Session: 01-01-01 Offshore Platforms - I

Submission Number: 152686

Case Study: Munin Unmanned Platform Walk-to-Work Landing Elevation Design Considerations 

Walk-to-work (W2W) concept is widely used in the offshore wind farms as means of access to offshore wind turbine platforms. This is typically done through a Service Operation Vessel (SOV) equipped with a suitable W2W gangway.

This system has also been considered in the Oil and Gas industry where temporary access to an offshore platform is required. But use of this system as a primary means of access to an operating offshore oil and gas platform has been limited.

When it comes to selecting height of a W2W landing, from basic Naval Architectural hydrodynamic principals one can expect height of a W2W landing from sea level to have an inverse relationship with operability of the SOV gangway [1]. As such, the lower the W2W landing, the higher the SOV gangway operability. However, lowering the W2W landing, potentially exposes the W2W landing structure to extreme design wave loads (e.g. 10,000-year return period design waves). Loss of W2W landing to an extreme wave event could jeopardize further accessibility and expose subsea infrastructure to risk of dropped objects.

This paper is intended to summarise results of an assessment where height of the “Munin” fixed offshore platform W2W landings with regards to SOV gangway operability is optimised. In this study effect of W2W landing elevation from mean sea level in relation to SOV gangway operability is quantified for the Munin Platform site specific conditions. Further, a qualitative evaluation is presented to show how benefits of raising W2W landings outside of the extreme wave load envelop outweighs the marginal SOV operability improvement due to lowering W2W landings elevation.

Presenting Author: Mohammad Hajiarab Aker BP ASA

Presenting Author Biography: Mohammad is the Lead Structural Engineer and Structural Technical Authority Delegate for the Munin Topside platform, which is part of the Aker BP's Yggdrasil development, offshore Norwegian Continental Shelf.
He is a Ph.D. qualified Naval Architect from Newcastle University and has more than 20 years’ experience in design, construction and decommissioning of offshore Oil and Gas floating and fixed production platforms.