seabed for the Phillips Maureen project, Claxton developed abrasive cutting technology, which is now offered to the market as the Sabre TM system.
The first North Sea production wells to be decommissioned rig-less were probably those decommissioned over 9 years ago on the Esmond and Gordon platforms in the SNS. Since then, Claxton, who undertook the original Esmond & Gordon work, have been involved with the well decommissioning of over 60 North Sea platform wells, in most cases, without using a drilling rig or a platform crane.
As records now show, with an innovative approach given to rig-less well decommissioning projects, the cost savings achievable, compared with rig-based operations, are significant and provide a strong driver for this market.
This rig-less well decommissioning capability has developed dramatically over the past 5 years to meet the growing need for safe, low-cost well decommissioning services, and as an added benefit has created related opportunities for slot recovery / redrills, rig-less tubing recovery workovers and subsea band-sawing of pipelines.