Significant Time Reduction and Cost Savings Realized Through the Use of Wireline Deployed Milling Services, to Enlarge a Tubing Hanger

Abstract

A producing well located offshore Congo was equipped with a TRSCSSV which failed to open. A velocity valve, with a stem beneath, had been installed to keep the flapper open. This condition, apart from restricting the production, was a temporary solution as defined in Eni's (the operator) well integrity policy; for this reason, the SSV had to be replaced. In order to do so, the completion needed to be removed, which implied cutting the cut-to-release packer. A lock open tool needed to be run in the SSV to allow the cutter to reach the packer. The lock open tool was too big to pass the tubing hanger. Eni issued a challenge to the service industry, to come up with a solution to enlarge the hardened tubing hanger while preserving its mechanical integrity. The solution also had to be deployable quickly as the drilling unit could incur costly standby. The retained solution used a wireline deployed milling toolstring equipped with a diamond coated bit. The benefits of this solution impacted several areas: the surface read out system allowed for fine control of the milling operation, the combinability of the tools allowed for adequate planning of potential fish recovery while retaining well barriers on a live well and the size of the equipment allowed for a rapid overseas mobilization. The milling operation was completed in a single run, with a total milling time of 1hr 47min. The paper will discuss the project scope of work, equipment preparation and job execution, an estimate of the risk and cost reduction delivered, and an estimate of the added production enabled by removing the failed SSV.