Abstract
As an oilfield reaches its expected End Of Field Life (EOFL), permanent abandonment is required to meet local regulations, specifically for wells where the Floating Production Storage and Offloading (FPSO) vessel has been de-commissioned within the last three (3) years if no monitoring has been performed in this period. However, this abandonment campaign faced well integrity issues, and the mandate from local authorities was to suspend the wells. Using Coiled Tubing (CT) with a Real-Time (RT) downhole monitoring system added value to the operation and its successful completion, saving time and avoiding unexpected events.
The methodology behind this campaign followed customer requirements to either P&A or suspend the wells, depending on the case. A series of inflatable packers were included as a base for cement and/or to cement the A annulus. It was critical to punch the inner tubing to communicate with the A annulus and be able to cement it. CT with Cable (E-line) installed conveyed a punch downhole with RT communication between the surface and the Bottom Hole Assembly (BHA). The RT downhole monitoring BHA was also important for accurately correlating depth and acquiring downhole data such as pressure and temperature to help ensure the correct placement and inflation of the packers and monitoring the cement slurry behavior.
A total of two (2) wells were successfully temporarily abandoned from a Drill Ship using CT to clean, punch, and place cement plugs in the annulus and tubing (using inflatable packers). The remaining wells were suspended according to V0 barrier philosophy, and throughout the operation, faster decisions were possible due to the RT downhole data from the BHA sensors being transmitted to the surface.
The surface equipment and BHA selected for the operation were part of the strategy for faster rig Up (R/U), Rig Down (R/D), and changing from one well intervention method to another when required. This included using a Coiled Tubing Lifting Frame (CTLF) with an injector table to swap from CT to Wireline (WL) quickly while keeping the CT injector and stripper with the main BHA rigged up during WL interventions. The synergy between multiple service lines created an optimal solution by fine-tuning the cement slurry rheology with hydraulic simulations and using a WL punch that was deemed most suitable for the application.
This paper covers the thru-tubing operation to abandon and/or suspend the wells using CT while saving overall time to R/U and R/D for both the CT and WL. It resulted in a more coordinated and reliable operation, avoiding typical problems often associated with P&A in deepwater. It describes the challenges faced and the solutions implemented to address them and complete the campaign's objective.
