Remote hot tapping in ultra-deep water

Abstract

Statoil has developed a Pipeline Repair System (PRS) hot tap system at Killingøy Haugesund, which comprises five different tools. This master thesis has focused on one tool, the Hot Tap Cutting Unit (HTCU).

Earlier the depth range of the PRS equipment was to 540 MSW, to cover emergency preparedness for pipelines routed through Fensfjorden. The PRS equipment was upgraded to max. 600 MSW in 1994-95 and due to the Ormen Lange field at 860 MSW, Statoil upgraded the PIF (Pipeline Intervention Frame)/HTCU range to 1000 MSW in 2008-09.

The main objective for this master thesis was to evaluate the HTCU system for extending water depth capability to 3000 MSW.

The main purpose of the report was to describe current design as used during the Åsgard Subsea Compression Project (ÅSCP) in 2012 at 265 MSW, discuss general improvement issues, establish the 3000 MSW design basis and identify necessary upgrades for 3000 MSW operation.

The master thesis included performing a literature study on the topic, conduct interviews with people of different professional backgrounds in the industry, reviewing components, reviewing the ÅSCP, evaluating results, reviewing and evaluating improvements to existing design, as well as assessing 3000 MSW upgrade requirements.

The most critical components extending water depth capability to 3000 MSW are the control cards and the reverse pressure differential challenge on seals and drive shaft.