As well production declines in mature fields and becomes unprofitable, operators must shut the wells in and permanently plug and abandon (P&A) them. It is presently estimated that thousands of such wells will require permanent P&A.
Historically, the P&A of wells in the North Sea were performed using either drilling or workover rigs. In many cases, wells drilled from fixed platforms in the North Sea no longer have operational drilling rigs requiring recommissioning of existing facilities or mobilization of workover rigs.
Regulatory authorities in the North Sea have defined standards for creating permanent reservoir barriers for the P&A of wells, which includes requiring a "rock-to-rock" barrier.
This paper discusses an alternative approach to P&A using coiled tubing (CT) processes and techniques to create these permanent reservoir barriers. One process rigged CT up from the drill floor and pipe deck in a conventional fashion. During the intervention, standard milling and tubular cleanout techniques were used to gain access to the reservoir, and then a novel perforating, washing, and cementing (PWC) technique created the reservoir barrier. Finally, an additional tubing punch run was made, and the barrier was tested. In a single, multiwell campaign, 13 wells in the field had successful permanent reservoir barriers created using CT.
This paper illustrates the successful creation of permanent reservoir barriers using CT. Additionally, the paper highlights that using CT can provide economic benefits for creating the barrier compared to more conventional drilling or workover rigs.