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

Abstract Walk-to-work (W2W) concepts are widely used in the offshore wind farms as means of access to offshore wind turbine platforms. This is typically achieved using a Service Operation Vessel (SOV) equipped with a suitable W2W gangway. This system has also been explored in the Oil and Gas industry for temporary access to offshore platforms. However, the use of this system as a primary means of access to operating offshore oil and gas platforms remains limited. When it comes to selecting height of a W2W landing, from basic Naval Architectural hydrodynamic principles 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 of the W2W landing and expose any 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.