Design and reliability analysis of accommodation work barge mooring configuration at a tension leg platform in Makassar Strait, Indonesia

Abstract

An Accommodation Work Barge in Makassar Strait attaches to a Tension Leg Platform (TLP), a floating offshore platform operating in deep-water oil and gas field for a well intervention project. The mooring system are tied up to the north mooring lines of the vessel, whilst hawsers from the TLP connected to the south lines of the vessel. The TLP is fitted with two “TH” lines on its south side. However, these “TH” lines fail due to the unknown reason. The purpose of this study is to evaluate mooring performances to support the TLP operation by using API RP2SK recommendation, which suggests line tension limit, TLP offset, and minimum clearance between facilities. This study assesses reliability index (β) of the recommended design to evaluate whether the TH lines are required or could be eliminated. Mooring analysis is performed using ORCAFLEX for intact and damaged condition, while Monte Carlo simulation is performed to get system failure probability with minimum breaking strength ratio (%MBS) as required parameter. From the results, it is found that TH lines could be eliminated, as they do not affect significantly to the system. The analysis delivers a very secure index (β=14.676) with probability of failure below 10-5.