Abstract
The use of access fitting for intrusive corrosion monitoring tools is a common practice in the Oil & Gas industry; however, the Company has faced several difficulties including a recent incident during retrieval operations which has led to suspend, or significantly reduced the use of corrosion coupons and probes, decreasing the frequency of retrieval, and eliminating its use in new projects. In order to reduce the risk, it was decided to decrease 91% the use of corrosion coupons, hence suspending the retrieval activities in those locations. Therefore, more than 300 access fittings / locations were no longer required. These locations, un-attended, might result in dead legs (corrosion threat) which could create a possible leak path in the pipeline systems. In that sense, there was an urgent need to define a safe, efficient and permanent solution for the abandonment of the existing access fittings. Several options were reviewed, considering technical aspects as well as costs. The first option was to use a solid plug assembly with a high-pressure retaining cover; this was discarded due to possible creation of dead leg, thus needing further maintenance / monitoring and as such could not be considered as permanent solution. A second option was to carry out sectional replacement of the pipeline at the corrosion monitoring pit; this is a feasible alternative for pipelines with extended shutdown flexibility otherwise hot-tap & stopple operation would be required for execution with a considerable high cost associated. For the third option, the Company worked with a third-party pipeline isolation specialist to develop an optimal solution which considered the design of a permanent abandonment plug compatible with the existing access fitting that could be installed while the pipeline is in operation with the available service tools. A procedure was developed for the trial of the abandonment plug system to capture the required installation steps and testing criteria (pass/fail). The trial for the abandonment plug system was successful and there is ongoing plan for the roll-out across the pipeline systems. This paper will cover the selected option, including design, factory acceptance test and field trial results.
