Abstract

This paper describes the challenges involved with providing a coiled-tubing (CT) intervention solution from the helideck of a normally unmanned installation (NUI) in the Gulf of Cambay in offshore India.

The project began with a detailed analysis to determine if intervention was practical from the helideck of the NUI, or if barge support or a full jackup-rig intervention was necessary. Some factors in this analysis included the limited deck space, restricted crane capacity, and the existing available utilities. This led to the planning and sourcing of suitable CT, flowback equipment, nitrogen, and fluid-pumping equipment, as well as necessary downhole tools. Trials were performed onshore to optimize the rigup, stackup, and deck layout. The boat loading and lifting plans were created from these trials. The combination of the prejob planning and the trials led to the confidence to conduct this intervention with modified safety arrangements required for the platform when no helicopter operations could be performed.

The purpose of the actual intervention was to complete sand cleanout of the horizontal-well section, isolate the lower oil-producing zone, open a sliding sleeve to access the upper zone, and unload the well with nitrogen to restore production.

This paper also includes the variety of applied technologies that were either attempted or successfully used to bring the well back into production. This required the use of the latest generation of horizontal, downhole-tool solutions, slickline tractors, CT-tool deployment, and contingency operations, which involved a wide range of downhole tools. The results from the intervention and the lessons learned are presented.

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