Production and Well Access Restored After a Successful Subsurface Safety Valve Flowtube Milling on E-line, Preventing Major Rig Workover

Abstract

An offshore production well was out of operation after unsuccessful inflow tests. A remedial work plan was designed, but the execution resulted in severe damage to the top of the flowtube inside the Subsurface Safety Valve (SSSV), which was bent over and preventing production. Wireline conveyed mechanical intervention was performed with robotic tools to mill the obstruction and regain full bore access. Downhole hardware milling is a common technology; however, a thorough process must be followed in order to succeed. The following factors were among those to be considered: well configuration (completion schematic and restrictions); the material of the flowtube (9CR-1MO Martensitic Steel); the risk of damaging the surrounding area; the risk of rotating the whole assembly while milling; and the risk of getting stuck with the e-line Bottom Hole Assembly (BHA). The milling intervention program was drafted taking into consideration different scenarios including contingencies. E-line conveyed robotic milling intervention was the preferred option due to the urgency of the operation and high accuracy required to ensure the SSSV was left operational after milling. The robotic toolstring was first deployed for a drift run. Subsequent diagnostic runs were executed to help the team understand the downhole situation, adjust the operation plan and to test the performance of the tool downhole. Finally, the milling run was conducted showing a clear signature on the acquisition system, providing the parties involved with certainty regarding the outcome. A camera run was performed to verify the conditions of the operational area after milling. The job was executed in a total of four runs as per the program. Furthermore, the milling time itself was only 17 minutes. The complete removal of the damaged section of flowtube allowed the client to restore production immediately after testing the well integrity, with the SSSV fully functional. This paper describes the complex yet efficient operation where a robotic milling tool, conveyed by e-line, was able to remove a critical downhole obstruction and restore production while preserving all safety features of the well, thus preventing a complex workover operation. The in-depth preparation, followed by a methodical execution, allowed oil production to be resumed in this well.