Sakhalin Single Anchor Leg Mooring (SALM) Repair Project

In July 2008, Sakhalin Energy Investment Company (SEIC) had successfully retrofitted its SALM system offshore Sakhalin Island in the Russian Sea of Okhotsk following its Universal Joint (Uni-joint) connection failure in November 2007. This SALM system is part of the “Vityaz” Production Complex in which the produced oil is exported from the Piltun-Astokhskoye-A platform via a subsea pipeline and the SALM to the Okha floating storage and offloading (FSO) unit for subsequent loading onto tankers for delivery to customers. Yearly oil production using the SALM system starts normally in June and lasts till December, during the ice free period. Full year round production were planned using a pipeline replacement for the SALM system (on-stream early 2008). However, in the interim period, there was a significant production opportunity if the SALM could be reinstalled in time for the summer 2008 ice-free season. Another significant incentive for SEIC was an early gas flow through the offshore pipelines to the Onshore Processing Facility for commissioning purposes, which expedites first gas delivery for the whole project by an estimated 4 months. In order to make this production season possible, a unique and fast track project to reinstate the SALM was necessary. SEIC, Shell International E&P in Rijswijk and Single Buoy Moorings Inc. in Monaco, had jointly undertaken this project, incorporating proven engineering standards with an immense amount of creativity to meet these time constraints. The SALM project, that would normally take 2 years, has been hailed as a great success with design, fabrication and installation completed in just 7 months time. This paper describes the key challenges overcome to successfully deliver a fully working SALM system to an extreme time schedule. The emphasis is on a description of the technical challenges and the engineering repair solutions developed with reference to the constructibility, transportation, installation and operation. The challenges include: Re-engineering of the SALM Unijoint cast components to meet the limitations of the available foundries, implementation of a novel pull down installation method using a subsea linear winch, design and construction of independent contingency option, installation trials, worldwide logistics and project coordination. All these aspects form an integral part of the project execution strategy with prompt decision making to meet the required schedule.Copyright © 2010 by ASME