Complex Operation to Insert Coiled Tubing Through Parted Production Tubing and Regain Pressure Integrity for Plugging and Abandonment

Abstract

At the end of 2020, complex well anomalies were identified in the previously shut-in, highly deviated well A in deepwater Gulf of Mexico. Closely monitored wellbore pressures indicated A/B annulus communication, and remedial slickline diagnostics discovered the tubing was parted between ~4,250 and 4,270 ft measured depth. The abnormal well conditions and the presence of a single barrier on both the A-annulus and B-annulus triggered the well anomaly process, and action was taken to mitigate the risk profile by commencing abandonment operations prior to the start of the hurricane season. The well anomaly risk assessment indicated the highest risk was the single barrier on the B-annulus as it had a history of failures and repairs. The outcome was to attempt to further mitigate the risk profile by commencing zonal isolation operations. To achieve a safe operation, a real-time coiled tubing (CT) downhole measurement system and dynamic interpretation software were used to mitigate the risks involved in accessing the lower section of the parted production tubing, pressure testing the completion, perforating the tubing, confirming the firing of the tubing-conveyed perforating guns, and pumping a balanced cement plug in the tubing and annulus after setting the cement retainer. This study proposes an innovative approach to integrating CT, telemetry, and mechanical wellbore isolation tools to increase operational efficiency. Real-time bottomhole pressure, temperature, and casing collar locator (CCL) measurements proved invaluable by providing the necessary guidance to successfully set the inflatable packer and fire the perforating guns. They also provided pressure confirmation that tubing integrity issues did not allow cement in the A-annulus to escape into the production tubing on to the backside of the CT.