Improved Through-Christmas-Tree P&A Plug Placement with New Innovative Cementing Methodology

Abstract

When the production of a platform well is no longer profitable, two options are available—either perform permanent plug and abandonment (P&A) or reuse the slot by plugging the original well and sidetracking. P&A requires setting barrier elements in the wellbore to prevent hydrocarbon migration between potential flow zones and to the surface. In most cases, it is financially beneficial to perform as much of this work as possible during an intervention phase before rig operations begin, thus saving rig operating expenses. Most conventional barriers are balanced cement plugs, and setting a cement plug requires a drilling rig to handle the workstring through which the cement is placed, crew, and associated equipment [e.g., blowout preventer (BOP)]. However, the rig time spent performing P&A could be used more productively, such as drilling and completing new wellbores. An operating and a service company developed a method for setting the primary P&A cement plug toward the reservoir without a drilling rig. The cement is set through the Christmas tree using a specialized wireline-set packer as a base and wiper plugs installed on a specialized spool piece to isolate the cement and indicate completion of the job. This paper explains the method and equipment and presents three case studies from the Norwegian sector of the North Sea.